btw, 80 square inches at 900dpi is 64.8million pixels, if my multiplication is accurate...
btw, 80 square inches at 900dpi is 64.8million pixels, if my multiplication is accurate...
Once you've scanned the print and applied PS controls like sharpening, you're learning a lot more about your digital skills and the idiosyncrasies of the digital pathway than about the lens. Cumulatively, this is can be important to personal
workflow, but pretty much obscures an objective evaluation of the lens in the first
place. In fact, once you shoot a piece of film you start losing critical information.
An ordinary film plane isn't flat, unless you've got astronomical-grade glass plates
or a vacuum back, and the characteristics of film dye clouds or silver grain have
an effect in themselves. Fortunately, a precisely aligned view camera acts just like
an optical bench; and with a good groundglass and serious magnifier we can learn
a lot about our lenses. For example, yesterday was a good day for long-distance
viewing, so I took my Sinar with its 28-inch bellows up a hill for infinity lens tests.
I rarely use my 450 Fuji C on 4X5 though often on 8x10, and a new thing I learned
it that it is extremely sharp at infinity even wide open. With a max aperture of f/12
and using only the center of a huge image circle, this was no surprise. But at that
kind of bellows extension even the slight gust of wind will mess up the image, and
it's nice to know that I can shoot that particular lens at very distant scenes a couple
of stops faster than I was previously accustomed to. Of course, I still want to stop
the lens down a little due to any potential uneveness of the film itself.
Yes, but given that wind is not, in itself, a lens aberration, and the use of a longer lens will be more forgiving to focal plane intolerance, due to increased depth of focus, is this point just a little bit moot?
Sharpening, when applied sympathetically, should not draw any more attention to itself than softening, so I'm willing to accept the best from any optical system-
even visual acuity over resolution, if you must...
+1. Always.Originally Posted by Policar
Bruce Watson
A couple of things, when I wrote,"... one should have this knowledge and use it to determine if f64 serves the situation and outcome that you desire." it's purpose was to state that one should be aware of the resolution sacrifice one makes in using f64 but that sometimes f64 is what is required regardless of the consequence.
This was a common situation with me during my years as an advertising still life photographer. I routinely had to photograph cosmetics on 8x10 film at life size magnification, sometimes greater than life size. And even with all the movements available to me on a monorail view camera it was still not possible to get focus on all the planes of focus created by cosmetics standing, leaning, laying, moving back into perspective etc all in the same scene. Sometimes the camera would look like it was not even possible to have light pass through the bellows with all the compound tilts, rises, and swings in use. And it became necessary to shoot the scene at f64 or even f90. And while the scene would look in focus, it would not have the degree of sharpness that I was accustomed to. I would then have to weigh the final usage of this image.
If the image was merely going to appear in a magazine then f64 or f90 would suffice. If the image were to be used on a large sales display or poster in a store, with people being able to walk up to it and examine it closely, then the scene would be broken up into two images, with focus and aperture optimized for each, and then spliced together.
Joseph - Utterly not moot. It's the difference between a good shot and a wasted one.
Depth of field and camera shake are two different problems. In this case, on my 8x10 the 450 lens is supported by quite a bit of mass with respect to both the camera itself and a big tripod; in addition, the negative needs far less enlargement. On the 4x5 just a little vibration at this kind of extension with ruin the shot for any use I have in mind. Second, being sloppy with focus is symptomatic of inevitabley being sloppy with something else. Each of those little things add up to a cumulative effect. It's just like the folks who stop their enlarging lenses way down because they never bothered to correctly align their enlargers in the first place, or don't want to bother with glass carriers. If that suits someone's taste, that's their preference. But those are the kind of people who probably get their developer contaminated with fixer or have aphids crawling across the sensors in their DLSR's. Not my style.
FWIW,
10 inches x 2666 pixels is 26,660
8 inches x 2666 pixels is 21,238
The product of the two is 568,604,480 , or 568 megapixels...
That's only the number of pixels, and not the resolution... of course. Also, of course, I don't believe the resolution is less than 1/5. But that's just me.
Lenny
Drew, you mentioned using 28inch bellows and the unevenness of the film itself; my point was that depth of focus, the tolerance of film placement on the image side, is increased in that particular situation. I didn't mention Depth of field in relation to your post.
Each of the other factors you mention have little to do with the original topic, and just serve to add variables that will confuse things, so I won't go there-
Lenny, you've already said that 72MP is patently ridiculous, even though, by Policar's estimation, the image you've displayed has been downsampled to 900 spi- is this a fair estimation?
If it is, then we might not have hit bottom even yet; further downsampling might produce a sharper image than the detail displayed here. With the added benefit of increasing depth of field...
Perhaps posting the 2666 spi scan might help clear things up a bit-
maybe there is more information in the original scan that is being lost to compression? or some other reason?
The premise of your original post-
- well, that, at least to me, is debatable- unless you refuse to accept debate.I have heard plenty of trash talk about the resolution of large camera lenses over the past few years. I have also heard that one should never close all the way down.
Well, I've just done the test for myself and I say its not true - at least for me - in the least. ...
Not that it matters to me much, I'll draw my own conclusions no matter how things are spun, based on the evidence presented-
However, since maximizing depth of field is the stated aim of a few here, it leaves me wondering why smaller formats aren't used- perhaps greater depth of field would be slightly easier to achieve that way-
You say - "The calculated numbers in a previous post about 72mp being the max for an 8x10 are patently ridiculous."
well, I don't find it ridiculous, but I'm open to being convinced otherwise-
if your 2666spi sample contains a lot more resolution than is shown in the reduction, then I'll be happy to accept it-
But as it is, I can only accept what I can see for myself-
If a microscopic scanning of the film grain is the purpose of the exercise, then I'm sure it has been a successful one- however, if the purpose is to disprove the existence of diffraction effects, well, on the evidence, I remain unconvinced-
The numbers in your last post have little meaning to me, you might have chosen 3000, or 4000 instead...
Of course, maybe I'm just adding to the trash talk-
Lenny, here's a small sample of developers affecting sharpness in negatives.
What degree of magnification are we seeing here ?
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