It's related, but it's no the reason they have shapely apertures. I think they are meant for imaging of things that are in focus (such as flat objects), so what the bokeh looks like is irrelevant. Much like in an enlarger, the enlarger lenses often have shapely apertures as they are only used in-focus.Originally Posted by redu
If you are shooting outdoors with thin DOF, especially in back-lit scenes, I'd prefer the lenses with rounder apertures.
Oh dear. Another entirely wrong-headed personal attack.
Why do you refuse to accept that my rankings of lenses are reproducible? And why do you refuse to understand that since I'm most concerned with on-axis performance -- remember, I shoot 2x3 so for lenses longer than around 100 mm performance far off axis isn't very important to me -- I've done many of my trials with the lenses hung in front of a Nikon.
Please stop telling me I'm wrong. Instead, tell us how you decide which lenses not to use.
GPS, I asked you a question. Please answer it.
I have tested the following lenses and have seen distinguisable and measurable differences between both resolution and contrast performances at M ~ 1:2.5
Caltar II N (Sironar N) 210 5.6
Computar Symmetrigon 210 6.3
G Claron 150 9
Hexanon GR-II 150 9
Macro Symmar HM 120 5.6
both at Fmax, f11, f22 and f45
The difficult part is to focus perfectly right and to keep the system stable during scan (f45 takes 26 minutes). Otherwise it is very easy to see the differences i.e As per contrast, Macro Symmar produces dynamic range greater than my Phase One Powerphase scanback's CCD can handle, while others don't. This is evident on the histogram. Resolutionwise a single meaningful pixel of information (considerable brightness and color change) in a 8400x6000 scan is perfectly perfect for a real sharp sharp lens; yielding 44+ lpm resolution at >= 60% modulation.
Likewise...
The hardest thing in the world to understand is the income tax. Albert Einstein
I answered your question. You don't have technical means to be able to test lenses resolution and contrast. That's why your lens "tests" are nothing more than amateurish ways of comparing pictures taken with different lenses.
When lenses are tested by those who have the means to do so, they don't use your eye to focus a lens, they don't use your fence and your Graflex camera, they don't even use your film holders etc. They have machines to focus aerial images on sensors in a process that avoids film, holders, your blinking eye and your shaking hand (now I nailed that focus, right on again...) etc. You're nowhere near to be able to say differences of 5-10 lines/mm with your amateurish means. Got it?
Read the gentlemen's post above -they all have their eyes, cameras with film and opinions about lenses they took pictures with. But only your pictures can say what lens is sharper - and unmistakably so.
I misspoke in my earlier post, I meant Repro-Clarons not C Clarons. Putting that aside, if the theories on why the shape of the aperture is relatively unimportant on a barrel mounted process lens are correct as above, then why would Repro Clarons go the opposite direction and have such complicated and intricate set ups in barrel mounts? Because the G Clarons were often used for enlarging and the Repros were not? Just curious.
Yes I got it.
But what I got is that you're not aware of what I've done or how well what I do discriminates between lenses. You're making assumptions and incorrect assertions, not measuring. Try measuring.
My speculation (totally unsupported by anything that might pass as fact) is that the Repro-Clarons came from an age when workmanship was held in high esteem in its own right and was not totally subservient to issues of selling price and profit. And also perhaps, it was a time when many general purpose taking lenses were sold in barrels so that Schneider had a range of barrels in production that were shared between their taking lenses and their process or enlarging lenses.
It might have also been a factor that when the Repro-Clarons were sold, they were competing with the Goerz Artars with their beautiful many-leaved apertures. I am sure that by the time that my G-Claron was made, that competitor had been neutralized.
It has a lot to do with vintage. Multi-bladed apertures are more typical on older lenses.
Someone else might be better than me at explaining whether this was simply due to
cost or alleged improvements in mechanical function. Certainly with some focal lengths, a simplification of the shutter allowed a significant reduction in shutter size and wt.
At least on the repro clarons I have (305, 355, 420) the fancy apertures were on fairly late production ones in factory barrels. My comments were all about barrel mounts, not shutters. I've ended up keeping the 355 and 420 in their barrel mounts, just bushed them to front mount on the Copal 2 shutter I use for the 305. Works great for 5X7.
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