Obtaining the variance of the image noise I am implementing a digital image correlation algorithm, and I found that for some calculations the variance of the image noise would be very interesting. 

How can I determine that parameter? The only thing I have are a set of 1000 images of a metal deformation process and no prior information about the noise in the image.
I found the answer. 

The correct approach is the next one:

In a controlled environment (appropiate ligth, no vibrations,...) take several images of the same object (e.g. a white sheet of paper). 
Then calculate the variance of each pixel on time (in different images).

Finally mean all those variances and there it is! the variance of the image noise.