Science topics: OpticsColor
Science topic

Color - Science topic

The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.
Questions related to Color
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I need to prepare colour tiles (approx 3*3mm with a uniform color) that were stored in sRGB color space for printing out on a litho printing machine (CMYK U.S. Web Coated (SWOP) v2).
However, when I use the seperate+ plugin for GIMP to change to CMYK, the output changes the colors sometimes dramatically. I'm aware that the CMYK color space is more limited than the RGB space, but is there any way to keep the colors more consistent?
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That relates to color management. We need to match the ICC profile of the file and output device. Some graphic software such as illustrator, will have the profile match setting and output preview.
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I'm now working on the mechanochromic material. Base on the concept, the color of spiropyran in the main chain of semicrystalline polymer should be change by stretching. I've tried by using poly(caprolactone) containing 1',3',3'-trimethyl-6-nitrospiro[chromene-2,2'-indoline]-5',8-diol in the middle, but I can't see the mechanochromic phenomenon during stretching by Universal testing machine at rate 1mm/min as reported. How should I do? What is my mistake?
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How did you make sure the spiropyrane is linked to the polymer chain via both OH groups? How did you synthesize the mechanochromic material?
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I am trying to test how effective an app is at reducing the amount of blue light on computer/cell phone screens. So far, I've found that I could potentially use a Chroma Meter to do that (compare readings with and without the app running), but I may not have access to one in the nearby future.
Does anyone know of any other methods that can be used? Any help will be very appreciated!
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Any spectroradiometer covering the visible range would be most useful for this. But if you don't access to that a normal digital camera can also be used as a "color sensor". You might not know the exact spectral response, but it will give an indication of the change.
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I want to know whether there is any difference in EEG signal for Red, blue and green colors and can we differentiate them through some classification algorithms?
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Thank you KL for the answer. For example, I show three colors (RGB) on screen and record EEG signal. Is there any difference in the EEG signal for these three colors?
Can you recommend me some article related to this issue?
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Hello, i would like to know the procedure/ method or any relevant information for obtaining and transferring phase information of a color image onto a metasurface. I have read some literature on monochromatic image recording on metasurface, how is the treatment different for a color image?
Thanks in advance.
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Thanks Raju,
is this a book or an article paper, kindly send me the title please.
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like voltage values to RGB ( 255,255,255) values.
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Do I understand your question correctly? You have light sensitive equipment which results in a voltage signal proportional to the light intensity. Such(Similar) devises are usually used for the measuring the solar light intensity (pyranometer). Unfortunately due to the summation above all energies ("wavelengths") the spectral information is lost. The publication contains some details for absolute and wavelength correction.
Hence the answer is “No”.
You may use a diode array detection unit to analyse the colour (wavelength). Additionally you can use “ciewi wavelength picker” or similar program to calculate the RGB colour.
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I need to find the exact color temperature value from image's RGB matrix value. I am able to find the x,y as well as u,v (chromaticity space) average matrix values. i am working in labview
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Rosemary,
If you know the wavelengths of the RGB reasonably well, fit them to a blackbody curve, and adjust the temperature of the blackbody till you get a minimum in the deviations from the curve to each of the wavelengths.
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Any image processing expert. 
Would it be prudent to say :
(intensity of yellow = 1- tristimulus value of Blue)
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The last formula has an error because is without -1, namely:
yellowness= S*max(( cos(u)-cos(a))/(1-cos(a)) ,0)
References:
1. Vasile Patrascu, New Framework of HSL System Based Color Clustering Algorithm,
The 8th Conference of the European Society for Fuzzy Logic and Technology (EUSFLAT 2013), pp. 416-423.
2. Vasile Patrascu, New Fuzzy Color Clustering Algorithm Based on hsl Similarity, Proceedings of the Joint 2009 International Fuzzy Systems Association World Congress and 2009 European Society of Fuzzy Logic and Technology Conference, Lisbon, Portugal, July 20-24, 2009,  pp. 48-52
3. V. Patrascu, Fuzzy Image Segmentation Based on Triangular Function and Its n-dimensional Extension, in the volume Soft Computing in Image Processing. Recent Advances, Series: Studies in Fuzziness and Soft Computing , pp 187-208, Vol. 210 , (Eds.) Nachtegael, M.; Van der Weken, D.; Kerre, E.E.; Philips, W. 2007
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How to find color  chromaticity coordinate and CIE chromaticity digram by using PL emission spectral data.
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Dear Faizan,
I find GoCIE software is better to plot CIE diagram its quite simple and easy check this link 
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I extracted soil samples from rice paddy long-term experiment by KCl10% after 4 week-anaerobic incubation (30 degree Celsius) and found that extract solutions of samples since 1983-1990 had been turned red, while the 1991-2014 samples were normal. The Iron seemed to be the cause, but why it didn't change in the other samples.
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Do you mean that the extracted soils or their extracts turned red?  Please also give us more information about the soils and their storage conditions.
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I am working in a project and I am confused how to build a system that can select plastic bottles by color.
I will be thankful for your support.
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I will not tell how to make because external components as USB camera, special light and a lot of code lines is needed. Instead of starting building from null better use well known systems, eg. as added pdf. Of course, there are many of them - depending size, IP class, resolution, price. But of course if You want, you can take into consideration Arduino TCS 230 or/and TCS3200D. And again - it is kind of DIY system, but if You do not want to write code always electronics such as 'light to  frequency' converters may need your requirements: http://www.sparkfun.com/datasheets/Sensors/Imaging/TSL235R-LF.pdf which is working perfectly with DiscoVery 32 (STM32Discovery). Systems of  DiscoVery and/or Arduino should  cost less than 200 EUR.
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In Turf grasses Color is normally determined by a Scale from 1-9, given by Beard, If i want to make a new scale and use for Turf Color determination, for example, from 1-8, it is possible ??? Can I use.....
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 Dear Muhammad
In general, nothing is impossible. However, the question is, why?... 
It is unclear from your question what is a reason you want to use your own scales and why do you try to avoid the common aproaches...
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Is there any way by which all the 3 colour planes can be encoded in the another RGB image. Of course number of pixels play a role but i have not come across anything pertaining to this particular way of encoding.
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Can you explain me how to do that in matlab?
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I want to known the difference in color measuring between L*, a*  b* and L*,  C* h*
For my experiment, I used L*, a* b* for measuring the color values of gelatin powder. Anyway, reviewer comments that  "With respect to color analysis, instead of showing L*, a* and b* parameters to characterize the samples color, I suggested to present as L*, chroma coordinate C* and hue angle. The C* parameter is interesting because it shows saturation color, and hue angle expresses the object color."
So, what is the best way to  respond?? Thanks
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 Jamal,
I cannot add to Benedict and Miguel responses -- both provided great answers. My intent is to just add a couple of comments.  Calculating Hue angle can be tricky and Miguel's clearly highlights the issue with his formulas.  The reviewer is right on in asking about for C and H. My years of experience in measuring meat color would suggest that you do not get the "full story" of your color measurements if you only compare samples/treatments using L*a*b* as C and H can give you a more "global" perspective of your experimental variables. From a practical point you likely will find 1 or 2 of these measurements will be very good for characterizing your gelatin samples.
Here is a guide that might serve as a good reference:  The "AMSA Meat Color Measurement Guidelines".  Its a free download from the American Meat Science Association at:  http//www.meatscience.org   Then search for the guide.
Best of luck with your work!
Does light have any effect on the growth of pigmented bacteria colony?
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I'm currently culture colored pigmented bacteria on NA. After a while, I notice the color of the colony disappear. Hence, I would like to know if it has something to do with light because I just place my plates on the bench (with normal exposure of the laboratory lamps during the day).
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definitely light have impact on growth of the pigment producing bacterial colony.
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 thank you for help When a beam of light is illumated to a LCD screen (such as the television),we can see colorful light ,why?
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 Hello
Sudarson S. Sinha
Thanks for your link, I have understood the constructure of the LCD tv .
as its explanation , the caculator screen is similar to the TV or phone screen, but why i can't see the same patten using the caculator screen(use a beam of light illuminate the screen from outside)
And i also want to ask, the link said when there is electrictiy , the screen is dark , do you think this resonable?
really thank you
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HI All,
I'm fairly in new with R, so any help is much appreciated. I'm in the process of making a heatmap using the pheatmap function. I'm adding a column color bar so that I can associate specific data in the header with specific colors in the color bar. So for example I want anything that contains the number 1 in the header of my entire data set to be labeled as Male and have a specific color associated with it in the column color bar.
