Plustek 120 Medium Format Scanner Lens Test Results

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RobertOToole
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Plustek 120 Medium Format Scanner Lens Test Results

Post by RobertOToole »

Image

Found this lens on eBay as 'parts only' for about $100 earlier this year. Finished the test in may or june but my medical issue hit right before I was able to get it online but now I'm finally getting caught up, although I still have 2 or 3 test ready to finish and post. But I'm making progress! :(

https://www.closeuphotography.com/plust ... -lens-test

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

Lens is easy to extract and measures out at 50mm f/3.92. So far I've only tested the lens with the A6300 (APS-C), I did plan to test it with a newer body but the medical issue in June changed my plans :shock:


The full size file at 1.7x is really good looking, send me a PM if you would like to see it, the 2500 px file is also nice.

Click on the thumbnail below for the 2500px image, you can right or two-finger click and save as also.


Image


Filmscanners.info got a decent resolution out of it at 3450 ppi, which is very good. https://filmscanner.info/en/PlustekOpticFilm120.html

Overall the lens is very good, better than most that I've tested but its not at the level of a Scanner-Nikkor 14 element or the Minolta 5400 lens of course.

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

chris_ma
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Post by chris_ma »

hi Robert,

very glad your back in full testing mode but please tackle the load with leisure and take care of yourself.

the plustek might be an interesting option for those who need something in this focal length or as you say find one on the cheap.

one thing that just came to mind:
this could be a nice option for a stacked setup with a 100mm lens at 2:1.
did you ever test that? (or even crazier idea, the minolta 5400 at 3x)?

I seem to remember somebody (might even have been you) writing that stacking lenses optimised for macro (or otherwise highly corrected) often works not as well as one you hope and simpler lenses with smaller mag generally do better.
or maybe my memory is just playing tricks.

bests
chris

RobertOToole
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Post by RobertOToole »

chris_ma wrote:hi Robert,

very glad your back in full testing mode but please tackle the load with leisure and take care of yourself.

the plustek might be an interesting option for those who need something in this focal length or as you say find one on the cheap.

one thing that just came to mind:
this could be a nice option for a stacked setup with a 100mm lens at 2:1.
did you ever test that? (or even crazier idea, the minolta 5400 at 3x)?

I seem to remember somebody (might even have been you) writing that stacking lenses optimised for macro (or otherwise highly corrected) often works not as well as one you hope and simpler lenses with smaller mag generally do better.
or maybe my memory is just playing tricks.

bests
chris

Hi Chris,

Did not mention it but I did test the Plustek on a tube lens, and the result was not unusual for a scanner lens, it failed. Center was okay but the corners were hopelessly poor. I've also tried the Minolta 5400 a couple of times with the same results. The Canon MP-35 center is beautiful but the corners are gone.

That sounds like something I said. Good memory. It appears that really well corrected lenses, like a Macro Varon, work wonderful on extension but they really badly on a tube lens. On the other hand lenses that are okay or just average on extension, like a Componon 4/28 or 4/35, put these on a good tube lens and they work beautifully on a tube, no CAs, great corners, excellent all around.

Best,

Robert

chris_ma
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Post by chris_ma »

RobertOToole wrote:It appears that really well corrected lenses, like a Macro Varon, work wonderful on extension but they really badly on a tube lens. On the other hand lenses that are okay or just average on extension, like a Componon 4/28 or 4/35, put these on a good tube lens and they work beautifully on a tube, no CAs, great corners, excellent all around.
that's really interesting.
I wonder why no lens manufacturer uses this principle to make a low cost high mag lens. seems to me that building a lens by simply combining a Componon on a Macro Symmar would be rather cost effective (just build a new lens barrel which holds all of the lens elements) and would result in a hard to match price to performance ratio.

RobertOToole
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Post by RobertOToole »

chris_ma wrote:
RobertOToole wrote:It appears that really well corrected lenses, like a Macro Varon, work wonderful on extension but they really badly on a tube lens. On the other hand lenses that are okay or just average on extension, like a Componon 4/28 or 4/35, put these on a good tube lens and they work beautifully on a tube, no CAs, great corners, excellent all around.
that's really interesting.
I wonder why no lens manufacturer uses this principle to make a low cost high mag lens. seems to me that building a lens by simply combining a Componon on a Macro Symmar would be rather cost effective (just build a new lens barrel which holds all of the lens elements) and would result in a hard to match price to performance ratio.
Manufacturers do this to some extent. In one of my old macro photography slide shows (I do photography for a living) I used to include images from Nikon that show a optical layout for some objective, like a 60x or 80x/0.90 APO, then a stepper lens for photolithography with that exact same design at the front of the stepper. It was really interesting. So it looks like they just assembled two optics to make a new and more highly corrected one.

Wonder if I can dig up the diagram? :shock:

Best,

Robert

Scarodactyl
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Post by Scarodactyl »

It feels really odd to me that tube lenses work that way. I would have thought you'd need a less-corrected tube lens to compensate for a less-corrected lens (just in opposite directions, as with compensating eyepieces). But of course if you use compensating eyepieces on an already-well-corrected objective the result is very poor, and I would imagine the same is true with microscope tube lenses (ie, using a nikon objective on a zeiss scope).

kaleun96
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Post by kaleun96 »

Thanks for the test Robert. I had been waiting for that page to update, previously you had the cover photo for the page but it linked to an empty page I think.

