Remember, that particular example was for an 8x10 negative, so that is an 300mm lens. f/16 and f/11 are the best apertures based on the MTF curves for that lens. I didn't want to get in to details, but that lens is not 'flat' at 1:1, so I use f/16. I have measured the focus spread for that lens at 1:1 from edge to center and it is curved to the extent of 2.5mm at the baseboard. So it is no coincidence that I use f/16 for my 1:1 prints with that lens. Again, no surprises here as the manufacturer does not list 1:1 in the recommended magnification range of that lens.
Originally Posted by Kirk Keyes
A little OT, but to continue with these thoughts. If I were in a "Resolution Contest" with someone doing contact prints of 8x10, then my personal 0.15mm CoC may not be good enough. So a process lens (with a flat field) and good MFT curve at f5.6 may be needed. Again this is if the prints are going to being closely scrutinized side-by-side.
Now, that first example I gave (9x enlargerment) was more typical of a 35mm enlargement. I used f2.8 in that example, but, as you suggest, using a more realistic f8 would increase the focus spread way beyond 2mm, further discounting the 'paper thickness' myth.
Last edited by ic-racer; 04-27-2009 at 11:20 AM. Click to view previous post history.