I'm using the following code as an example to try to do this:
require(pheatmap)
# dummy data
dummymat = matrix(rnorm(100), 10, 10)
colnames(dummymat) = paste("Patient", 1:10, sep = "")
rownames(dummymat) = paste("Gene", 1:10, sep = "")
# create a data frame with the patients categories
categories <- data.frame(Sex = factor(sample(c("1", "2"),size = 10,replace = T), labels = c("Male", "Female")), Stage= factor(sample(c('Patient10','Patient9','patient5'),size = 10,replace = T), labels = c('I','II','III')))
rownames(categories) <- colnames(dummymat)
pheatmap(dummymat, color = colorRampPalette(c("navy", "white", "firebrick3"))(50), clustering_method = "mcquitty",
clustering_distance_rows = "euclidean", clustering_distance_cols = "euclidean", scale = 'none', annotation = categories)
Obviously from the above code I don't get what I want. I'm sure I using the wrong functions here to do this (since I'm a beginner in R)
Can anyone help with my question? I would really appreciate any input and help that anyone can give.
Thanks,
Afshin
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Please take a look at these codes. I used 'aheatmap' function from library(NMF) instead library(pheatmap).
Is this what you want? The heatmap is attached.
You can also eliminate the dendrogram by replacing Colv=TRUE, Rowv=TRUE with Colv=NA, Rowv=NA when run the plot.
set.seed(1818)
library(NMF)
library(gplots)
dummymat = matrix(rnorm(100), 10, 10)
colnames(dummymat) = paste("Patient", 1:10, sep = "")
rownames(dummymat) = paste("Gene", 1:10, sep = "")
categories <- data.frame(Sex = factor(sample(c("1", "2"),size = 10,replace = T),labels = c("Male", "Female")), Stage= factor(sample(c('Patient10','Patient9','Patient5'),size = 10,replace = T), labels = c('I','II','III')))
rownames(categories) <- colnames(dummymat)
## set up the colors to use in the bars above the heatmap
annot.color.col <- list('Sex'=c('blue','yellow'),'Stage'=c("green","red","gold"))
outf <- 'beheshti_plot.png'
png(file=outf, height=600, width=600)
aheatmap(dummymat,
         Colv=TRUE, Rowv=TRUE, labCol=colnames(dummymat), labRow=rownames(dummymat), cexCol=1,
         annCol=categories, annRow=NA, annColors=annot.color.col, annLegend=TRUE,col=colorpanel(20,'red','green','blue'),
         scale='none', main='Heatmap via aheatmap in library(NMF)')
Does the color of dental composites changes during light curing?
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Does the color of dental composites changes during light curing? If yes, what could be the possible reasons?  The energy provided by curing light makes any chemical changes other than polymerization that can alter the shade of restoration. The shades (such as A2, A3) correspond to uncured or cured resin materials? Related articles are highly appreciated, regards.
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Certainly there is a slight change from the uncured and cured state, in terms of translucency. However, shade transition largely depends on the zone of application and layers applied. Shall look into the refernces and update soon.
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How to decolorize Aloe vera extract using for any herbal formulation? It need to be run in semi preparative hplc. I am scared the coloured compounds might spoil the column, i am not sure of it but. Can someone answer both the questions?
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Have you tried active charcoal. If needed use centrifugation to separate charcoal particles.
Or use solid-phase sample preparation columns with C8 or C18 coupled to silica.
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Dear all
I plan to do experiment that subjects look at some colors in display. At the beginning, I want to do gamma correction for display. I want to know gamma table or how to do gamma correction for display, especially RGB. My operating system is windows7.
Regards
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I am using a Leica DM4000B microscope with LAS V4.0 software. 
I am trying to obtain images of cells in liquid-rock powder cultures, but I come across two problems regularly which make it very difficult to visualize cells: 
1) non-specific binding. I believe that the clays within the shale rock that I am growing my microbes in are binding to the dye and causing it to auto fluoresce.
2) Background fluorescence.
See the two attached images. Both are images using Acridine Orange dye. The first is a good image obtained by having the cultures on a black polycarbonate filters and I happened to find a good region to image. The second image is what I commonly get.
Can anyone suggest image filters that will filter out the auto-fluorescent orange colours and enhance the green colours of my microbial cells?
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I agree with Maria, there are several image processing softwares available in the market which have the option of using filters to normalize or substract background/autofluroescence. However, its important to obtain high quality digital images. Use of averaging of images and nyqvist settings would help you to a certain extent. An indispensible part of an biological image to have some background. As long as your image have pixels in the quantifiable range (between under and over saturation) and have no spectal overlap, the image can be processed efficiently and quantified. Also be aware of your dyes, for instance emission spectra of acidine orange could vary depending on the contents of the cell (high DNA or RNA) and may overlap with GFP.
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Thanks in advance for your replies.
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I am agree with John Seymour, colour strength is frequently computed as ratio of K/S values beside calculations based on tristimulus values or Gall formula (B). Nevertheless in industry is preferable method based on K/S weighted at each wavelength by the standard observer x , y , and z bar function. This weighting version is called as "integral Strength" in comparison to "inter Strength", which uses K/S, weighted at each wavelength by the Illuminant/Observer data. This results may better correlate with your visual evaluation of the sample than does either Sum K/S. If we will go back to colour strength computing, you will use two steps (in some cases three steps) procedure. Firstly you will obtain weighted K/S by using of following formula: fk = Σ(K/S)λ . (xλ+yλ+zλ) on interval of wavelengths 380-760 nm or reduced range 400-700 nm, than you will calculate colour strength CS = C1/C2 . fk2/fk1 . 100, where index 1 is standard dye and index 2 is tested dye. In above mentioned three steps method is on the and used adjustment of tested dye concentration on the same colour strength as standard dye followed by calculation of so called "residual" colour difference, which is known disadvantage of this method of colour strength adjustment. 
In your case it is possible to use CS for evaluation of dyeing process effectiveness or modification of dyeing procedure.
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To convert to rg Chromaticity from RGB is fantastically simple:
r' = R/(R+G+B)
g' = G/(R+G+B)
b' = B/(R+G+B)
There is now no luminance value, I would like to further remove the saturation from each element in the hopes to end up with a three-component hue value.
r'' = f(r', r'g'b')
g'' = f(g', r'g'b')
b'' = f(b', r'g'b')
Does anyone know of how to approach this? Chromaticity is both hue and saturation so there must be a way, something that does not end up with the HSL/HSV single-value hue. I know CIE Lab gets to hue from atan2(b,a) but again it is a single-value in degrees (0-360).
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There are two valid answers here. The first point is that you need to be specific on the type of RGB values in question. If they are just monitor drive values the calculation is specifically for that screen and it has no wider significance. The basic properties of the  r,g plane of the  monitor colour space are however sufficient to reveal the R:G:B ratio that defines your Hue. The problem of course is where is your b value  coming from?. Given that r+g+b=1, then r =1 represents pure red gun colour etc. It follows that pure B must be at r=g=0 i.e.at the origin in the r,g diagram. likewise the b value is calculated by b = 1 - r - g and the ratio r:g:b then specifies your Hue.
The second answer is device independent. There is a widely recognized  colour space used in imaging known as sRGB space where the R,G and B hues have an unambiguous device independent definition and the same derivation applies. The ultimately precise r:g:b ratio for any given screen colour may also be back calculated from measured CIE XYZ co-ordinates by matrix multiplication.
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Most of the publications are in German that could not read or understand. I am basically searching for a method to produce trichromy starting from the origins. 
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You can read for example the book: Hans G. Vælz  Industrial Color Testing. Obviously is used comparison of SUMs of K/S, alternatively weighted K/S by standard observer function. Other way is based on colorimetric data, for example Gall method, which is based on DIN6164 color space.
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I have collected spectra using a spectrophotometer and can see which wavelengths of light are absorbed/transmitted, but how do I translate this to a single colour? 
I have also converted the absorbance values at each wavelength to RGB and HSV values, so, if easier, is there a way to combine RGB/HSV values to one resultant colour value?
Thanks,
Cat
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Hi,
 As a first step, you basically need to calculate how much the spectrum you measured excites the 3 human photoreceptors. In principle, you need the spectral sensitivities of the 3 human photoreceptors, L, M, and S (long-, middle, and short-wavelength). However, depending on what you want to do with your colour specifications, you can also directly calculate the Tristimulus Values (XYZ). XYZ allow you to directly calculate chromaticity coordinates (xyY), which are widely used to communicate colour specifications.
If you want to obtain LMS values you need to get spectral sensitivities (cone fundamentals). If you want to get XYZ you need colour-matching functions (CMF). The CMF are – in principle - a linear transformation of LMS for the purpose that one dimension (Y) corresponds to luminance (i.e. low-level lightness). For further details see e.g. here http://cvrl.ioo.ucl.ac.uk/database/text/intros/introcones_cmfs.htm. You will find cone fundamentals and CMF here http://cvrl.ioo.ucl.ac.uk/cmfs.htm and here http://cvrl.ioo.ucl.ac.uk/cones.htm.
