Plustek 120 Medium Format Scanner Lens Test Results

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palea
Posts: 34
Joined: Mon Dec 17, 2018 8:09 pm

Post by palea »

RobertOToole wrote:I need to make sure that I take a look at short focus with future testing!
Cool! I'll look forward to the details when your 150mms as tube lenses review is out (not seeing them on your website as yet).

My testing has been starting to move this way as well, though I've been thinking more in terms of creating something like a 500mm space rather than an infinity space. With stacked enlarger lenses it seems like short focus should suit for that. When stacking with most telephoto or telezooms it's necessary to push the tele off infinity focus to reduce the close focus limit, presumably with extension tubes. The amount of extension needed for full matching seems impractical but perhaps there's some modest benefit to using a bit of extension to nudge the tele's focus range into greater overlap with the enlarger lens. A potentially better corrected approach would be to pull a 150-200mm macro towards its close focus limit and see what happens.

A related configuration is three lens stacks where an enlarger lens provides conjugate translation between a scanner lens and a tube lens. I haven't pursued any math to investigate whether this might be worthwhile, largely because I'm unsure if 1) there's a case where this arrangement would accomplish something not possible with two lens stacks and 2) there's a somewhat affordable yet sufficiently well corrected enlarger lens as not to defeat the purpose of using a scanner lens.

rjlittlefield wrote:The absolute powers may match, but the signs are wrong.
Hi Rik, thanks for the catch; I've tidied the wording above. In general, I think I'm less concerned with the presence of a sign mismatch than the extent of the mismatch as function of subject, image, and aperture sizes. However, it seems something of academic exercise until someone finds with a useful operating point. The short conjugates of most interest are probably scanner lenses of roughly 35-105mm focal lengths. If one chooses a macro capable of focusing down to something comparable to twice a scanner lens's focal length the macro's focal length is too short to yield a magnification above 1x. So one might as well just use the macro on its own and not bother with stacking.

RobertOToole
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Post by RobertOToole »

palea wrote:
RobertOToole wrote:I need to make sure that I take a look at short focus with future testing!
Cool! I'll look forward to the details when your 150mms as tube lenses review is out (not seeing them on your website as yet).
Just enabled the page now: https://www.closeuphotography.com/150mm-tube-lens-test

It still needs some final editing for spelling errors etc, so let me know if you spot any errors, I'm sure there are a few.

In any case let me know what you think of the results. I am very pleasantly surprised how well almost all of the lenses performed.
My testing has been starting to move this way as well, though I've been thinking more in terms of creating something like a 500mm space rather than an infinity space. With stacked enlarger lenses it seems like short focus should suit for that. When stacking with most telephoto or telezooms it's necessary to push the tele off infinity focus to reduce the close focus limit, presumably with extension tubes. The amount of extension needed for full matching seems impractical but perhaps there's some modest benefit to using a bit of extension to nudge the tele's focus range into greater overlap with the enlarger lens. A potentially better corrected approach would be to pull a 150-200mm macro towards its close focus limit and see what happens.
I've moved away from Zooms and Macros as tube lenses and towards industrial line scan and EL lenses due to the simple that I find smaller lenses a lot easier to integrate these into my SM2 studio setup, which is very rigid, rather than using a large zoom which would need custom brackets and clamps to close to the same rigidity (Not to mention the costs of the optics themselves).
A related configuration is three lens stacks where an enlarger lens provides conjugate translation between a scanner lens and a tube lens. I haven't pursued any math to investigate whether this might be worthwhile, largely because I'm unsure if 1) there's a case where this arrangement would accomplish something not possible with two lens stacks and 2) there's a somewhat affordable yet sufficiently well corrected enlarger lens as not to defeat the purpose of using a scanner lens.
3 lenses, that's creative thinking :shock:

Best,

Robert

palea
Posts: 34
Joined: Mon Dec 17, 2018 8:09 pm

Post by palea »

RobertOToole wrote:It still needs some final editing for spelling errors etc, so let me know if you spot any errors, I'm sure there are a few.
Looks good to me, other than the 135mm link at the end pointing to the 2018 test, which is perhaps expected. As usual, my ranking of the lenses is somewhat different than yours where differences are small, which seems unsurprising as different people will prioritize different aspects of image quality. Among the six element f/5.6s in the test I'm not sure I see anything I'd place outside of the range of copy and history variation. I'd considered and passed over the G-Clarons on the basis of diffraction. And, having used similar lenses in the past, your results are about what I'd expect. My experience of four versus six element enlarger lenses is limited to reversing in the front but the corner differences are comparable to what you have with the Comparon. Towards the center I could discern no difference for the copies I was testing.
RobertOToole wrote:I find smaller lenses a lot easier to integrate these into my SM2 studio setup, which is very rigid, rather than using a large zoom which would need custom brackets and clamps to [get] close to the same rigidity.
Studio linear motion bracketing is convenient that way. I've a different set of requirements which make bolting a bunch of Thorlabs hardware to an Arca plate impractical, though there are times the vibration management would be helpful. Probably I should machine my own rail but that's a project for some other time.

dmillard
Posts: 595
Joined: Tue Oct 24, 2006 7:37 pm
Location: Austin, Texas

Re: Plustek 120 Medium Format Scanner Lens Test Results

Post by dmillard »

RobertOToole wrote:
The specs for this scanner are amazing, too good to be true of course, 5300 ppi, 60mm scan area, APO corrected, 8 element lens.

I would recommend the lens if you can find one of these scanners for a good price. They have been discontinued a couple of years ago and were sold under 4 different labels so we should see more on eBay more and more.

Questions, comments? Share them below.

Best,

Robert
Plustek is coming out with a new medium format scanner, which may increase the availability of their used ones for sale :)

http://downloads.plustek.com/downloads/ ... -00100.pdf

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