Are ALL manual focus primes soft on XTrans cameras?

Started Mar 13, 2014 | Questions thread
Tom Schum
Tom Schum Veteran Member • Posts: 7,175
Re: Registration distance vs lens construction

R Neuschul wrote:

That would somewhat depend on lens and the extent and which way [+/-] the adapter was off.

General principle remains true: registration distance is important.

I agree that when the entire set of optics moves in and out to focus, the exact length of the adapter is less important, but when a lens built for a certain registration distance such as in Nikon uses INTERNAL elements to focus, the length of the adaptor can be very important.

This is because the rear element of the lens may remain stationary in such a lens and the distance between this non-moving element and the image plane is an important constant in the lens design.

It's nice to see Samyang and Rokinon and Bower lenses in Fuji X mount because the lens manufacturer now controls the registration distance exactly.  Should be easy to get optimum performance with these variants.  I have two Samyang lenses in x mount, the 8mm F2.8 fisheye and the 300mm F6.3 mirror tele.  They are both very good on my X-E1, and the 85mm x mount is getting more and more attractive to me because I really like that focal length (price looks real good too).

I also use M42 lenses on my X-E1 with adapters.  Quite a few of these lenses move the rear element (or the entire set of optics) when focusing.  These work very well with low-cost adapters.

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Tom Schum

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