Both consist of 3 columns with the contribution of each wavelength to the cone excitation (LMS) or XYZ, respectively. You just need to calculate the sum over all wavelengths (i.e. the integral) to obtain how much your spectrum excites each of the cones / each of XYZ. This can be done by an inner matrix product (= sum of products). So, in principle you need to do this:
SPECTRA(:,1:3)'*CMF(:,1:3)
where the rows of each matrix (SPECTRA & CMF) are the weights for each wavelength.
 However, you also need to make sure that your spectrum has data for the same wavelengths as the CMF/cone fundamental. If not, you will need to interpolate your spectrum for the respective wavelengths of the CMFs (either linearly or by cubic spline). Moreover, in order to get standardized XYZ you also need to multiply by 683 (=maximum photopic luminous efficacy) and by your wavelength resolution (the wavelength-interval between each data point, e.g. 300:5:800nm à interval = 5nm). Once your CMF and spectrum are matched for wavelengths, the complete formula looks like that:
XYZ = SPECTRA(:,1:3)'*CMF(:,1:3)*683*Interval;
Then you obtain xyY by normalization (x = X./(X+Y+Z); y = Y./(X+Y+Z); Y=Y).
A final complication: All I said above requires your spectra being specified in spectral radiance (w/sr/m2), as measured by a spectroradiometer. However, if you measured photon catches by a spectrophotometer you first need to calculate spectral radiance in order to get XYZ.
All the best,
Christoph
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I want to use color information for using  traffic sign recognation. But the color effected from illumination for example red color looks like black color. I think maybe color normalization help me. what can ı do?
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If I'm reading your question right, you're interested in what color different signs appear when illuminated using illuminants which have vastly different colors; the example is that a red stop sign will appear dark when illuminated using a source which is predominantly blue.
The traditional way to transform between different illuminations is to use the von Kries transform. It models the way human eyes respond to different illuminations. It's not perfect (human vision is complicated, and color spaces usually use three values to approximate the spectrum!), but it will get you close. [Hint: when you're transforming the colors, remember to convert your pixel values from sRGB to linear RGB first.]
Bruce Lindbloom (linked below) has great information about the von Kries transform and color adaptation when viewing scenes under different illuminations.
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We want to measure CIELab values in liquid samples using the reflectance spectrophotometer, and we are not sure about how we could do it having reliable results. Have any of you tried using the Konika-Minolta CM-600d with a CM-A514 Sample Holder and a specific cuvette? Any other options? 
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The conversion from spectra to CIELAB can easily be done. I can provide a spreadsheet, if you need it.
Doing the conversion in a way that makes sense for your application is a bit harder, since the measurement that a transmittance device includes only a single pass through the liquid, and viewing would generally involve light passing through twice. Also, the viewing color will include the color of whatever is behind the liquid.
Am I understanding the question?
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Im interested in qualitative measuring the temperature inside the plastification chamber of a plastic injection molding machine. I have founded some irreversible thermocromic picments but they change thei color at low temperature (0-150 celsius degrees). I am very interested in products that change their colour at higher temeperatures.
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Dear Joauin
Tempilstic crayons may be the answer
www..tempil.com
. I have used them to assess the evenness of heating in textile fabric dying machines. each item has a specific melting temperature and once melted,  the colour change is semi permanent. the temp range is 100 to 2000 F
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Dear All,
I irradiated some organic samples with X_ray and observed color change but not chemical change in the compounds. How can I justify this color change? Does the color change mean any alterations or decomposition?
Thanks,
Sevan
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You always ionize atoms in your sample when irradiating them with X-rays. For low-Z elements this may also mean, that you directly break or alter chemical bonds. Especially organic material may react with color change. I have seen this in precious stones and also parchment, which - by the way - was a reversible process. Especially when using high fluences (f.e. synchrotron excitation) the monitoring of radiation damage is mandatory and the often claimed non-destructiveness of X-ray techniques is not strictly correct.
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In between the first look to critically ill or severe injured patients, the evaluation of the colour of the skin is one of the immediate available informations and gives us a first impression of the patients condition.
The limiting fact is, that the evaluation is not objectively and is depending on light or subjects...
I want to know, if there is any method available to verify the skin colour (whitness, paleness) objectively?
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Hi Mark,
We provide a specific device to do so, called C-Cube and specificaly designed for clinical research. It provides reliable measurements of skin colours in Lab and sRGB colour spaces.
Best regards.
Alexandre
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Please explain the chemical preparation to color change and digestion, diatilation and titration ? So many times color do not changed .
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Is there any other method to do nitrogen analysis?
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Can somebody suggest an up-to-date method to transform reflectance measurements into variables of hue, chroma and brightness? Thank you!
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Since the road from reflectance data to subjective colour attributes has severals stations inbetween, I wondered for which step you seek an "up-to-date" method. While CIECAM02 is the latest development in colour appearance models, it starts with the tristimulus values of a colour sample, which thus have to be calculated first. 
Assuming that you are talking about *spectral* reflectance values you first must know the spectrum of the light source that is reflected from your patch. In a nutshell you first have to multiply those two spectra with each other, then you have to apply three different weighting functions to the result, and finally you have to integrate (sum up) these latter three results in order to find the tristimulus values X,Y,Z of your colour sample under the given illuminant. Only then you can proceed with the CIECAM model.
You might know all this, but since the exact method of calculation has always been a matter of debate, I thought I could mention that there is a standard from 1994 available detailing the procedure (see attached file).
ps "brightness" is often understood to be the subjective correlate of the luminace of a light source. It may be that "lightness" is what you are after, which is an attribute of a coloured object that varies between the extremes of black and white
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“participants rated the vividness of colour experiences and selected specific colours in response to a set of graphemes (letters/sounds like ‘S’, ‘U’, ‘OO’) and sounds in L SD and placebo conditions. Participants also independently completed measures of absorption and visual imagery” (Terhune et al. 2016). Is that a good measure for “experience of drug-induced synaesthesia-like experiences”. LSD volunteers are not reliable because they’re in no uncertain terms behaving unpredictably. The evidence suggests they are in a disorganised, creative, and free roaming state of consciousness (Kaelenso et al. 2014) to use any type of self-assessment would be fraught with subjectivity and miscommunication through their own sensitivity to emotional states and others, this is related to atypical experiences under the effect of psychedelic drugs. I don’t think it is feasible to test highly sensitive individuals, in lucid dream-like states of mind under controlled experimental conditions without controlling for said conditions, we would ideally need a condition control group as well as a placebo control condition group, although in my opinion a placebo control isn’t necessary because we are aware the drugs are having a distinct effect and do not need confirmation that these effects are not being caused by placebo effects. What we need to account for is the set and setting, the old idiom of many experienced users of psychedelic drugs, including but not limited to culturally relevant rituals, such as you may refer to in shamanic practices. Although these rituals are highly relevant in western societies too, referring to Free-Masonry practices where ritual is highly relevant in inducing specific states of consciousness.  
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I would like to relate Huston Smith's observation that classic placebo-controlled studies are ineffective, I would even say irrelevant, in psychedelic research since it quickly becomes apparent to all involved, subjects and researchers alike, who got the placebo and who got the psychedelic agent (he made such a comment after having been involved with the original Good Friday experiment). Moreover, such studies stem from the ethos of reductionist-materialist scientific practices - which are of value in clearly materialistic sciences like chemistry, for instance - in which the fantasy of "objective" science can be approximated. Ultimately all data obtained from experimentation must be interpreted by human beings, who are subjects. As I say this approach has practical value within the parameters of the Newtonian scientific worldview, which has been of enormous value in consensual reality; but becomes irrelevant, even ridiculous, to one who is in a psychedelic state. Not only are their rational communicative capabilities impaired - the observation of an outside observer - but their valuation of participating in such a study becomes laughable in their alternative/expanded state of reference. The research of Claudio Naranjo or Stanislav Grof, for instance, is more relevant. Here, a highly trained scientific observer of those in psychedelic states apply a qualitative analysis, which can really only be conducted after acquiring a significant corpus of experience and acknowledging that subjects can evaluate subjects only within a tentative theoretical framework - the ideal of true science in any case, where theory must be endlessly revised to match observation. Also, as Mr. Marks observed, synaesthesia is a fairly infrequent feature of psychedelic states.  Further, experiments meant to observe particular outcomes in psychedelic states cannot be crafted by design due to the highly individualistic nature of the entheogenic experience. I should mention my bias: I am a psychologist focusing on consciousness studies, which can only be a qualitative interpretation. This does not preclude rational and scientific study, but it does preclude the reductionist gold standard of objectivity and unswervingly reproducible outcomes.
