Contrary to conventional wisdom, higher resolution actually compensates for noise

The argument above provides a method to compare cameras with different resolutions. A high-resolution camera can still be turned into a low-resolution camera by averaging its pixels.

In order to compare all cameras and not just pairs, a reference resolution can be chosen and equivalent SNRs at this resolution are computed. Let N_ref denote this reference resolution. Consider a camera with N Mpix. To obtain an image with N_ref pixels, N / N_ref pixels need to be averaged out to produce a single pixel in the output image, so the noise decreases by a factor of . We then deduce that SNR_ref at resolution N_ref can be obtained from the nominal SNR (in dB) using the formula

Notice that if the reference resolution N_ref is very large, or if the initial sensor has a low resolution, the normalized SNR can actually be lower than the nominal SNR.