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Contax N->EOS adapter VS Conversion?

 
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lunarmouse



Joined: 27 Aug 2011
Posts: 3

PostPosted: Sat Jan 14, 2012 3:36 am    Post subject: Contax N->EOS adapter VS Conversion? Reply with quote

Hi all, I found that Kipon had made a contax 645-> eos/nikon adapter which could adjust the aperture; kinda interested in it so I emailed them if they would make N->EOS/Nikon adapter as well. They replied me saying "it's in pre-production" stage and would come out soon.

So... just wonder which direction I should go (and I really want to hear your advice/suggestions). I have N24-85, N70-300, and a N100 macro. Both options (adapter, conversion) have their own advantage and disadvantage:

Adapter: relatively cheaper (less than $300), do not need to modify the lens (which means the N body would not be thrown into the cupboard), but NO AF.

Conversion: AF, more reliable.

How would you guys think? Thanks!
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conurus
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Joined: 15 Aug 2006
Posts: 795
Location: Vancouver, Canada

PostPosted: Sat Jan 14, 2012 8:00 am    Post subject: Reply with quote

Thank you for your question. My answer has 2 parts: 1, it is inherently impossible to make a Contax N lens to Canon EF mount adapter while still maintaining infinity focus, and 2, lens designers go to great lengths to decide the optimal position of the aperture diaphragm in the lens design. The aperture diaphragm cannot be placed behind the glass elements and still expect to get full optical performance.

Our FAQ wrote:
Why don't you make an adapter which simply attaches to a N-mount lens?
It is impossible to make such an adapter because the N-mount has a very large diameter. Unfortunately, the original N-mount has to be removed to make room. This has nothing to do with the conurus circuit board at all but rather physical fitment - it is the same reason why it is impossible to make an adapter to mount Pentax K lenses to Nikon F mount, for example, without losing infinity focus.


The aperture diaphragm's placement is decided by the optical engineers who designed the lens. It can not be placed in a different position (e.g. at the rear of the lens) without affecting optical performance. Some users have reported success, but other users have reported problems such as vignetting in the corners but little increase in depth-of-field at all when the lens is "stopped down".

When we invest significantly on a Contax lens, obviously we want to get the maximum optical performance out of it. That means following Zeiss engineers' original intention of aperture diaphragm placement. Take some time to download some pdf datasheets from Zeiss. On each diagram showing all the lens elements of the lens design, the position of the aperture diaphragm is clearly marked.

http://lenses.zeiss.com/photo/en_DE/service/download_center/historical_data_sheets/historical_data_sheets_contax_n.html

_________________
I am a bird and I uncovered the E, EF and N-mount communication protocols!
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lunarmouse



Joined: 27 Aug 2011
Posts: 3

PostPosted: Tue Jan 17, 2012 4:15 pm    Post subject: Reply with quote

Hi thanks for your response -- now I think I know which way to go, just have to wait for a little bit for the 5D MKIII Very Happy
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