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Would I be able to determine the frequency of resulting 'average hues' using the information provided? and how?
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yes, but is it possible to obtain frequency in Hertz?
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Hi All,
I have question about colocalization analysis for 3 channels. I attached an image to make my questions more easily understand. I have 3 images by confocol, from 3 channeal, green, red and blue. I want to measure the colocalization for red and green,(which will be yellow after merge image), however, I want to check the rate between this yellow part/blue. The software by leica can only analysis 2 channels, this really drived my creazy, any help on this would be very appreciated.
Thanks!
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Hi Monica,
An other alternative is CellProfiler, which has multiple modules to measure colocalization depending on your experiment or images. We used it for a large amount of confocal images and the results were quite reliable compared to manual evaluation in AxioVision. You'll find more details and an example pipeline at http://cellprofiler.org/examples.html#Colocalization
Best,
Daniel
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Dear Researcher,
I would like to understand and enhance the color image contrast. I have somme questions to ask, i will be very appreciated if you answer me.
1. What does mean"high  dynamic range" and " high contrast"?
2. Is the image contrast affected by the illumination? 
3. To enhance the contrast of color image, i use the Retinex algorithm to decompose the image into illumination and reflectance images. Then, i enhance the contrast from the illumination image.
3.1 Is is correct to enhance the contrast of illumination image.? If so, what kind of images that we can apply this idea?
Thank you.
Best Regards
Khadidja BELATTAR
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1. What does mean"high  dynamic range" and " high contrast"?
High dynamic range means that the image has an higher range of luminance values (The intensity of the image). 
High contrast means that the difference between luminance /colors in the image is big.
2. Is the image contrast affected by the illumination? 
lets denote two pixles in the image P1 = (x1,y1) and P2 = (x2,y2)
Contrast(P1,P2) = abs(luminance(P1)-luminance(P2))
luminance(P1) = Illumination (P1) x Reflectance(P1)
so changing the Illumination(P1) by a different amount than Illumination(P2)
will effect the contrast between the two points.
3.1 Is is correct to enhance the contrast of illumination image.? If so, what kind of images that we can apply this idea
enhancing the contrast of the illumination will enhance the contrast in the image. Is it correct it depends for what application. I think for low contrast images it can have a good effect. 
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White and coloured bodies have enough energy so reflect out excess while Black bodies have low energy and so have enough room to absorb all and reflect no light.
Is my hypothesis correct?
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First of all, white is not a color, it is a mixture of all the colors. The Sun light is close to white, and we can see its composition when passing a beam of Sun light through a prism. 
Second, color of objects is due to the wavelengths that these objects reflect.
When an object is illuminated with the Sun light, some wavelengths are reflected, others absorbed, and others are partly absorbed and partly reflected, with different absorption and reflection coefficients.
Black bodies have an absorption coefficient close to 1 (at least theoretically) for all the wavelengths.
The color of the body is therefore given by the mixture of reflected wavelengths, each wvelength with the respective reflected intensity. Thus, so far, the question "how much energy contain the atoms of the body" is not connected with the phenomenon examined.
However, if the atoms of the object are highly excited and emit photons, e.g. in an incandescent object, the color of the body changes according to the emitted wavelength. So happens with stars. They emit light, the reflected light is negligible.
No doubt that the photons in the blue part of the spectrum are more energetic than photons in the red part. However, to say something about the energy of the atom, is not simple, because the energy of an emitted photon is the difference between two levels. An atom may be excited to a high level, but the highest emission probability may be to a very close level. To the contrary, an atom excited to a level not so high may emit a photon and fall to the ground level, s.t. the enery of the photon may be bigger than in the former case.
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I have an image, from that image I have to extract 64 dimensions visual vector. So, anyone can tell me how to do this ?
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A simple approach could be to create the 64 dimensions from the three HSV channel histograms, e.g. 16 from the hue channel, 16 from the saturation channel, and 32 from the value channel. For each of the channels you have to calculate a normalized histogram with the corresponding resolution (i.e. 16 bins for the hue histogram, 16 for the saturation histogram, and 32 for the value histogram). The total of 64 histogram values constitute the visual vector that can be taken as a fingerprint of the image, e.g. for classification purposes.
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Do you always work with image processing for converting color images to GrayScale?
when a camera connect to Fpga and camera captured the image and sent to fpga ,  here's  should image color to grayscale too ? Or just in the Matlab?
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Grayscale images are more suitable for certain applications eg Image Steganography etc and when the image is in rgb format and our application needs a grayscale image then only we use the rgb2gray conversion, not always. When we are working with color image processing we need not to use rgb2gray conversion similarly if the image is already in grayscale.
As appropriately pointed out above, some times working with a single channel (either R or g or b) also can help and no need of conversion again.
I have no idea about fpga and hdl !!
i usually refer the image processing book by gonzalez. 
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the screenshots are the after ORB mathcing is done as you can see even the second image got mathces which is wierd and I cannot distingusih the images.
Test 1 and test2 are the two images that I want to differentiate.
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Do you mean why ORB algorithm gives matching result even for totally different images?
Two different images still have similar features and ORB is only give you the matching point. In my opinion you want to do image registration. this kind of error can be solved by additional process (e.g. RANSAC ). The related documents are listed below. Hope this helps.
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in a predetermined time period -say half a year or a year the change should be an intrinsic property -with no dependence on external factors. Preferably -it should be a material that can be laminated
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All natural pigment from animals can fade easly with ageing or under the action of light
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My question, in other words, is: when we see an object of different colours, does every colour cause the same frequency in the corresponding activated cone? 
Does every qualia (yellow, red and so on) have a particular frequency and/or amplitude, or all the cones fire with the same frequency (of course, when the stimulus is kept constant and regular)? 
The difference between, say, the red and the green is just qualitative in the retina and in the brain, or it might be quantified?
Thanks!
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your question "The retina contains L cones, M cones and S cones: when they are activated, do they fire with the same frequency?"
No.  Check out the following chapter if I have understood your question correctly, e.g. figure 14.  The three main types of cone have different selectivities for any given wavelength of light, which translates into different voltage responses.
(note, also "fire" is not the usual term for cones, since they don't generate action potentials).
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How to find out colour strength in % from K/S value.
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Dear Dr. Roberto Daniel Lozano Sir,
Thank you for your answer and suggestion. 
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I am working on my own project and I am doing it in OpenCV python.
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I was wondering if some papers are published about some robust method of doing it.
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To assess the discolouration effect of food on elastomers, the colour must be assessed. One way is by the use of a spectrophotometer. But the latter only measures liquids or large objects. Does anyone have any information on that?
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Simply make the flash off and use the white lighting.There are several specifications to use the camera read them well. Through the histogram you can find out the lightness, redness and yellowness of your samples. when you do the lab parameter you should use the attached equations. This technique can be used for any material including foods and others.
Best regards
Aly
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I am able to calculate the CIE coordinates from the PL data ,now I want to calculate the CRI.Is there any relation between the CIE coordinate and CRI?
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Yes, it is possible and simpke: In the book (C. Oleari_Standard Colorimetry-Definitions,algorithms and software_Wiley 2016_ ISBN: 978-1-118-89444-6) all the alghorithms are given at pages 463-470. Moreover the free software attached to the book is downloadable from the Wiley website
Any comment is welcome
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How to remove high intensity pixels with the low intensity neighboring pixels in colored image using matlab?
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Dear Budhewar,
if you want to extract the gradient in color image, you can use the gradient of Di-zenzo (attached file).
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pls any one help to write the code of , masked image to color fundus image?
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Are you saying you want to only keep the portion of the color image that falls within the binary mask?
P.S. I will also get back to you with a recipe for exudate finding in fundus images with MIPAR (http://mipar.us)
Has anyone come across any research of association between colors and behaviors/moods?
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Any correlation between colors (visual stimuli) and behavior/mood (brain activity)?
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Here are major papers on color psychology. Elliot, A. J. (2015). Color and psychological functioning: A review of theoretical and empirical work. Frontiers in Psychology, 6, 368. Elliot, A. J., & Maier, M. A. (2014). Color psychology: effects of perceiving color on psychological functioning in humans. Annual Review of Psychology, 65, 95-120.
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I deposited the film using CBD ,but it's color does not change to yellow as expected.I changed the ratio of the chemicals but i got only white color not as supposed to be white to yellow color?
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The color of thin film is mainly due to the reflected light from the film. Pure CdS films are usually yellowish in color while pure ZnS films are usually light-white (depending on thickness). The alloy film Cd(1-x)Zn(x)S may vary in color depending upon the concentration of Cd and Zn in it. When x is close to 1, the film has more ZnS than CdS so the color may appear white. Similarly, when x is close to zero, the color could be yellowish.
