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Back-focussing problem solved - via adapter

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waldo_posth View Drop Down
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Post Options Post Options   Quote waldo_posth Quote  Post ReplyReply Direct Link To This Post Topic: Back-focussing problem solved - via adapter
    Posted: 05 October 2020 at 18:26
This is just a short note on an adapter that has helped me to solve back-focussing problems with three lenses.
I have a number of old Contax lenses by Carl Zeiss. Some of them I have Leitax-ed to mount directly on my Sony A99/A99ii. But recently I relied on adapters for my E-mount cameras - e.g. by the Chinese maker KIPON - this is where the problem became "visible":

Three zoom lenses showed only insiufficient sharpness at the long end. Well, either I had got bad copies or they weren't as sharp as I had expected them to be (Zeiss' reputation for tele lenses is limited). However, my guess was that the choice of adapter would play a crucial role. So I already had decided to buy one of the really expensive Novoflex adapters for C/Y lenses to Sony E.

Fortunately I saw this adapter by Fotodiox - the Fotodiox Pro dlx Stretch adapter which was advertised as being able to solve back-focussing problems.

#1 Fotodiox adapter with case containing three ND filters (ND4, ND8, ND16)



#2 The ND filters can be installed within the adapter - they are magnetic



#3 ND filter installed



To be able to install ND filters within the adapter is a nice and practical feature. But that is kind of minor matter for me: Most important is that the adapter acts as a helicoid (which also decreases the MFD, BTW). After having mounted my "problem" lenses an 1/8 turn of the helicoid created insane sharpness at the long end of the their zoom ranges - problem solved!

The full-metal adapter is a very solid piece of work. If you have comparable problems I can only recommend this solution: You will disocover how good your lenses really are.

I have now got another one for the Minolta MC/MD-mount.

Edited by waldo_posth - 05 October 2020 at 23:17
"Stare, pry, listen, eavesdrop. Die knowing something. You are not here long." (Walker Evans)   http://www.flickr.com/photos/waldo_posth/
 



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addy landzaat View Drop Down
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Joined: 22 April 2006
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Post Options Post Options   Quote addy landzaat Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2020 at 19:09
So, the Kipon adapter did not allow for infinity focus? And you un-leitax'd them? As it is an C/Y adapter?

And the most important bit: where are the pictures you took?
Why not follow me on Instagram? @Addy_101
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waldo_posth View Drop Down
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Joined: 01 August 2012
Country: Germany
Location: Potsdam
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Post Options Post Options   Quote waldo_posth Quote  Post ReplyReply Direct Link To This Post Posted: 05 October 2020 at 22:14
No, I kept the Leitax adapters - I have only one Contax zoom lens that is leitax-ed - the 35-70mm. The backfocussing has been most salient with the 80-200mm and the 35-135mm, it's less obvious with the 28-85mm.

These are two images shot with the 80-200mm (long end):

#1 Probably @ F/5.6



#2 @ F/4.0


Both, the KIPON and a no-name adpater did not allow for infinity focus with the aforementioned zoom lenses - in a satisfying way. At inifinity the image was a bit blurred.
"Stare, pry, listen, eavesdrop. Die knowing something. You are not here long." (Walker Evans)   http://www.flickr.com/photos/waldo_posth/
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