How to calculate visible resolution limits

Bob Wheeler implied that there should be some minimal requirements for enlargements being made from LF and MF equipment (at least this is what I think he was implying). We can calculate these requirements as follows:

{line/mm eye resolves} x {neg/trans enlargement factor} = {minimum l/mm required to fully resolve what the eye can perceive on final print}

This will give a good starting reference for establishing the minimal system resolution requirements. Indirectly, one can use this to determine if their photo system is capable of delivering the desired resolution.

If we assume full frame enlargements (no cropping), a tripod is used in all cases (to eliminate shake from the system), a 'good' enlarging system (no loss of resolution from neg/trans to print), and the fact 'young' human eyes are reported to be able to resolve 7 lines/mm, the following can be assumed:

For 4x5 negatives and transparencies:

For 6x6 negatives and transparencies:

For 6x7 negatives and transparencies:

Several things become immediately apparent: