I understand that Sinar makes a sheet film holder that holds one sheet instead of two, and which is designed with a pressure plate to improve film flatness. I believe they also make a film holder where the film actually adheres to the holder. Has anyone actually tried either of these?
"The appearance of fine detail in a print is affected by MTF at frequencies quite a bit higher than 10 lp/mm. Even if you can't resolve separate lines, the information still makes a difference in the appearance of edges and of fine detail."
This is an interesting question. It's been studied quite a bit by perceptual physiologists and psychologists. There's no short answer, since the optical qualities of people's eyes differ, and since our vision is very sensitive to contrast. There's a big difference between the maximum resolution we can see in a backlit, etched bar target illuminated at ideal contrast vs. normal detail in a photograph.
Here are some numbers that may be interesting ... all of this presumes looking at something 10 inches away. The absolute maximum resolvable frequency of the human eye, assuming perfect optics and ideal contrast conditions is 14 lp/mm. A more typical maximum is 11 lp/mm. The maximum most people can see in high contrast image detail in a photograph is about 7 lp/mm. The maximum most people can see in moderate contrast image detail is around 5lp/mm.
The detail that makes a print look reasonably sharp is in the 1 lp/mm range. The detail that makes a print look very detailed is in the 5 lp/mm range. If you have excellent contrast in the 5 lp/mm range, the print will look very much like a contact print, regardless of the presence of detail at higher frequencies. Detail at frequenies higher than 10 lp/mm is completely irrelevent, however, in the digital world higher resolutions can help with issues unrelated to detail (aliasing, etc.).
"The appearance of fine detail in a print is affected by MTF at frequencies quite a bit higher than 10 lp/mm. Even if you can't resolve separate lines, the information still makes a difference in the appearance of edges and of fine detail"
this actually is not supported by any of the research that I've seen, or by any of my own experiments.
Paulr, what you're calling "resolution" isn't anywhere near the whole story about what the human visual system can discriminate.
The eye can perceive differences between a bar target (square wave) and a sine wave target up close to the limit of perceived "resolution", indicating that somehow the perceptual system is processing some of the higher harmonics that make the bar target "square".
Beyond that, there's a huge literature about what's called "vernier acuity", as distinct from "grating acuity" or "resolution acuity". A simple explanation and visual representation of the difference are here:
http://www.pc.ibm.com/ww/healthycomputing/vdt13eyee.html
Note the observation that vernier acuity is about ten times greater than minimum separable acuity. That may be a bit optimistic; but a quick scan of the PubMed database unearthed the following in a recent paper:
Vernier acuity, the psychophysical threshold for discriminating a spatial offset between two vertical lines, is one of the most sensitive measures of visual discrimination (10, 11). The vernier
acuity of human subjects can be as small as 6 seconds of arc (hereafter, sec arc) (10). Vernier acuity is considered hyperacuity because it is five times finer than resolution acuity (~30 sec arc, roughly the same as the foveal cone spacing; ref. 12). A similar relative level of hyperacuity in vernier tasks has been measured behaviorally in both cats (~1– 2 min arc) (13, 14) and monkeys (~10 sec arc) (15, 16). Because of the high level of psychophysical vernier acuity compared with the size of the smallest receptive fields (RFs), it is likely that information must
be integrated from multiple neurons to achieve perceptual discriminations.
Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3507-12.
www.pnas.org/cgi/reprint/102/9/3507
There are plenty more similar references where this one came from.
Sorry, I meant to make all of the hyperlinks "live":
www.pc.ibm.com/ww/healthycomputing/vdt13eyee.html
If you have excellent contrast in the 5 lp/mm range, the print will look very much like a contact print, regardless of the presence of detail at higher frequencies
"Very much like" is not the same thing as "indistinguishable from".
OK, enough for now...
...contact-print-junkie Oren
Just casting a vote, chiming in, the people who know better
than I do have already said it all -
Sometimes it all just comes down to magnification, whether it
is depth of focus, depth of field or how sharp the print looks.
When people figure out a near and far depth for tabletop, it is
always based on the accepted circle of confusion, which assumes
the final print size. So many compromises, so many variables
in day-to-day shooting - a little softer overall, or too shallow
focused area?
