NikonGear'23
Gear Talk => Lens Talk => Topic started by: Karsten on February 01, 2018, 16:28:02
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I'm new here. It was suggested to me to address this post to nfoto. Anyone's expert perspective on the following issue is welcomed and appreciated.
I recently acquired a Voigtlander 125 APO Macro lens in very nice shape except for a curious issue with the diaphragm. At various aperture settings, the shape of the iris is oddly misshapen. I have never seen something like this before, and I cannot tell whether this is a manufacturing defect or something that can be serviced, and most importantly what impact it might have on images.
Attached are photos at various settings.
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My 125 CV lenses are all packed for the upcoming move out of Oslo, so cannot make a direct comparison. However, this doesn't look that bad. I seriously doubt the slight unevenness will have any visible effect on the images.
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I concur with Bjørn; I have seen seriously lopsided and misshapen hexagons that still seemed to make no difference in the pictures. I'd use it normally and be observant in case the situation changes in the future.
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Hi, Karsten, apparently this is well within the tolerance. Yashica/Contax lenses branded Carl Zeiss were much worse in this respect: I had never seen any one sample that showed evenly shaped aperture iris.
The current DX AF-S 35/1.8 suffers the same but noticeably worse problem.
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If you trip the aperture lever with a finger, several times in a row, to simulate when it is actually mounted on the camera and stopping down and opening again, you will most likely see that it makes a circular opening,,,
Several reasons for the issue with it not looking round all the time:
The return spring is not very strong on these 125mm APO Lanthars,,,
The activating mechanism for the aperture has to go deep inside the lens due to the very long extension to reach 1:1
The movement is reversed inside mount, it's a universal lens build to fit many camera systems, unfortunately not with Nikon F as the main aperture stop down rotation direction,,,
The reversal movement is a strange rotating ring activated reversed by a rotating plate and a hook-shaped thing:
(https://farm6.staticflickr.com/5788/23508784736_c891daddd3_h.jpg) (https://flic.kr/p/BPoEEL)_EGL2051 (https://flic.kr/p/BPoEEL) by Erik Gunst Lund (https://www.flickr.com/photos/erik_lund/), on Flickr
Here is an image of the return spring for the aperture movement, here it is relocated due to it has one of Bjørns CPU build in (Ai-P)
(https://farm6.staticflickr.com/5659/23166898379_99cb323e8b_h.jpg) (https://flic.kr/p/BibpLp)_EGL2050 (https://flic.kr/p/BibpLp) by Erik Gunst Lund (https://www.flickr.com/photos/erik_lund/), on Flickr
Here you can see the CPU Contact block
(https://farm1.staticflickr.com/627/22906609104_b5cf61df55_h.jpg) (https://flic.kr/p/AUbmQh)_EGL2057 (https://flic.kr/p/AUbmQh) by Erik Gunst Lund (https://www.flickr.com/photos/erik_lund/), on Flickr
Just enjoy the lens ;)
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if you are really bothered by this then resetting the iris will help almost every time :o :o :o
several of my lenses were like this and only a resetting helped. like what was mentioned, this doesnt even look bad ::) i have seen worse where the iris looked like an egg
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I'll agree with those who say its not too bad. I wonder if slightly stronger spring might help? I hope some of the suggestions above will help.
I always check the aperture shape since I saw a very poorly formed one in a 55/2.8 AIS Micro-Nikkor. I've seen maybe one or two others. If the form is really bad it will show up in the pattern of out if focus highlights.
Dave Hartman
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In this thread you can see the complexity of the aperture linkage very well:
http://nikongear.net/revival/index.php/topic,2832.0.html
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It doesn't matter. Take it out for a week and you will see that you don't care anymore. ;D