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PostPosted: Sat Jun 07, 2014 9:57 am 
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Hi folks,

I don't often link to articles off-site these days but this is such a shocker there's no question in my mind it needs to be done.


It totally cured me of any temptation I might have had to buy Leica M glass for my m4/3rds camera! But the implications are wider and if you are planning on buying a fast lens designed for a camera system other than the one you plan to use it on then do your research first and, if at all possible, rent a copy to test with before parting with too much hard cash. Of course it hasn't escaped my notice that the article above was produced by Lens Rentals so one might argue that they have a vested interest in publishing such a report but I'll give them the benefit of the doubt on this one.

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Sat Jun 07, 2014 10:19 am 
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Interesting article. I recall first seeing the effect in the lens design notes of the Coastal Optics 60mm, which is a lens still on my dream list. It was stated the lens was designed for about 2mm filter thickness.

From: http://diglloyd.com/articles/CoastalOpt ... notes.html
Quote:
When designing the 60mm f/4 I called several people who were doing IR and UVIR camera conversions, and was told that DSLR filter thicknesses ranged from ~1mm to more than 3mm. There is no standard thickness, unfortunately. However, I had to pick something, and 2mm seemed like a reasonable compromise. It seems that this choice might be a very good match for a standard Canon 5D, since the filter pack is 1.45mm thick and the coverslip is probably ~0.5mm thick. Making a small error in filter thickness has a fairly minor effect on the aberrations, and even omitting it altogether will not cause a drastic reduction in performance. After all, any lens designed for film cameras will automatically have aberrations induced by the sensor glass when used on a digital camera, but very few people notice this effect.


I hope the mass market 3rd party manufacturers (Sigma, Tamron, Zeiss etc.) take care of this effect for any lens class they design. It would be interesting to see if MFT is an outlier in sensor thickness. For example, do Fuji X/Sony former-NEX/Canon M systems follow the 2mm-ish filter found on DSLRs, or is there a good reason for the thicker filter? Where a lens is shared between systems, this could have an additional impact. For example, in mirrorless land we seem to be seeing two groups already with the APS-C crowd lead by Sony and Fuji, vs. the MFT duo Olympus and Panasonic. The crop factor differences only emphasises the differences between them.

Fortunately for me, I don't really do adapted lenses. I did get some cheapies for MFT while I was using the system so performance was never high on the list anyway. I also have converted a Canon FD 50mm f/1.2 to EF, and even within expectations for a budget lens, its performance was a bit underwhelming. Perhaps this is an effect of the filter thickness? I could try it on my astro-mod cam (front filter pack removed) for comparison.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Sat Jun 07, 2014 10:50 am 
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Interesting article indeed. Thanks for posting

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PostPosted: Thu Jun 12, 2014 1:05 pm 
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It was a very good read. I always assumed that lenses adapted for another system would probably not give amazing results since it's not a tailored combination but this was a bit more dramatic that I expected.

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PostPosted: Sat Jun 14, 2014 10:07 am 
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For those that check that site less regularly than me, they did a follow up article.

http://www.lensrentals.com/blog/2014/06 ... -it-matter

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Mon Jun 16, 2014 9:16 am 
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Hi popo,

Good catch. It would seem that the system most likely to be affected is m4/3rds with a physical/optical thickness roughly twice that of most of the competition as, Leica excepted, the other manufacturers don't have wildly different sensor stack thicknesses. Just as well that m4/3rds is already blessed with a good lens system and one that continues to improve. 8)

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Mon Jun 16, 2014 11:36 am 
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Reasons for using adapted lenses vary, for cost, or perhaps to get something that isn't already available. Maybe because you have another system lens already to reuse. So I don't think the issue is insignificant, if not overly important given the lack of complaints in general. It is a minor effect outside of perhaps the fastest glass.

As mentioned before, where I think it may have more of an impact is with 3rd party multi-system lenses. The lower end ones may not care, but if you want a premium lens there is already the sensor size difference to account for, and on top of that the filter thickness may steer the design into two separate design groups. As an example, I wonder if this may have contributed to Zeiss not releasing their Touit range on MFT. While the normal lenses may end up at odd focal lengths, their macro would still be interesting one to have if all they had to do was swap the mount over.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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PostPosted: Mon Jun 16, 2014 12:08 pm 
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Hi popo,

You may well be right about Zeiss! That extra couple of millimetres of glass (or similar) might well be enough to cause the red and blue light cones to focus at different heights above and below the sensor when compared to green unless the design was specifically optimised for m4/3rds. There's a name for that sort of aberration but with an aberrant brain I can't recall it right now! :oops: :lol:

Bob.

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Olympus OM-D E-M1 + M.Zuiko Digital ED 12-40mm f/2.8, Lumix 7-14mm f/4, Leica DG Summilux 15mm f/1.7 ASPH, M.Zuiko Digital 45mm 1:1.8, M.Zuiko Digital ED 75mm 1:1.8.
Leica D Vario-Elmar 14mm-150mm f/3.5 - f/5.6 ASPH.
OM-D E-M5, H-PS14042E, Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.


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PostPosted: Tue Jun 17, 2014 7:16 pm 
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Photographers may call it longitudinal chromatic aberration, believe the lens designer term is spherochromatism, but I could be out on either! But the lensrental article doesn't cover that aspect only focusing on MTF curves. Again, for what would be sold as a high performing lens, that may tip the balance between them wanting to sell it or not.

_________________
Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.


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