Again, the color of the film depends upon the reflection spectra of the films which in turn depends upon the bandgap. If x=0.5, then technically the film must have equal amounts of Cd and Zn. At that pont, the bandgap of the material will be somewhere in-between that of CdS and ZnS. The color of the film will depend upon reflection spectra of the film at that bandgap.
I would suggest you to confirm the composition of the films by either EDAX or some other means. This would tell you whether the composition of the film is exactly same as what you expect from the composition of the precursors taken or not. You can also study the reflection spectra of the films and find the bandgap.
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Any test model I can use and reference?
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While i know of no studies involved, personal experience tells me that high-chroma (intensity) in the background is harder to read against by aging eyes --especially reversed-out type (that is white type on a color or black). Eyeglass coatings also come into play in that some displace certain spectra. From a high-contrast LED display, it appears that (in *my eyeglasses) red is displaced upwards and blue is displaced downward. Good Luck.
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.
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Hi Ahmed,
The CIE delta E calculations are quite simple, use the CIE76 formula on the following URL: http://en.wikipedia.org/wiki/Color_difference#CIE76
You'll also find the newer CIE94 and CIEDE2000 formulas there
Regards, Bela
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Like spliting a normal image into red, blue and green (RGB) images?
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I only partially agree with the previous answers. A color is defined by one specific wave length or a mixture of these wave lengths. There is a spectrum of colors that only consist of a single wave length, like a specific kind of Red, Blue, Yellow, Green, etc. Mixing these wave lengths at a specific ratio we get colors like White, Brown, and Pink. This is the physical view on colors.
However, our eyes have receptors for 3 different colors/wave lengths. The combination of the neural signal strength on these three receptors are interpreted by our brain as a specific color. Simply speaking our cone cells can receive Blue, Green, and Red light. If you see something that is pure Yellow, the Red and Green cones are stimulated. If you now stimulate the cones with the right combination of a pure Red and pure Green wave length your brain will also perceive this as Yellow. Your eye cannot tell the difference.
Based on this assumption how the eye works the previous answers are correct. This is why we use RGB for additive colors and CMYK for subtractive colors. This is just the natural result of how we perceive physics (through our eyes). The alternative would be to describe each color (when we want to store it) as a combination of an infinite number of wave length. This is not feasible at all. Why use an infinite number of values when 3 numbers in RGB will do the trick for our eyes?
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Snapshot Spectral Imaging for Color Measurements
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on top of the good answer from Juan Luis Nieves, i'll recommend (to reduce the main drawback) to use backside illuminated CMOS image sensor instead of CCD.
There are blue (NUV) sensitive and have faster readout.
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According to density of point distribution, we draw different color for the points, just like this figure does, which I saw from a paper. I wonder how to realize this? By some software? Or programming? Would you please help me if you know? Thank you !
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You can use the tool R (http://www.r-project.org) and the library ggplot2 (http://ggplot2.org).
Cheers,
Federica
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If microfossils are not fully coated, and only very few are showing colour change, can we consider it as re-worked? if only mineral grains are there how could we decide whether it is re-worked? what are the other signs of sediments re-working?
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Dear Archana,
You can try to observe the presence of sedimentary structures (lamination, isoorientation of the grains, erosional surfaces, etc.) to understand depositional environment and sedimentary processes. If you have microfossils, the presence of fragmented or abraded shells is an important sign of re-worked material. Another possibility to recognize re-worked sediments is to find microfossil associations with taxa referable to different ages.
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Dear colleagues, I received today in the lab the parasite from the image. The patient told me she has collected it from the narrow corners of her house from the bathroom, kitchen and there are many in many dark and humid places in the house. The images are performed  with the transmitted light microscope with 5x and 10x objective. Macroscopic aspect of the worm is 2-3 mm length light grey colored, cephalic end dark colored (almost black).The worm was very active in the container. The  patient also accused small bites (flea-like/bed bug-like bites) on the body (mostly on the arms and legs) and she told me that in the apartment from the upper level lives a family with dogs. The owners of the dogs have a low level of hygiene. She was afraid not to be some parasite from the dogs. I appreciate very much any help. Thank you all
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Dear Patricia, I agree with you Dear Rajib.
My best compliments..
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Sometime it's yellow and sometimes brown
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Yellow substances generally absorbs in the near UV - Violet region. So the yellow color do not arise from the absorption at their maxima, but from the band tails that extend toward the red.  The concentration (or the density in the solid) produces a shift in colour from yellow, orange, red, brown, etc. depending on how long the tail extends, due to the sensitivity of the eye which is maximum at green.  And  some times, small quantity of impurities (i.e. other oxidation states) that absorb in green can contribute to the brown colour of a substance that just absorb in violet-blue. 
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Based on colour in image we differentiate the features of earth. and I'd like to know which colour represents what. And I'd like to know for true color image, false color image.
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There is an explicit information regarding your question on this site: http://web.pdx.edu/~emch/ip1/bandcombinations.html
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I want to Know if somebody uses NCS (Natural Colour System) teaching in Latin america
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For many years now we've been using NCS in our colour courses for textile designers at SENAI/CETIQT. The students enjoy very much the exercises, in our classrooms we have complete student sets of NCS for every student. (We also teach Munsell and point out that the two systems are but different samplings of the same colour space).
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Usually yellowness appears in solar EVA sheets, after testing in DHT, but when I tried with PID EVAs, it turned into pink colour.
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For my understanding: Solar EVA sheets is "Solar Encapsulation film". An example I found in http://www.hanwha.de/sales-business/eva-sheet/. Is it correct?
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In the paper "Design Goals and solutions for display of hyperspectral images" by N.Jacobson, a method for enhancing CIE_1931 CMF beyond visible range is described but I am not sure how it can be implemented in MATLAB. 
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Thank you so much for your guidance. Currently I am looking for practical implementation of that idea. Can you provide me the supplementary material along with guidance? 
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My mid-polar to polar fractions have decomposed from a golden-brown colour to green, blue, violet and black colours, but I can still see the separation of compounds via TLC profiling. What could this be caused by, and what does it show? Help please
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Thank you. I was trying to understand why such occurs with the fractions instead in the crude. I think that it may also be due the 'absence' of other compounds (non-polar) to provide the 'stabilized' environment it was in iitially. Correct me if I'm wrong
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Chrominance Means and at the same how should we extract chrominance values from an image by using Matlab. If any one have any idea.
So please suggest for me regarding this and I will be very thank full to you all.
Are the purple red and indigo-like blu I recently obtained from Iris Germanica L. new?
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From Iris Germanica L. since the early Middle Ages, the extraction of yellow dye has been well documented along with use as colorant and for green lakes. However the technical coloring principles Iris Germanica L. contains do not seem to be well studied: only Mangiferin 209 (yellow - olive green) has been reported to date. Is somebody aware of other colors this plant produces? I recently obtained purple red and indigo-like blu (similar to its flowers). Have these colours been previously documented, as I am not aware of any mentions of this in the literature?
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As nobody from the 13+ millions of RG participants added comments to this question, I would like to precise that the disussed dye is a Cu-containing enzyme (cf. Plemenkov, V.V. Introduction into the chemistry of natural compounds (Bведение в химию природных соединений для химических, биологических и медицинских специальностей ВУЗов и университетов). Kazan (2001) Cu-containing enzymes: the Cu-ion stays at the base of the enzymes charged with redox-function (transport of O, of electron). This function Cu-enzymes often perform together with other redox-coenzymes (Fe enzymes, tetrahydropterin, and chinons) as reactions of this type are or with multielectron participation or represent transport of electrons long the molecular chain. Cu-sulfid enzymes are divided in a special group of cupredoxines characterized by their intense and variegated color. In medicine, they attract attention for their important role as electron transporters in fundamental processes like photosyntheses and breathing. In art techniques, thei were largely used since unrecorded times for organometallic dyes and green lakes, that with time may turn from green to red. Interesting proves of such cases in the decoration of Serbian baroque churches are reported by D. Korolija, Materiality and illusion. The colored transparent varnishes over silver foil in the Serbian Orthodox churches. History, technique and conservation (in Serbian). Novi Sad 2013.
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I am interested in any and all feedback related to measuring color value with mobile phone technologies. We have developed and tested an application that uses a single color reference (WhiBal card) to calibrate/generate RGB and Munsell values. When matched to known values via spectrophotometer readings, we have a lot of trouble in direct sun. We can accommodate some level of low precision, but would obviously like to get as close as we can to actual color. Anyone out there have experience with this?
