Hi all, I am using a (Allied vision tech Pike)CCD camera to take some images of diffraction orders in far field. Since I did not find any calibration curve from the manufacturer, i decided to do my own calibration. I basically kept gain constant and varied the shutter value in its entire range. then I repeated this for several gain values. I recorded the image for each measurement as the total intensity by summing the intensity of all pixels using a matlab code. I get the curve as attached http://dl.dropbox.com/u/52559364/Picture1.tif [Broken]. I derived a set of equations using basic fitting which define these curves in terms of gain, shutter and intensity values. relative_gain = gain/200; coeff = 0.57*(relative_gain^2) - 0.44*relative_gain + 0.87; Intensity = coeff*((7.4e+5)*shutter + 6.2e+8); (I derived these equations wrt to a gain of 200. So i divide each gain value by 200 to get relative gain) Now the problem is : when i take various images at different shutter and gain value, how do i normalize them? i.e. compensate for the different gain-shutter value for each measurement. Do i just need to divide the images with the total intensity calculated? For example i take an image with shutter-gain of 3300-200 and another with 100-10. How can I compare the total intensities of these two images? I am really stuck. Any help will be appreciated.