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06-09-2010, 07:03 AM   #1
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Lens Test: [645] 120mm vs 200mm vs 200 w/ TC

Hi all - as promised, I recently tested some new 645 lens acquisitions and thought I'd share the results with you all. Pixel peeping is a rarity with me so this is all you'll hear from me re: sharpness of my lenses

Crops are 100% on a 4000dpi Coolscan 9000 ED scan from Fuji Provia F. No filters or PPing applied. All were shot with a 645N on a tripod and cable release at f/11. Subject is a side-lit fake palm tree in incandescent light.

In the below images, the lenses used in each crop were as follows:
  • Top Left: 200mm f/4 FA with 1.4x TC
  • Top Right: 200mm f/4 FA
  • Bottom Left: 120mm f/4 FA Macro

My conclusions:
  1. The 120mm Macro is an incredible lens. I have never seen sharper scans
  2. The 200mm is still pretty sharp, but not as good as the 120mm. Nothing is!
  3. The 1.4X TC barely degrades image quality on the 200mm; I will no longer worry about losing IQ when using it. It even wins in some of the crops -- which suggests to me that focus is slightly different between the lenses.
  4. 645 lenses are pretty damn nice!

All in all, I'm going to use all of these with 100% confidence that I'm getting more detail than I'll ever need for my uses. Any thoughts?

Attached Images
       

Last edited by andycogbill; 06-09-2010 at 01:48 PM. Reason: Clarified that all lenses used were FA type.
06-09-2010, 01:44 PM   #2
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Hi, thanks for these comparisons, which do confirm how good that 120mm is - at least in sharpness. And a great result for the convertor!
But which versions did you use - A or FA lenses (as for the 200mm where it may matter)? Not that I think it will affect the conclusion, that it's safe to use any lens really in this system.
06-09-2010, 01:48 PM   #3
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Smolk - thanks for the reminder! All of my lenses are FA. I will adjust the initial post accordingly.
06-09-2010, 04:03 PM   #4
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It would be nice to see lp/mm numbers. I've seen one Mamiya 6x7 lens have up to a 109 which I thought was really good for that format.

06-09-2010, 06:30 PM   #5
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QuoteOriginally posted by tuco Quote
It would be nice to see lp/mm numbers. I've seen one Mamiya 6x7 lens have up to a 109 which I thought was really good for that format.
Can I generate these from a crop? Or are you saying you just want to see the numbers for reference?
06-09-2010, 08:05 PM   #6
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"It would be nice to see lp/mm numbers. I've seen one Mamiya 6x7 lens have up to a 109"

under controlled conditions, just about any high quality lens can obtain such figures, though I find people that state such things as absolute truth to be suspect. You rarely see such resolution in field conditions. besides there is a considerable resolution loss with various films - I'll believe it when I see it.

Don't worry about your 120mm it's fine, the 200mm doesn't do too badly all things considered. Though the FA* 645 300mm ED [IF] would be an interesting contender to throw into the ring.

Last edited by Digitalis; 06-09-2010 at 08:13 PM.
06-09-2010, 09:02 PM   #7
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QuoteOriginally posted by Digitalis Quote
under controlled conditions, just about any high quality lens can obtain such figures, though I find people that state such things as absolute truth to be suspect. You rarely see such resolution in field conditions. besides there is a considerable resolution loss with various films - I'll believe it when I see it.
The Zeiss and Pentax lenses in that data were in the 60's, 70's and 80's thereabout ( depending on aperture) and I assume they were done under the same controlled conditions. But if I recall only two lenses from each manufacture were tested. And note that 109 was not for all apertures, of course. I've been try to find that link. I should have booked marked it.

Last edited by tuco; 06-09-2010 at 09:17 PM.
06-09-2010, 09:37 PM   #8
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QuoteOriginally posted by tuco Quote
The Zeiss and Pentax lenses in that data were in the 60's, 70's and 80's thereabout ( depending on aperture) and I assume they were done under the same controlled conditions. But if I recall only two lenses from each manufacture were tested. And note that 109 was not for all apertures, of course. I've been try to find that link. I should have booked marked it.
I will also state for the record that RF lenses aren't the same as SLR lenses due to the fact that Range finder lenses do no have to compensate for the mirror that SLRs have therefore the optical designs are quite different. And in my opinion they cannot be truly compared, any Test where SLR and Range finder lenses are compared will be systemically biased.