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Adam,
Sorry to be late to the party, but are you still working on this? I am a color scientist and spent several years trying to get accurate color out of RGB cameras. As you already know, you need to control, the environment, ensure that the camera is giving you data that you can trust - they do all kinds of magic in the software, and are constantly adjusting stuff so you can get "point and click. Another roadblock is the fact that the spectral response of cameras is different from that of the eye. I have a blog post that explains that.
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I m interesting in color analyses and want to know how can I reach standards about colors? (particularly seafoods)
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I am not an expert and the fact is I don't know the answer of your question. But perhaps this article can help you: http://www.sciencedirect.com/science/article/pii/S0924224412001835
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I am studying the colour polymorphism of a crab spider and I want to know if birds can discriminate among the spider's colour morphs. I have calculated the excitation values of the four bird cone photoreceptors and transformed these into tetrahedral space coordinates (x, y, and z). I would like to represent these graphically in a colour tetrahedron, but i haven't been able to figure out how to obtain the coordinates for the vertices (representing the four classes of receptors: u/v, s, m, and l) of the tetrahedron. Any help will be much appreciated.
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I am not sure that I will be any help with this but I will have try because I am interested in the general idea of a tetrahedral colour space for birds and would like to ask a question at the end. I think you may have a very tricky problem! If you have transformed the values into x,y, and z co-ordinates presumably you can derive values for e.g. u/v=0, s=0, m=0, l=max. which would be an 'ideal vertex'. A possible set up for would be
u/v: x=1, y=0, z=0
s: x=-1, y=0, z=0
m: x=0, y=sqroot 2, z=1
l: x=0, y=sqroot 2, z=-1
However, although it is possible that pure u/v and pure l excitation can occur using light (rather than say electrodes) almost certainly no spectrum will give pure s or m excitation so the bird's colour space will be within the tetrahedron above but quite a lot smaller in two axes. How much smaller should be possible to work out from all the sensitivity curves but would I guess be a slog.
You might want to 'restretch' the reduced space to make it a tetrahedron again for display purposes and this could be considered legitimate since there is no 'metric' to subjective colour. Whether it would be worth the effort of recalibrating all your values I don't know. You might want a dedicated programme to calculate all that!
My next thought is that presumably the birds could tell the spiders apart on the basis of shade as well as hue, in which case don't you need a four dimensional space anyway? As I understand it a tetrahedral space will only cover the hues, all normalised for relative intensity? The human ability to distinguish by colour would I think be based on a three dimensional space.
And finally my question is whether we know that birds actually use their four receptors to generate a four dimensional hue/shade space, as the receptors would theoretically allow them. Is it possible that the pathways that extract hue and shade 'throw away' a dimension and just construct a triangular space like ours, but spanning a wider range up to UV? Since the bird's brain is so much smaller than ours it may not have space for analysing in four dimensions and may simply use the increased number of receptors as a short cut to getting more colours with less processing. They might even use the four receptors to create a linear hue sequence using a system of analysis closer to the cochlear, where pitch is assigned to wherever maximum excitation is. OK, we perceive harmonies, but most of us are not that good at discriminating them. I don't know the literature here so may be way off tack but I would love to know if this has been established somehow.
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I am trying to write a simple program which should take a normal image and convert its colors to the similar colors that a specific bird can see. The only interest here is the color, the way a bird (like european starling) can see them, not the perception which is made in the animals brain. Basically the question is, what will we see if we take a bird eyes?
I want to use this comparision http://www.webexhibits.org/causesofcolor/images/content/Absorption_peaks.jpg to write a mapping program. Could anybody suggest me how to find a mapping function using that?
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Is this actually a solvable problem ?? You are going from 3 to 4 channels. The information of the 4th channel is nowhere in your RGB ( only in assumptions about source materials ). This means to me that the only "new" information you get is something you yourself just added implicitly.
To me, this problem is close to: can I create a color a human sees from the 2color signal most other mammals have.
Or, at the extreme end: how do I get a color image from a b&w image.
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Is there a way to convert color specifications defined by N.B.S. units in x, y, Y color space under illuminant C, 2° Standard Observer to delta E* values in CIE L*a*b* color space under D65, 10° Standard Observer? I have been unable to find a mathematical conversion due to the difference in illuminant and Standard Observer function.
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I would venture a guess and say no. The two specifications are done with different spectral content and responsivity and it does not sound like you have any spectral information available. However, I would suggest following Aleksei Guzev and calculate the response of relevant materials from their spectral reflectance, using both specifications. Perhaps this will show you some pattern or relation between the two specification that work for the materials you work with.
Regards
Anders
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As a function of time, the surface of silver becomes covered by a granular layer of black coloured Ag2S grains. The thickness of this layers increases with time. During this process, the colour of the surface changes gradually. In the early stage of corrosion, silver becomes yellowish and only in a later stage it becomes black. It is said the colour changes with the thickness of the film formed. Once the thickness of the film is larger than the wavelenght of visible light, the colour of the pigments becomes dominant.
The yellow colour is considered as an interference colour. But how can the colour be the the same from all angles at which you look at it. Iridescence is supposed to give different colours at different angles and result in "rainbow colours".
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Iridescence also depends on the film thickness. It is optimal for films thinner than 500 nm (for interference effects in visible light). Thin tarnish layers on silver can vary from yellow to red to blue before the layer becomes black, its final colour. The attached photograph shows red and blue interference colours on the outer edges of a silver object (Photograph courtesy of Margo Brunn, Provincial Museum of Alberta).
For thicker tarnish layers, the rainbow effect (caused by iridescence) gradually vanishes.
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I am looking for a way to quantify "visual capacity".
In our paper (http://www.frontiersin.org/psychopathology/10.3389/fpsyg.2013.00352/abstract), we define visual capacity as a conglomeration of the following visual skills:
visual acuity, visual sensitivity to light (contrast sensitivity), motion sensitivity, color sensitivity, visual field size, binocularity & stereoscopic vision?
My questions concerning this matter are:
1) Is this an exhaustive list - probably not - but what is missing?
2) How can one effectively (fast, easy, cheap) measure the following constructs in a given individual:
2a) visual acuity?
2b) visual sensitivity to light (contrast sensitivity)?
2c) motion sensitivity?
2d) color sensitivity?
2e) visual field size?
2f) binocularity?
2g) stereoscopic vision?
3) Is there already some research on what constitutes "very good vision"?
Thank you for your support!
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I think your local Orthoptic department would be able to assess all that you have described. It’s an interesting question & I will be intrigued to see what people think. My thoughts are that each component has it's own tests with normative values, i've not come across a 'visual capacity score' as yet:
1. Visual Acuity: the present gold standard is considered the crowded LogMAR chart (EDTRS)
2. Contrast Sensitivity: the Pelli-Robson chart is quick and easy.
3. Colour vision: Ishihara is commonly used; however there are lots of options including the 100 hue test of which there is a free version online: http://www.xrite.com/online-color-test-challenge
4. Visual field: The Goldmann Perimeter or the Octopus 900 are considered the most accurate (these are kinetic visual field analysers – moving target)
5. Binocular single vision (BSV):
1 Sensory Fusion (bagolini glasses/worth lights)
2 Motor Fusion (Prism fusion range)
3 Steropsis (Frisby stereoacuity test)
6. You could also consider ocular motility? Recording a field of BSV, and quantifying this using the Woodruff scale?
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Correction of cataracts in relation to the true colors - color recognition.
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There are quite a few:
Intraindividual comparison of color contrast sensitivity in patients with clear and blue-light-filtering intraocular lenses. Schmidinger G, Menapace R, Pieh S. J Cataract Refract Surg. 2008 May;34(5):769-73. doi: 10.1016/j.jcrs.2007.12.034.
Color discrimination by patients with different types of light-filtering intraocular lenses. Ao M, Chen X, Huang C, Li X, Hou Z, Chen X, Zhang C, Wang W. J Cataract Refract Surg. 2010 Mar;36(3):389-95. doi: 10.1016/j.jcrs.2009.09.038.
Intraindividual comparison of color perception and contrast sensitivity with and without a blue light-filtering intraocular lens. Eberhard R, Roberti P, Prünte C. Eur J Ophthalmol. 2009 Mar-Apr;19(2):235-9.
Color perception with AcrySof natural and AcrySof single-piece intraocular lenses under photopic and mesopic conditions. Cionni RJ, Tsai JH. J Cataract Refract Surg. 2006 Feb;32(2):236-42.
Blue-light filtering intraocular lens in patients with diabetes: contrast sensitivity and chromatic discrimination. Rodríguez-Galietero A, Montés-Micó R, Muñoz G, Albarrán-Diego C. J Cataract Refract Surg. 2005 Nov;31(11):2088-92.
