K-01 mount adapter question

Started May 4, 2012 | Discussions thread
Gerry Winterbourne
Veteran MemberPosts: 7,468
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Re: K-01 mount adapter question
In reply to brandrx, May 4, 2012

brandrx wrote:

MaxIso wrote:

so im planning my purchase, probly getting the k-01 next month, if not then the k5. i know there are mount adapters for the k-01 to use canon and nikon lenses, anybody know if they have sony adapters? my local camera store said they werent sure and would have to contact the manufacturer. thx for any info.

The registration distance of the K-mount is 45.46mm and the regitration distance of the Sony AF / Minolta AF is 44.6mm.

Therefore if there were an adapter for Sony lens on Pentax K-mount body it would have to have correction elements. If It does not have correction elements then focusing to infinity would be impossible.

You need to be very careful about using correction adapters. Some can wreck the resolution of lenses, especially away from the centre. My experience is very limited - I've studied one example in any detail, which was one my brother was trying on a Nikon body. What he did was shoot a test chart quite close (so infinity focus wasn't an isue) with Tamron 90/2.5 at f/5.6 on D700 without the adapter and then with it.

Centre resolution was about 5% lower when using the adapter. Edge resolution was much worse but I couldn't get a meaningful measure. At the time I was looking at this I got the impression that the converter - just a single element - was not corrected for spherical aberrations, which would explain why it got so much softer at the edges.

The adapter also altered the FOV by about 15% - in effect it operates as a very low magnification TC. You could search here for threads discussing the merits and demerits of TCs. One problem is that TCs can give different IQ with different lenses, so you might expect that infinity correction might also be variable from lens to lens.

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Gerry

First camera 1953, first Pentax 1985, first DSLR 2006
http://www.pbase.com/gerrywinterbourne

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