Stacking Low Cost Enlarger Lenses For High-End Image Quality

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Lou Jost
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Post by Lou Jost »

I think both forms of test are extremely useful. and in fact I would add a third kind of test to my wish list, a test using an actual stack of a difficult 3-D subject. These can show problems (or lack thereof) that might be missed by MTF tests and single shots of flat objects. For example, some kinds of CA can disappear after stacking, while others don't.

I really like the degree of standardization of Robert's tests, and if a lens performs well on his tests, I know it will stack well too. I also like the way that Miljenko's tests can allow us to rank lenses more objectively than we otherwise could. But there are important things that we cannot tell from the center and corner resolution figures. Astigmatism, for example.

I think diversity is healthy in this field. It is hard and tedious to make tests of any kind, and so we should encourage people to make the tests that best motivate THEM. All these tests are useful and are filling gaps that would otherwise have no data at all. In just the last year or two the amount of data that has been generated on this site is incredible, and I feel like we are turining a corner now, with demonstrated high-quality solutions for almost every magnification. Thanks, testers!!

Miljenko
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Post by Miljenko »

Nicely said, Lou. You nailed it 100%.
Best rgrds.
Miljenko
All things are number - Pythagoras

elimoss
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Post by elimoss »

RobertOToole wrote:
Also as far as I know, no MTF lens test site or manufacturer shares MTF data at close up distances or magnification.
Woah there. I'm sure we have seen where Schneider shares MTF data at different B values. I wouldn't be surprised if some other industrial lens makers did too.

I can't recall seeing that sort of thing on any consumer lens data.

RobertOToole
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Post by RobertOToole »

elimoss wrote:
RobertOToole wrote:
Also as far as I know, no MTF lens test site or manufacturer shares MTF data at close up distances or magnification.
Woah there. I'm sure we have seen where Schneider shares MTF data at different B values. I wouldn't be surprised if some other industrial lens makers did too.

I can't recall seeing that sort of thing on any consumer lens data.
Was thinking consumer macro lenses data but I did not specify that, good catch, my error.

Industrial lens info sheets usually do post MTF at magnification. Those are all simulations of course based on an ideal virtual lens.

It is a strange though that all the MTF test sites that I visited, only Mark Goodman's posts MTF curves at magnification for macro lenses. I did see Lens Rentals run a macro lens test at magnification but they only posted data for maximum aperture, or maybe I missed it?

Thanks.

Robert

AlxndrBrg
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Post by AlxndrBrg »

As this is the newest thread among the "incredible results with stacked lenses" bombs that have shown up, I'll ask here:

Has anyone tried using the ITL200 as the tube lens in these tests with a low cost enlarger lens at the front? I know its far from the cheapest tube lens, but seeing as its widely used among the Mitty users, and its high quality, it would be interesting to see how it compares. And as I'm hopefully getting my mittens on a Mitty setup of my own soonish, I'm curious :wink:

elimoss
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Post by elimoss »

RobertOToole wrote: I did see Lens Rentals run a macro lens test at magnification but they only posted data for maximum aperture, or maybe I missed it?

Robert
Yep, lensrentals usually posts MTF at maximum aperture, focused on axis at infinity. This is apparently the best way for them to establish whether their inventory is performing up to spec.

They have another interesting one they have been showing from time to time, the best individual point MTF (BIF). This shows the best possible resolution at a distance away from the optical axis, when actually focused there. So that one is useful for focus stacking.

RobertOToole
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Post by RobertOToole »

AlxndrBrg wrote:As this is the newest thread among the "incredible results with stacked lenses" bombs that have shown up, I'll ask here:

Has anyone tried using the ITL200 as the tube lens in these tests with a low cost enlarger lens at the front? I know its far from the cheapest tube lens, but seeing as its widely used among the Mitty users, and its high quality, it would be interesting to see how it compares. And as I'm hopefully getting my mittens on a Mitty setup of my own soonish, I'm curious :wink:
Yes. I have tried ITL200+ITL200, stacked tube lenses :shock:, and ITL-200 + some of the shorter schneider lenses. The results promising but the longer focal length gave me a 7x+ so a shorter lens like the Raynox 125mm was a better. I am sure there is a longer front lens that will work really well with the ITL-200 so I need to try some other combos when I have some free time.

So many combos to try, so little time :D

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