I got into more specifics because I was interested in more than just digital resolution.

Photographic System Resolution explains the relationship between digital resolution and lens sharpness and it also addresses the challenge of comparable sharpness with different film formats and scanning vs. wet printing.

DxOMark tries to link lens sharpness and sensor resolution with their Perceptual Megapixel (PM) resolutions for lenses on difference sensors.

The formulas for system resolution and PM necessarily assume that the resolution is consistent across the entire image. But lens sharpness varies the further you go from the center of the image circle. It's much more complicated than most people need to know.

I got into more specifics because I was interested in more than just digital resolution.

Photographic System Resolution explains the relationship between digital resolution and lens sharpness and it also addresses the challenge of comparable sharpness with different film formats and scanning vs. wet printing.

DxOMark tries to link lens sharpness and sensor resolution with their Perceptual Megapixel (PM) resolutions for lenses on difference sensors.

The formulas for system resolution and PM necessarily assume that the resolution is consistent across the entire image. But lens sharpness varies the further you go from the center of the image circle. It's much more complicated than most people need to know.