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RGB range for an image

Asked by Beenish Mazhar on 15 Feb 2013

Does the R,G,B range varies for the image taken with different cameras. Suppose I capture an image with blackberry and I capture the same image with a digital camera; would the RGB range vary for the image in both scenarios or would it be the same.

0 Comments

Beenish Mazhar

2 Answers

Answer by Image Analyst on 15 Feb 2013
Accepted answer

Of course it does. Different cameras have different spectral responisivities, different exposures, different gammas, different algorithms they apply to "improve" the image for you, etc. Don't think that if you take a photo of, say, the x-rite Color Checker Chart (a standard color calibration target), that you will get the nominal sRGB values out. You most certainly will not. Not from your camera or any other camera. You'd need to do a color calibration to post process the image if the sRGB image is what you wanted because all cameras are different.

Additional Training:

http://www.cis.rit.edu/mcsl/SSC

x-rite

http://www.drycreekphoto.com/index.html

http://www.poynton.com/

http://www.cambridgeincolour.com/tutorials.htm

http://www.dpreview.com/articles

4 Comments

Image Analyst on 15 Feb 2013

You either have to have an algorithm that is robust enough to handle different color gamuts and still get the main job done, or you have to calibrate your system by having a known color calibration target in your scene. For example, if I have to find a red spot on a green background, I can probably do a pretty good job of that despite the fact that the image doesn't have exactly the same colors from every camera.

Beenish Mazhar on 15 Feb 2013

Are there any effective color calibration techniques in matlab.

Image Analyst on 15 Feb 2013

No, nothing built in. You have to know what to do (for example cross channel polynomial regression between desired RGB and actual RGB), and do the steps yourself (for example, with polyfit).

Image Analyst
Answer by Walter Roberson on 15 Feb 2013

The sensitivity of different devices varies. And their gammas will possibly differ.

This starts getting into color theory. You can start to see the complexities if you read about a standard designed to work around these problems, http://en.wikipedia.org/wiki/SRGB#The_sRGB_gamut

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Walter Roberson

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