I've compared my results from Canon digitals, Fuji MF cameras
with fantastic lenses, 4x5 and 8x10. The Canon ones are filled
with all sorts of problems ( distortion, lack of edge sharpness, etc.)
however from the Fuji MF lenses through Fuji LF lenses on
8x10 - all have amazing sharpness when I'm not pushing the
envelope by shooting at f64 or f8.
I have 8x10's that you can count screws on a building flashing
at a distance of 150 feet. The trouble with the 8x10s is that
one needs a huge print to appreciate just how much detail
can be there. The Fuji 6x8 chromes just pop off the light
table - amazing - yet, similar shots with 8x10 seem to
hold gobs more detail.
The MF advantage seems to be that for reasonable
enlargements, there is less magnification in the shot for
tabletop or portrait work, so depth of field seems to be
more, as long as it's a moderate sized print. And MF is
easy to focus and hold still by comparison to LF too.
Sure, in a resolution test, people have shown than
MF lenses can resolve more - yet with less magnification, the
8x10 still appears to pull it all in, yet have smoothness and
lack of grain.
Let's see a 10 foot wide blowup of the
medium format vs. the 8x10 and then see how well
they hold up. The concert of all the factors will play out.
As a side note - I don't understand why so many people have
film flatness issues in *typical* 8x10 shots ( unless the camera
is pointed down or something ). Afterall, to "correct" distortions
or induce them, don't most shooters swing or tilt their backs
at times? I guess it depends on which lens and other things
( like magnification!). I mostly use Grafmatic backs for 4x5,
and I can't seem to find any issues with flatness - sharp edge
to edge, all across. Are there a bunch of bad film holders
out there? I have noticed that two cameras I bought had to
have thier GG / film plane height altered to work right, however
after that, all was well.
I think the person who wanted the reshoot was either using
a crummy loupe, or perhaps looking at some stuff that was
stopped way down for other considerations. I always hand
people a decent ( Schneider in this case ) loupe, and a large
one at that - it helps them wander around in there better.
Maybe she was looking through the diffused side of the protective
sleeve!
On the other hand, if the small or MF photo got the decisive
moment, in the right place, or was produced at a cost someone
could afford yet still fit the job - that's another discussion!
.
Um, no, it's not about "a crummy loupe." Let's reread the original post.
As the original poster said, "The girl had a point. Those sheets of color did not seem to my eye as “sharp” PER SQUARE INCH as 35mm and 120 roll film. Especially under a loupe."
So forget about enlargement factors: What the woman saw through a (1x1-inch?) loupe has nothing to do with enlargement factors, which we all agree gives an edge to 8x10 at a given *print size* (but not at an equivalent *enlargement factor,* e.g., 16x for 35mm compared to 16x for 8x10).
We can argue about why it is true (film flatness, film thickness, lens quality, etc.), but the fact remains: PER SQUARE INCH (i.e., enlargement issues aside), an 8x10 transparency will not match a square inch of a sharp 35mm transparency, period.
Or does anybody here really think that putting a loupe to an 8x10 chrome will show a 1x1-inch area that's as sharp as putting the same loupe to a 35mm slide? If so, I suspect I'm not the only one who'd like to hear more about your equipment and methods!
Interesting and new material here!
But really - the art person with the loupe just got the thing. She probably doesn't even know how to use it or what to look for. The loupe might be a real junker, too. (Could have made her day by screaming "Don't touch the film!". Oh God! We have to reshoot!") As long as the photographer got through to her and her company can write a check that resolves, hopefully, many digits to the left of the decimal point, it's all okay.
And what kinda boyfriend buys his lady a loupe? What's that all about?
Could it possibly that the 8x10 transparency was actually not sharp. We are all assuming that because this was taken for a client that the best technique was used, but then there are things like a misaligned ground glass, a warped film holder, etc, etc. That have ot been taken into account. I was curious, so I looked at one of my 8x10 negs taken with a Sironar N and one of my MF negs taken with a hasselblad and while the hassleblad negative has a slight edge, the 8x10 negative under a 4x loupe looks very sharp.
So I took scans of roughly the same area in both negatives, about 1 sq inch.
8x10
MF
I dont have a very good scanner since I only use it to proof negatives, but given that both images were taken with the same scanner, the errors from it apply to both images.
Something's wrong, Jorge.
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