I've been browsing these scanners on eBay for some time but waiting for one to come up at a reasonable price in the UK or elsewhere in Europe. Good to know they are worth taking a punt on.
- Cam

Lou Jost
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Post by Lou Jost »

When comparing lenses whose image circles are different, it is sometimes worth thinking about the total resolution in lines per FOV. For example, if one scanner lens has an image circle of 30mm and resolves 100 lines per millimeter, and another with an image circle of 60mm resolves 50 lines per mm with the same FOV as the first lens (so m twice that of the first lens), then really both lenses are transmitting an equal amount of information, and we could get exactly the same image from either one (though we'd have to stack-and-stitch with shifted sensor for the second).

RobertOToole
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Post by RobertOToole »

kaleun96 wrote:Thanks for the test Robert. I had been waiting for that page to update, previously you had the cover photo for the page but it linked to an empty page I think.

I've been browsing these scanners on eBay for some time but waiting for one to come up at a reasonable price in the UK or elsewhere in Europe. Good to know they are worth taking a punt on.
Sorry about that, the page was just about done then my hospital stay and the first weeks out was tough. I experienced lots of memory issues, basically a big blank for the week in the hospital and about the week prior was wiped clean. If you would have asked me if I ever tested the plustek when I was just out of the hospital I would have told you no, the plustek 120? never tried it. :shock:

There is one scanner up, the pacific image, primeFilm model, is ending in 2 days and currently at $50. Hope no one from here was already bidding.... :oops:

Robert

kaleun96
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Post by kaleun96 »

RobertOToole wrote:
kaleun96 wrote:Thanks for the test Robert. I had been waiting for that page to update, previously you had the cover photo for the page but it linked to an empty page I think.

I've been browsing these scanners on eBay for some time but waiting for one to come up at a reasonable price in the UK or elsewhere in Europe. Good to know they are worth taking a punt on.
Sorry about that, the page was just about done then my hospital stay and the first weeks out was tough. I experienced lots of memory issues, basically a big blank for the week in the hospital and about the week prior was wiped clean. If you would have asked me if I ever tested the plustek when I was just out of the hospital I would have told you no, the plustek 120? never tried it. :shock:

There is one scanner up, the pacific image, primeFilm model, is ending in 2 days and currently at $50. Hope no one from here was already bidding.... :oops:

Robert
No worries, I thought that might be the case (not that you need a reason!).

I see these Plustek scanners have varying effective resolutions according to filmscanner. Some as high as 3800 PPI and some as low as 2900-3000 I think it was.
- Cam

mawyatt
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Post by mawyatt »

RobertOToole wrote:
chris_ma wrote:hi Robert,

very glad your back in full testing mode but please tackle the load with leisure and take care of yourself.

the plustek might be an interesting option for those who need something in this focal length or as you say find one on the cheap.

one thing that just came to mind:
this could be a nice option for a stacked setup with a 100mm lens at 2:1.
did you ever test that? (or even crazier idea, the minolta 5400 at 3x)?

I seem to remember somebody (might even have been you) writing that stacking lenses optimised for macro (or otherwise highly corrected) often works not as well as one you hope and simpler lenses with smaller mag generally do better.
or maybe my memory is just playing tricks.

bests
chris

Hi Chris,

Did not mention it but I did test the Plustek on a tube lens, and the result was not unusual for a scanner lens, it failed. Center was okay but the corners were hopelessly poor. I've also tried the Minolta 5400 a couple of times with the same results. The Canon MP-35 center is beautiful but the corners are gone.

That sounds like something I said. Good memory. It appears that really well corrected lenses, like a Macro Varon, work wonderful on extension but they really badly on a tube lens. On the other hand lenses that are okay or just average on extension, like a Componon 4/28 or 4/35, put these on a good tube lens and they work beautifully on a tube, no CAs, great corners, excellent all around.

Best,

Robert
Robert, Chris,

Awhile back I purchased the Rokinon (Samyang) 135mm F2, this was the sharpest lens edge to edge I've owned and probably a direct copy of a Zeiss since it had the same specs. Being this sharp edge to edge infers a very well "corrected lens".

My thinking was this should make a superb tube lens, testing proved to NOT be the case, it was horrible with the Mitutoyo 5 & 10X. Another (Steve) on here got the same results on a Sony mount, I use Nikon.

However, it did work well when stacked with a old 50mm reversed Nikon D lens.

This somewhat confirms that a "well corrected" lens are not a good indicator of a good tube lens. The Raynox and Thor Labs are simple lens, so probably not "well corrected", but make superb tube lenses.

When image stacking a lens with a good center but soft edges may not be so bad IF the edges are sharp at a different focus point from the center since stacking should help with apparent edge softness.

Anyway, thanks for all the lens testing work!

Now back to my obsession with these nanometer level piezo devices!

