Steve
I still disagree, as I suspect you are confusing signal noise ratio with noise on its own.
Total noise in an image (not just shot noise) is not by definition always smaller than the signal, and cannot always be fully calibrated out.
Very dim objects can have a signal well below the noise floor of the camera, and no amount of quadratic summing will make the signal appear.
Adding identically exposed images will increase the *S/N ratio* by the square root of the number of images. But if the S/N ratio is close to 1:1
...which is what I alluded to earlier...then you'll still end up with a noisy image.
Quote:
Originally Posted by skwinty
the noise is by definition substantially smaller than the signal over the integration time.
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