RGB range for an image

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.

Answer 1

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

ok Sir...If I have developed an algorithm for a video taken from lets say blackberry and I want that it should also work for the video taken from digital camera and the working of algorithm is based on RGB values. Then what should I do so that the RGB range of both the videos taken from different cameras becomes the same. Is it possible to achieve this or should I change my algorithm. Because I have used different algorithms like gamma correction,power law formula etc. but still the range of RGB is different for both videos. Is there any standard method of doing it. Thanx

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.

Are there any effective color calibration techniques in matlab.

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).

Answer 2

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