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

RobertOToole
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Post by RobertOToole »

kaleun96 wrote: No worries, I thought that might be the case (not that you need a reason!).

I see these Plustek scanners have varying effective resolutions according to filmscanner. Some as high as 3800 PPI and some as low as 2900-3000 I think it was.

Yes, I did notice that. Some of the manufacturers hand-pick the better lenses? The Plustek model slightly better higher resolution I think right? Or which was it?

The Plustek 120 lens are nicely finished but other scanner lenses I've seen out of China, from Polaroid and Pacific image, look like something that was underwater for awhile, then dried in a rock tumbler, then shipped to the assembly plant in a bucket. Resolution numbers from sample to sample must be all over the place with scanner lenses I can imagine. :lol:

Best,

Robert

palea
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Post by palea »

RobertOToole wrote:It appears that really well corrected lenses, like a Macro Varon, work wonderful on extension but they really badly on a tube lens. On the other hand lenses that are okay or just average on extension, like a Componon 4/28 or 4/35, put these on a good tube lens and they work beautifully on a tube
Hi Robert, doesn't this follow almost by definition? Macro and scanner lenses are optimized for use at a short finite - short finite conjugate ratio, enlarger lenses are optimized for short finite - long finite, and tube lenses are intended for infinite - finite use. The long finite (print) side of an enlarger lens is presumably going to match a tube lens focused at infinity better than a short finite design.

A testable prediction from the conjugate ratios is, if the tube lens can accommodate it, focusing the tube lens at distances closer than infinity should improve performance when the other lens isn't infinity corrected. With enlarger lenses the best tube focus distance would presumably be the one corresponding to the manufacturer's preferred magnification for the enlarger lens (d = M f, often around 400-600 mm). However, since performance is already good at infinity, the potential for improvement seems likely to be small. This is probably a way of saying a conjugate distance of several hundred mm isn't greatly different from an infinite one in terms of ray angles.

A macro lens at close focus is perhaps a natural close finite match for a scanner lens on distance though, as Rik points out below, ray angles are subject to increasing mismatch as magnification increases. I have neither a scanner lens or a tube lens to test with but this also may not be suitable for epi illumination as working distances are probably quite short.

mawyatt wrote:The Raynox and Thor Labs are simple lens, so probably not "well corrected", but make superb tube lenses.
Hi Mike, well corrected should be fine so long as it's well corrected for the right things. Since Raynox DCRs are intended for use as close up lenses on telephotos with limited close focus distances they should be optimized for providing a long to infinite conjugate to the telephoto when the subject plane is near their focal length. Reversed, that makes them much like a tube lens.

Thorlabs doesn't appear to disclose their tube lens design---the Zemax models are indicated as black box---but for what they charge for their lenses I would hope they're well designed and manufactured for their purpose, which seems consistent with Robert's overall best rating in his tube lens test. From the dimension drawings I'm unsure if double Gauss or similar designs can be excluded.

A search is giving me lots of hits repeating the 135 f/2 complaint but not posts with test results supporting that conclusion. I suspect Rik may have already indicated the difficulty in other contexts but am hesitant to suggest a linkage without direct supporting evidence. Indirect evidence (some which comes from your observations of using other 135 mm lenses as tube lenses :wink:) does admit interpretations where level of correction isn't the trouble.

Scarodactyl wrote:I would imagine the same is true with microscope tube lenses (ie, using a nikon objective on a zeiss scope).
I don't see why it wouldn't be. From a practical standpoint the trouble is that, unless one's designing the whole system, it's unlikely to be able to match compensating aberrations well enough to produce results competitive with those from independent correction.
Last edited by palea on Sat Oct 26, 2019 10:38 am, edited 2 times in total.

RobertOToole
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Post by RobertOToole »

palea wrote: A testable prediction from the conjugate ratios is, if the tube lens can accommodate it, focusing the tube lens at distances closer than infinity should improve performance when the other lens isn't infinity corrected. With enlarger lenses the best tube focus distance would presumably be the one corresponding to the manufacturer's preferred magnification for the enlarger lens (d = M f, often around 400-600 mm). However, since performance is already good at infinity, the potential for improvement seems likely to be small. This is probably a way of saying a conjugate distance of several hundred mm isn't greatly different from an infinite one in terms of ray angles.
Hi Palea,

Thanks for sharing your ideas. This comment in particular is interesting. I've found this to be true in testing, some, almost all actually, really do seem to improve when focused closer than infinity, I call it short focus, when stacked with other lenses. Sharpness seems to increase and CAs seem to cancel out. In my last tube lens test that I just finished very recently, 150mm enlarger lenses as rear lenses, I did test for short focus with the top finisher and it did perform as expected. I need to make sure that I take a look at short focus with future testing!

All the best,

Robert

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Post by rjlittlefield »

palea wrote:A macro lens at close focus seems like a natural close finite match for a scanner lens.
I disagree. The scanner lens will be optimized to produce light rays that are converging toward the image plane on the back side. But the macro lens at close focus will be optimized to accept light rays that are diverging away from its intended subject. The absolute powers may match, but the signs are wrong.

--Rik

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