Reasons why no Nikon 85mm f1.2?

Started Apr 11, 2013 | Discussions thread
brightcolours
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Re: Reasons why no Nikon 85mm f1.2?
In reply to Photo Thoughts, Apr 13, 2013

Photo Thoughts wrote:

You'd have an 85mm, but not f/1.2.

Indeed, one would have to think the other way around, like a metabones speed booster. But then it only would be suable on APS-C anyway, not FF.

It would be kinda like this: a 127mm f1.8 lens, with enough space between the back element and the mount to fit a 0.666667x wide angle converter behind it. This would result in a 85mm f1.2, but with enough vignetting to be a "DX" (APS-C) only lens. Another problem will be that a 127mm f1.8 lens already will have a very big back element, maybe too big to work with the narrow F-mount. To overcome the DX-onlyness one would have to make many elements including the front ones oversized too.

I happen to have a 140mm f1.8 lens, which has enough clearance for a 0.6667x WC behind it. However, it is a very simple undercorrected design, without internal focus, without variable aperture (without anything making it suitable for 85mm f1.2 DSLR operation, actually). It is a 35-70mm film projector lens. To have it upto modern photography standards the design would have to be much more complex.

Another "possibility" would be to take a lens like a 200mm f2.8 lens and put a 0.425x wide angle converter behind it. Problems will be that a very high quality 0.425x wide angle converter will be very expensive, and that again you will have to oversize most elements of that 200mm design a lot to prevent it from being APS-C only.

For a reasonable lens design the bottleneck still remains the limited diameter of the F-mount.

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