Effect of a yellow intraocular lens on scotopic vision, glare disability, and blue color perception. Muftuoglu O, Karel F, Duman R. J Cataract Refract Surg. 2007 Apr;33(4):658-66.
Comparison of contrast sensitivity and color discrimination after clear and yellow intraocular lens implantation. Rodríguez-Galietero A, Montés-Micó R, Muñoz G, Albarrán-Diego C. J Cataract Refract Surg. 2005 Sep;31(9):1736-40.
Comparison of color perception after tinted blue light-filtering and clear ultraviolet-filtering intraocular lens implantation. Khokhar SK, Jindal A, Agarwal T, Panda A. J Cataract Refract Surg. 2011 Sep;37(9):1598-604. doi: 10.1016/j.jcrs.2011.03.044. Epub 2011 Jul 12
just to name a few...
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I have colour image. I want to segment the image using depth information ?
Is it possible ?
What are the approaches ? Any links , Docs ?
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I would like to recommend you one of the most state-of-the-art research group working on RGB-D image segmentation:
In this page, you can find many papers related to image segmentation. I recommend you first check the following paper:
This paper presents a state-of-the-art method of RGB-D image segmentation. For more basic knowledge and/or simpler solutions, please check the related work section of this paper.
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I am using Ocean optics spectrometer having USB2000+ detector with LS-1 tungsten-Halogen lamp. While doing color measurements, we have to choose observer (2-degree/10-degree) and illuminant (D50, D55 etc.). What is the basis of choosing the observer? Is the illuminant code is based on the lamp color temperature? How can I get the code for the lamp? I am using LS-1   having color temperature 3100K. Can we do color measurements in both transmission and reflectance mode i. e. on glass and metal?
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For the analysis of soil organic carbon by WB method,I have used 1 g soil with 10 ml of 0.1667M K2Cr2O7 solution, 20 ml concentrated H2SO4,200 ml water for dilution,10 ml H3PO4,10 ml of NaF solution,diphenylamine as an indicator,0.5M FeSO4 solution as a titrant.
During dilution,different soil sample shows a variation in colour i.e. some are orange and some are dark green,but with the same end point of light greenish colour after titration.Why is this colour variation takes place in different soil samples,Is this not an appropriate procedure for soil organic carbon?
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1)Transfer 1 g air dried soil into a 500ml conical flask.
2) Add 10 ml 1N K2Cr2O7 solution and  20 ml concentrated H2SO4.
3) Swirl the content of the flask 2 or 3 times and allow the flask to stand for 30min. for the reaction to complete.
4) Add 200ml distilled water to the flask to dilute the suspension.
5 ) Add 10ml of orthophosphoric acid or 0.5gof NaF and 1ml of diphenylamine indicator. A deep violet color will appear.
6) Titrate it with 0.5N ferrous ammonium sulphate till the color changes from violet to blue and finally bright green.
7) Note the vol. of the ferrous ammonium sulphate used in titration.
8) Carry out a blank titration (without soil), the same way.
Calculations-
Organic carbon% in soil=(X-Y)ml× 0.003 × 100 ÷ 2×W=Z
Organic carbon% in soil= Z×1.3= R
Where, X= blank titration reading.
Y= sample reading,  W= Weight of soil used
* Assume that organic matter contains 58% carbon, thus the organic matter content of the soil will be calculated as -
Organic matter in soil (%) = R × 1.724
 
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I am planing to use a Jaz spectrometer to measure the flower color. I have installed the oceanview software. But as there is no manual for the software I am having a hard time to figure out the procedure. Can anyone help me?
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Have you looked at the manual available on the net?
However, you need more equipment than just a spectrometer for instance a light source, and a reference white and a reference black for calibration.
Regards 
Anders
What is the application of geobotany in the Manganese deposits exploration?
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I'm interested in the exploration of manganese in Iran, (in Urmia-dokhtar Magmatic arc). Which particular species grows? What is the effect of the manganese on plants?  Change the color of the plants? The lighter colors spread? Plants are changed in size?
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Manganese is essential for many fundamental plant processes and any search site should find plenty of material on the symptoms of Mn deficiency as well as about your other queries. The issue in this case is likely to be manganese excess or toxicity and here again the web will help. For example http://www.ncbi.nlm.nih.gov/pmc/articles/PMC34824/ . If the mineral deposits are superficial and chemically accessible to local plants, these are likely to have adapted. Environmentally, mining is often a nasty business and if you/Iran are concerned about mitigating the consequences on vegetation of leachate from tailings, raising pH will make the metal less available to roots. http://www.ncbi.nlm.nih.gov/pubmed/23124167 may also be of interest. Finally, you might want to consider bioremediation in which certain plants actually extract toxins from soil. I hope some of this helps.
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5 answers
I have attached an example image to show the problem: This is mosaicking process for different month HR data using Erdas software. I had followed different steps for mosaicking but I am unable to solve this color correction. I would like some suggestions regarding this error.
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Hi SK,
Data type 8-bit. When I was using histogram matching result came more different. I am using the data for same area from different time periods. But this error our team solved using PCI geomedia. But I am trying to solve this problem using ERDAS imagine.
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2 answers
I focus on extracting FVC by some other color space. does anyone introduce other ways or provide some good advise.
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Hi Li,
FVC is a rather ill-defined property to start with, as it is highly dependent on the scale of the system being monitored, the spatial resolution of the measuring instrument, as well as various aspects of the observation protocol. In addition, if you don't know and specify what range of errors is acceptable in your situation, then any answer will be acceptable. So, in the absence of such information, I'd suggest the answer is 42, following the method of Deep Thought!
Joke aside, please provide some background information on the nature, scope and purpose of your project, why you want to estimate FVC, what environment you are looking at, etc. The tools and methods should be selected only after your objectives are clear, including the maximum tolerable level of uncertainty.
Good luck! Michel.
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I am pursuing my PhD and preparing the material for a white light source. I am getting the PL results as required for a white light, but not able to calculate the CRI(Color rendering Index).
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There are several ways of calculating CRI Ra. You can perform calculations by hand, using spreadsheets or computer programs (e.g. Matlab, Phython).
If you alrready measured the spectral power distribution of the light source, and have them in tabular form, you can simply insert them in a spreadsheet which performs CRI calculations. For example, there is one available on the net: bramley.auld.me.uk/406/Calculating%20CRI-CAM02UCS-v2.xls You can plug in your light source spectrum and it gives you the CRI Ra, as well as CRI special colour rendering index for 14 samples, light source CCT and CRI-CAM02UCS.
What is the best classification application in order to achieve the accuracy result?
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180 answers
Hi, I want to classify pottery fragments, so I have color and texture features for 50 Images this means I have 50 vectors for classification. What is the best classification apply in order to achieve the accuracy result?... Thanks so much.
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Dear Nada, (A) There is no consensus on accepted or correct methodology and no consensus as to accepted or correct methods (Rudman, 1998). Rudman, J. (1998). The State of Authorship Attribution Studies: Some Problems and Solutions. Computers and the Humanities, 31, 351-365.‏ (B) According to my experience and knowledge the best classifiers are: Parallel Random Forest Random Forest (with at least 100 trees) LIbSvm (in many times it's better than SMO) Logistic regression (LR) Multilayer Perceptron (MLP) C5 or J48 (an improved variant of the C4.5 decision tree induction (Quinlan, 1993)) BayesNet (BN) AdaBoost (C) The following paper Fernández-Delgado, M., Cernadas, E., Barro, S., & Amorim, D. (2014). Do we need hundreds of classifiers to solve real world classification problems?. The Journal of Machine Learning Research, 15(1), 3133-3181.‏ evaluated 179 classifiers arising from 17 families on 121 data sets. The best results were achieved by The parallel random forest ( implemented in R with caret) The random forest in R and tuned with caret was slightly worse The LibSVM implementation of SVM in C with Gaussian kernel Six RFs and ve SVMs are included among the 20 best classifiers, which are the bests families. Other classifiers with good results are the extreme learning machine with Gaussian kernel, the C5.0 decision tree and the multi-layer perceptron. Best regards, Yaakov
What are the advantages and the disadvantages of HSL,HSV and RGB ?
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40 answers
In image processing and computer graphic, there are many coloring modes and models to represent the colors of the image. 1- HSL (hue-saturation-lightness) 2- HSV (hue-saturation-value) 3- RGB (Red, Green, Blue) What are the advantages and the disadvantages of those three modes? and in which case it is better to use in your opinion ?
