Quote:In film photography, we never did worry about this, we just used the Rayleigh criterion, which essentially uses green light with a wavelength of 5120 Angstrom or 512 nm. Green light was chosen because that is what the human eye is very sensitive to.The Ratleigh criterion does not use a specific focal length. The angular resolution of an optical system can be estimated from any wavelength of light and the diameter of the apparent aperture.
It does indeed make a difference when pixelpeeping, as visible light ranges roughly from 390 to 700 nm, although you could argue it goes from 380 to 750 nm. That is approximately a doubling of wavelength, and halving of resolution, roughly speaking.
It will still resolve enough at 400 mm, I can assure you, because the resolution of teh sensor does not actually change, it is the total system resolution that changes because the diffraction limits changes. However, the better a lens is, the closer it gets to the diffraction limit, and certainly at the smaller apertures almost all lenses will be diffraction limited.
Do also note that MP limits as discussed are really system MP limits, based on resolution at specific apertures for a lens and sensor system.
I'll see if I can work out a few examples to show you what I mean. However, that has to wait till the weekend - away from home for work currently, and limited in what I can do as a result.
Kind regards, Wim
In your former example, you used a blue light source diffraction table, not green.
However, in photography we usually use white light.