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I have a very simple question that arises in a photo forum in Brazil.

Some guy put a formula to calculate the maximum resolution possible in a camera lens based on their aperture. The formula is 1800/N = (maximum resolution in lpmm)

Were 1800 é a constant and N is the F stop of the camera.

This means that any lens in F 22 will have the maximum resolution of 1800/22= 81.8lpmm.

By looking at this formula I think to myself that they can’t be real because the diffraction that will limit the maximum resolution is in a function were the wavelength of light and the real aperture size are needed to calculation, since the wavelength have a real physical value and lens aperture F stop don’t.

Based on this formulae a 5mm focal length lens in F22 that have a real aperture of 0.23mm will have the same maximum resolution that a 2000mm lens in F22 that have a 9cm aperture real diameter.

This can be correct?

They claim to have a factor were the focal distance will influence on the diffraction, making a 0,23mm hole have the same effect on light that a 9cm hole.

Can you help me and point were are the right or wrong of this assumptions.

Thanks in advance,

Alex

Sorry if the question is to simple.

PS-I really work on wikipedia to make sense on this formula but can't find anything.