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Archive 2013 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF

  
 
Dustobub
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p.1 #1 · p.1 #1 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


I picked up a CV 35 1.4 this past week and have just gotten around to shooting with it this morning. I like the handling of the lens, and for the price, it seems like a reasonable RF 35mm solution for the A7R until Zeiss comes out with native FE manual lenses next year.

While the vignetting is extremely strong WO, there is no visible color shift or highly noticeable smearing in the corners. However, I'm a little concerned that either I have a slightly defective copy, or the lens+A7R combo just has some very strange field curvature.

Take a look at these photos (see Dropbox for full all photos at full res). The wall shot is at f4 and almost MFD while the other shot is around 100ft-infinity and from f1.4 to f11 (I did refocus between f2 and f2.8 to account for focus shift). Interestingly, the extreme corners are actually in pretty good shape, but there is a very pronounced ring that is out of focus, and it doesn't really go away until f8.

I've never shot with the CV 35 1.4 before. Is this the normal type of field curvature it exhibits?

Thanks,
Dustin











Edited on Dec 15, 2013 at 01:37 PM · View previous versions



Dec 15, 2013 at 12:07 PM
douglasf13
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p.1 #2 · p.1 #2 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


I'm not able to look at the files up close at the moment, but it makes sense to me. The 35/1.4 had some of the stronger field curvature that I've seen on NEX cameras with soft corners, and it's possible that there is a heavy ZONE B dip that affects aps-c corners, and then things get better again in ZONE C for FF corners. My guess is that it is normal.


Dec 15, 2013 at 01:21 PM
Makten
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p.1 #3 · p.1 #3 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


I saw the same thing with Voigtländer 40/1.4 on a7. I don't think it's curvature of field, but just lower resolution and as Douglas said; the midzone dip. Voigtländer don't seem to publish MTF graphs, but many Leica M lenses behaves like this too. Just look at the MFT for the very expensive 35 'cron and 'lux ASPH.

Edit: The closeup is particularly interesting, where you can clearly see that resolution is higher in the corners than in zone B.



Dec 15, 2013 at 01:28 PM
Dustobub
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p.1 #4 · p.1 #4 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


Interesting. In doing a little more testing it does seem like regardless of focus I can't seem to get Zone B to really clear up. Does seem to point to just resolution rather than field curvature. Bugger. Will have to give it some more real world testing to see if it affects my liking of it. It's a serious drop in resolution, and I'll be shooting it mostly at 2.8-4 where it is pretty noticeable. We'll see... Thanks.


Dec 15, 2013 at 01:36 PM
douglasf13
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p.1 #5 · p.1 #5 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


Dustobub wrote:
Interesting. In doing a little more testing it does seem like regardless of focus I can't seem to get Zone B to really clear up. Does seem to point to just resolution rather than field curvature. Bugger. Will have to give it some more real world testing to see if it affects my liking of it. It's a serious drop in resolution, and I'll be shooting it mostly at 2.8-4 where it is pretty noticeable. We'll see... Thanks.


This lens is generally considered to be good for people and photojournalism shots, more than flat or landscape type photos.



Dec 15, 2013 at 01:44 PM
jojomon11
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p.1 #6 · p.1 #6 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


Is this version I or II?

Version I had some focus shift in some copies



Dec 15, 2013 at 01:46 PM
douglasf13
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p.1 #7 · p.1 #7 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


jojomon11 wrote:
Is this version I or II?


I believe you're thinking of the 35/1.2, not the 35/1.4. The 35/1.4 comes in single and multi coat options.

p.s. focus shift isn't an issue if you're focusing at shooting aperture.



Dec 15, 2013 at 01:48 PM
jojomon11
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p.1 #8 · p.1 #8 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


Thanks Douglas your right I was thinking 1.2, late night


Dec 15, 2013 at 01:50 PM
sebboh
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p.1 #9 · p.1 #9 · Voigtlander 35 1.4 on A7R - Field Curvature / MTF


yeah, this is normal. my understanding is that the cv 35/1.4 is modeled after the leica m 35/1.4 lux pre-asph which also shows this midzone dip.




Dec 15, 2013 at 01:57 PM





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