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The three models are all equivalent. So, there are no real advantages or disadvantages of any of these models. There are only minor differences. First of all, the RGB model is exactly how our hardware (cameras and displays) work. This makes this model a little bit more suitable for interfacing with these devices. The HSL/HSI models borrow a little bit from human perception, but are finally only transformations of RGB. Due to their cylindrical shape it is easier to interpolate between colors in HSL/HSI space compared to RGB. Note that HSL/HSI only provide better intuition for humans, but they do not actually replicate human perception. They have the exact same deficiencies as the RGB model. E.g. these models allow for a resolution of red values which is not perceivable to the human eyes. For green and blue, however, humans might perceive steps in the colors (this depends on the number of bits used per color channel). You should read up on Wikipedia (http://en.wikipedia.org/wiki/HSL_and_HSV) about the relation between HSL/HSI and RGB and how they do not map well to human perception. Use RGB when you print things to the screen, HSV when you provide a color picker to the user. If color perception is really your concern don't use any of these. Instead use something like CIELAB.
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As I know, there is a good paper talking about this, B. R. Bennett, 'Spectra of Quantized Signal' 1948. 
I am wondering there is newer report on this topic for the signal with colored spectrum? Thanks,
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Dear friend
You can see the attached paper . I hope to help you
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2 answers
I want to make electronic ink in electrophoretic displays.
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thank you very much
What statistical analysis should I use to demonstrate the power of charge-ability of particles?
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4 answers
Hi reader,
I'm looking for a compound, which can be added to agar medium, that changes colour or makes an oxygen gradient clear in any other way. Preferentially the added chemical should be non toxic and easy to apply. Does anyone know of such compound?
Many thanks in advance!
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The first thing that comes to mind is Resazurin, which changes color with the presence/absence of Oxygen. But if you are using agar medium, it will be exposed to room air/O2 unless you seal it somehow. But maybe there's a better compound out there for you. Hope this helps. 
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12 answers
If the color of the brace (drawings, stickers, paintings) is important in brace treatment (idiopathic scoliosis)?
Is more likely to be used from the usual white brace? Does anybody have experience with this subject?
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Dear Dr. Korbel,
The children prefer colored braces. In my opinion this kind of braces increases the compliance and duration of brace wearing through daytime. Especially, in little children. 
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5 answers
what is origin of color generation from nanoparticles and nanostructures?
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For nanoparticles, it's due to surface plasmon resonance mainly dependant of the dielectric constant of the material of the nanoparticle and its diamater. For instance, see:
and
For nanostructures, it depends of the structure (bumps, grids, 2D, 3D, ...), but for a periodic structures, as photonic crystals ,you have photonic bandgap as electron bandgap for semiconductors but for photons. As instance, take a look at:
You can see these natural effects of color of photonic crystals on some butterfly wings.
Kind Regards 
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60 answers
.
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An expanded response follows from Scott's earlier answer. Think of graphene’s π system (emanating from each carbon’s 2pz atomic orbital) that extends in two dimensions. This extended conjugation over which electron density is delocalized on both sides of the graphene sheet accounts for the lowest energy optical absorption, from the far IR to the UV, and is a so called zero band gap band; transitions are intra-band. When a carbon atom is oxidized, whether by formation of a carbonyl, hydroxyl, glycidyl ether, carboxyl group, or other process, the conjugation involving that carbon atom is cut. As this cutting (oxidation) progresses, the most lengthy paths of delocalization are shortened, and a band gap opens in the longer wavelength region of the IR-visible. This gap progresses to shorter wavelengths with increasing oxidation. The lowest unoccupied π-based excited states, as the most lengthy delocalization distances become shorter and shorter, increase in energy, turning GO from black to brown to yellow-brown to yellow, as oxidation progresses. A review of experiments on the visible-UV spectrum of graphene may be found in my recent paper, Curr. Opinion in Colloid and Interface Science, 2014, 19:163-174.
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3 answers
I would like to convert dye color which is absorbed at say 400 nm max, into Pl-Co index. Any suggestion for it.
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Michal Vik Thanks for your answers.
Do you have an idea about how Cx and Cz are determined?
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5 answers
Spiro OMeTAD solution made for Perovskite solar cells are turning red in color when taken inside a glove box or when they are stirred excessively. Can anyone please let me know the mechanism involved?
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When Spiro-OMeTAD is dissolved, it has whitish color. After adding very small amounts of dopants (LiTFSI and tBP), the color usually turns yellowish. Please check the amounts of dopants.
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5 answers
Seed color is associated with preharvest sprout (PHS) tolerance, thus, for areas with PHS problems, this information might be useful.
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Khaled, the second paragraph is what I wanted to find. Though determining degree of colors (intensity maybe) is also a great idea.
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8 answers
i have deposited TiO2 with pulse laser deposition system at room temperature and 10 e -6 pressure infact thin film was fabricated but the target has changed colour from white to steel grey where laser was incident.Can anyone suggest the reason for it? the laser wavelength was 532. 
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Most oxide targets unless they are very dense, l would always change color from light brown to dark brown with repeated ablation. It is unavoidable, as stated in earlier answers, they become reduced. therefore one removes the target scrapes it after a few ablation runs, and then sticks thetarget bck again, and tries to deposit a film with a fresh target surface.
 this is a typical problem faced while sputtering with oxide targets also, and the problems are similar to pulsed laser ablation.
K. Sreenivas
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5 answers
I am getting yellowish color during the synthesis of plasticizer, which is developing because of long reaction time and higher reaction temperature. 
I have tried convention methods like charcoal, bleaching earth, zeolites but didn't solve the problem.
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Dear all;
for general purposes in a chemical lab, the discoloration of the product is eliminated by passing through silica or alumina columns, other methods such as extraction and distillation also works. I don't known if you have tried any of these conventional methods. Regards
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7 answers
Anyone has experience on the anoxic tank, please let me know. Thank you very much.
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It will depend on the waste being treated.  For traditional wastewater, the sludge will be darker than an AS tank
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1 answer
I deprotected my fmoc-amino acid for further coupling. Upon analyzing it after kaiser test, I got two different coloured beads, dark blue and orange together. What can be the reason behind this and the solution for this problem?
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Hi,
it depends on what you call "orange". If it is a shade of pale brownish red, this may be related to secondary amines, as the Kaiser test is known to detect both primary amines (blue) and secondary amines (brown). Unfortunately I am a color scientist and not a chemist, so I can't help with the solution of the "problem" (if it is one...).Let me know if it helped... Regards, Olivier
How do you remove the colour difference between two tiles of LISS-III images?
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3 answers
The mosaic image of LISS-III images of two different tiles (paths) causes the difference in the colour. How do you remove this colour difference? 
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Have a look at: http://vision.ece.ucsb.edu/registration/mosaic/ C. Sun, R. Beare, V. Hilsenstein, and P.T. Jackway, Mosaicing of Microscope Images with Global Geometric and Radiometric Corrections. Journal of Microscopy, 224(2):158-165, November 2006. ( http://vision-cdc.csiro.au/changs/doc/sun-etal06jmi.pdf )
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6 answers
After acetolysis some pollen are small and transparent. I'm searching for some color if it's possible to color it.
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You can also use fuchsin instead of safranin.
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6 answers
I want to find a colored filter glass that combined from a low- and high-pass filter to support 780 nm wavelength by 10 or 15 nm accuracy in peak of transition.
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Dear Sajjad,
If you would be more precise in telling us the purpose of your desired filter, we could probably be of more help. It seems that you do not want to clean the output of a 780 nm laser. If you want to filter out a spectral region around 780 nm with  about 30 nm FWHM then you may think in using a combination of a shortpass edge and a longpass edge filter, e.g.:
Shortpass (SP):
Longpass (LP):
Filter curves:
for LP see:
for SP see:
With this combination you may reach about 25 nm FWHM due to:
Rejection wavelength: LP: 590-740 nm; SP: 850-1050 nm
Transmission wavelength: LP: 805-2000 nm; SP: 400-775 nm
Cutoff wavelength: LP: 775 nm; SP: 800 nm
As attached file you can see the result (transmission curve, dotted red line) if both filters are used together (I have approximately overlapped the two curves in the region of interest). The transmission region is not ideal, however, the transmission region on the lower wavelength side can be changed slightly by tuning the angle of the filter from 90 degrees incidence to lower values - by this you may obtain an ideal filter for your purpose with about 30 nm FWHM.
Both filters are quite cheap: 90$ each, so the combination is 180$ only.
Hope, this information helps you.
Regards
Wolfgang Kiefer
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I'm currently working on a project, where colour is measured during the storage life of apples. When using, Yxy system, can we compare x and y values separately and statistically analyze them separate as different parameters?
Is it OK to do that? 
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Sakalya,
I agree with Huw Owens.  The CIELAB system would be preferable, although your measurements can be in any of the convertible units.  Most instruments can be set to give you results in CIE L*a*b*, which eliminates the need for mathematically converting from other units, reducing errors.  Your main concern will be keeping the color instrument calibrated.