The paper probably isn't flat anyway. But if the image doesn't even look sharp to the eye unless the enlrgr lens is stopped way down, there is a substantial problem.
The paper probably isn't flat anyway. But if the image doesn't even look sharp to the eye unless the enlrgr lens is stopped way down, there is a substantial problem.
Of course, a bad alignment or a curled negative (and no 2 glass holder) can be addressed by stopping, with general performance loss...
paper should be flat, if we just curl it in the way that egdes go up then the easel mantains it flat. Then we have the vaccum easels, and the poor's man vacuum easel, this is a glass sheet sprayed with 3M Re Mount glue.
What I'm learning with the 1951 glass slide is that the lens can make some slight difference in some conditions, but the printer man (meat least) is who makes blurred prints
Silver gelatin photographic print paper is not capable of resolving all the information being blasted on to it by a high definition, high quality projection lens. In LPM terms, SGPP is limited to about 10 maybe 20 LPM and that is all folks. At f22, diffraction limited lens about 70 LPM. Added by square root means, the SGPP will never achieve 70 LPM. To believe a diffraction limited lens at f22 is not enough is myopic.
Consider what is the possible resolution of the human eye at a viewing distance of 12" ?
There are host of other factors involved, enlarger alignment, film flatness during projection, print paper flatness and a LOT more. On can obese and worry about all these details and become lost in these technical tunnels then totally forget about producing expressive art.
In the bigger picture, resolution is only one factor in the expressive qualities of a print. IMO, not worth obsessing over beyond a given result.
Bernice
For those who are obsessed about this:
http://cool.conservation-us.org/cool...resolution.pdf
And no, pushing for the limits of what is theoretically possible does not automatically result in expressive images, it just becomes a "thing" to over.
Bernice
Paper never limits perceptual sharpness. If you make a contact copy of a USAF 1951 glass slide you should see elements in Group 5, around 30Lp/mm for RC paper, and a bit less for FB paper (because fibers there), but this is way beyond what human eye can see.Originally Posted by Bernice Loui
A lens can be in trouble to resolve that much on the paper, if resolving 50Lp/mm on film then with a 5x manification this will be 10Lp/mm on the paper, also much less than the paper capabitily.
So in general paper resolves way, way more than lenses usually throw on it. To prove it, just take a really sharp negative, make a good contact copy (illuminator distance and pressure) on RC paper and see it with a x40 loupe.
Of course... by 1905 optical scientists were developing adjustable softer lenses because there was too much resolving power for portraits...
Exceptional resolving power can be great for some textures, or can be nasty because it adds pure noise on the soul of what it is expressed...
Pere, you're taking this discussion into what is known in Academia as mental masterbation. No longer a constructive discussion, just ... M
Done,
Bernice
Sorry, Bernice, no masterbation at all, you said "Silver gelatin photographic print paper is not capable of resolving all the information being blasted on to it by a high definition, high quality projection lens." and this pretty incorrect by far:
Ilford Gallery #2 80 lp/mm
Ilford Multigrade IV RC (no filter) 65+ lp/mm
old Agfa MCP RC (no filter) was 80-100 lp/mm
while an enlarging lens won't resolve more than 15lp/mm (from 75 in the negative) on paper at 5x scale, even with top notch glass.
Last edited by Pere Casals; 11-Mar-2018 at 13:57.
I also use certain of my enlarging lenses to make precision altered dupes or internegs on film, where a very high degree of optical correction and resolution is warranted. Ciba printing was analogous. It would hold a lot of detail. But all this was evaluated per real results. Never once did I crunch numbers.
Incidentally, certain enlarging lenses easily exceed the resolution of comparable focal length taking lenses. But I don't go to Aristotle for this information, but to the horse's mouth.
Just indulge thy troll, where did those "LPM" numbers come from?
-Note Fig# 9 in this publication, MFT plot of film -vs- paper.
https://pdfs.semanticscholar.org/f62...e42b533776.pdf
As for enlarging lenses, they DO exceed the MTF and image reproduction capabilities of print paper. Your assignment if you're interested, research the 6" f5.6 Goerz Magnar, what was this specialized enlarging lens used for, at what reproduction ration, it's optimal aperture, LPM spec at that aperture and what the Magnar was originally designed for. Then the problem of film to be projected and the projected image recording media flatness and alignment system becomes a serious consideration.
None of which has as much significance to expressive image making as tooted in all this Academia mental masterbation.
-As exampled in soft focus lenses and their related prints.
Bernice
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