I hope I am not in the wrong place to ask this kind of question since it is more about image acquisition than photography.
I have to use a Microsoft Lifecam HD webcam to take snapshots of a laser beam and measure its relative intensity. This means that I do not need to compare it to any standard measurement, I just want a behavior that is as close as possible to linearity, that is, if I take two pictures of two different beams and one is twice as powerful than the other, I should be able to measure this 2x factor in the images. It is important to note that the frequency of the incoming light is always (approximately) the same, therefore I should not need to worry about different sensitivities at different frequencies since there are no different frequencies. I have no interest in chromatic fidelity, I only care about intensity. I think I can measure image intensity by simply summing the RGB values from each pixel.
I wonder how to set the camera so that I can obtain a close to linear relation between the image intensity I can measure from the saved image and the actual incoming light intensity. I have access to the following properties:
- White Balance
- Saturation (remember that I do not care about color, the light I am observing is nominally monochromatic at 632 nm, which is close to red)
Of course these settings have to stay the same between comparable images, what I am asking is whether there are specific values I should keep on all my snapshots to obtain linearity. For example: should I desaturate the image or does that change the intensity (measured as R+G+B) in a nonlinear way? Should I choose a different method to measure image intensity?