06-10-2010, 06:14 AM   #9
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QuoteOriginally posted by Digitalis Quote
any Test where SLR and Range finder lenses are compared will be systemically biased.
Agreed. My friend's Mamiya 6 results make my Pentax scans look like they came from a Holga sometimes I always have to remind myself that my prints are still incredible AND I don't have to squint into the VF for several minutes just to focus!
06-14-2010, 11:19 AM   #10
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There is a reason why most tests of medium format lenses done at f/22 or at f/11 for that matter are given little credence. The significance of the results are affected by the diaphragm. Diffraction plays too much of a part. Most aberrations are reduced by the diaphragm, so one does not get a clear idea of how well corrected the optic is by judging it at those stops. Most medium format lenses become diffraction limited around f/11, so the differences you will see there will be from aberrations that are not affected by the diaphragm (lateral color, edge softness due to curvature of field and distortion). Yes, you will see differences in lenses at small stops but a better way to judge them is to compare them wide open.
06-14-2010, 11:26 AM   #11
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QuoteOriginally posted by desertscape Quote
There is a reason why most tests of medium format lenses done at f/22 or at f/11 for that matter are given little credence. The significance of the results are affected by the diaphragm. Diffraction plays too much of a part. Most aberrations are reduced by the diaphragm, so one does not get a clear idea of how well corrected the optic is by judging it at those stops. Most medium format lenses become diffraction limited around f/11, so the differences you will see there will be from aberrations that are not affected by the diaphragm (lateral color, edge softness due to curvature of field and distortion). Yes, you will see differences in lenses at small stops but a better way to judge them is to compare them wide open.
I use my lenses at f/11 MUCH, MUCH more often than I use them wide open. So, from my standpoint, this was a worthwhile test, as the samples are as close as they can be to a real-life scenario in a controlled environment.

This is also the first I'm hearing about MF lenses being diffraction-limited at f/11.... got any sources to back that up?
06-14-2010, 12:40 PM   #12
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QuoteOriginally posted by tuco Quote
...I've seen one Mamiya 6x7 lens have up to a 109 which I thought was really good for that format.
Over at the large format photography forum, Sandy King has seen over 100LP/mm with his 7II. He also came to the conclusion that a sharp 6x7 from that camera comes very close to equaling 4x5 large format shots for absolute detail at any given print size . Not tonality, grain, etc., but pure resolution. Anyway sorry OP for being off topic, I just wanted to comment on tuco's post.
06-15-2010, 09:53 AM   #13
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QuoteOriginally posted by andycogbill Quote
I use my lenses at f/11 MUCH, MUCH more often than I use them wide open. So, from my standpoint, this was a worthwhile test, as the samples are as close as they can be to a real-life scenario in a controlled environment.

This is also the first I'm hearing about MF lenses being diffraction-limited at f/11.... got any sources to back that up?

Interesting conversation. I found this interesting tidbit. Scroll down to "Sweet Spot and Format"

Depth of field and diffraction
06-15-2010, 03:46 PM   #14
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I have seen the f/11 figure used many times on various sites as the point where MF lenses become diffraction limited. The site listed above by Nightfly is but one example. The f/11 figure is a ballpark number because not all MF lenses are corrected the same. The 600mm Takumar does not become diffraction limited until at least f/16 due to longitudinal chromatic. The 55mm f/4 latest version is probably around f/5.6. The better corrected a lens is for aberrations, the wider the lens aperture will be where it becomes diffraction limited.
06-15-2010, 04:41 PM   #15
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Well the good news with all this diffraction limiting stuff is it doesn't stop you from taking a shot at *any* aperture the lens has. You can offset it with subject, composition and mood every time.
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