A while back, Danny B started a thread on difference in resolution between LF an d MF. Pat Chase stated that good human vision can only detect about 7 lpmm of r esolution, anything less would be viewed as blurred, or poorly focused. Anythin g greater would be perceived as sharp. (He has a great deal of experience in t his area) Assuming great LF lenses can only deliver on 56 lpmm to film, when en larged, assuming no losses in the process, a 3x enlargement would yield on paper  7 lpmm. Therefore a 4x5 chrome enlarged only to 12x15 viewed up close, sa y 1 foot, would be the max. enlargement this print can withstand before it appea rs to be blurred or poorly foccussed. I realize a prints viewing distance shou ld be equal to the diagonal of the print. But thats not usually the case, spec ially with LF shots, everyone wants to inspect the detail up close! So for this example, I am considering how much scrutiny a print can handle up close.

After viewing Chris Perezs LF lens tests (thank you Chris for sharing this ver y useful information with us) linked to this home page, it is clear that many le nses deliver poorly on the edges or sometimes even in the center at certain f st ops. If the lens delivers only 30 lpmm to the edges, hence the weak link in the chrome, which now allows for only 2x enlargement max. before it becomes perceiv ed as not sharp. Is this math correct, or is there some other missing factor? Could this explain the erratic behavior LF sometimes delivers on 4x5? We could very well be experiencing very low LPMM due to shooting at a poor resolving f s top on the lens, using poor optics, poor focus, etc. Any one of these variables can produce much poorer results then we would expect in LF, specially 4x5, 8x10 is much less prone due to the same resolution at 2x the film size. Any input w ould be helpful..