MATLAB: Please, give some advice on law of signal/noise propagation in image processing

Question

Is is possible to determine experimentally how signal and noise change when one adds two or more images together (gray scale frames). I have many frames of the same scene and I need to determine the law. Thank you.

Answer 1

For one image the std dev is zero. Then calc the std dev for two images for every pixel, and take the mean to get the mean std dev for the entire image. Note this value. Repeat as you add more and more noisy images. For constant noise statistics, the std dev should go down by the square root of the number of images. So 8 images have half the noise of 2 images, because 8 is 4 times 2 and sqrt(4) = 2.