Are ALL manual focus primes soft on XTrans cameras?

Started 6 months ago | Questions thread
Jim King
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Re: Registration distance vs lens construction
In reply to Tom Schum, 6 months ago

Tom Schum wrote:

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.

Interesting point, Tom - I hadn't considered that. Do you know whether or not the Rokinon 85 has a fixed rear element? Samyang, who actually produce this lens, is mute on that point: Samyang 85mm f1.4 lens. But it's certainly not a simple design, what with having IF and all that...

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