Reasons why no Nikon 85mm f1.2?

Started Apr 11, 2013 | Discussions thread
Michael Benveniste
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Re: Reasons why no Nikon 85mm f1.2?
In reply to str8pipe, Apr 13, 2013

I don't know if any f/1.2 AF lens is feasible in Nikon mount, but I'm more uncertain that an 85mm f/1.2 would be less feasible than a 50mm f/1.2.  The "front focal length" determines the minimum needed size of the front element group, but when it comes to the rear element size the back focal length is of vastly more importance.  That's in part why rangefinder cameras have smaller lenses than SLR's.

Recent patents for fast Nikon lenses like the 28mm f/1.8 show a back focal length of 38mm, give or take a tenth.  I may be using the wrong formula, but to illuminate the corners of an FX frame at f/1.2 from that distance would require a rear element of at least 38.1mm of usable optical diameter, and from what I can tell the pin arrangement limits things to 37.5mm.  So it's a very near thing. 
As I've hypothesized before, if Nikon came up with an alternate "out-of-mount" way for the camera and lens to communicate they could make f/1.2 lenses.  A couple of patents have hinted at this, but I've seen no evidence of it being real.

I do know is that Nikon and 3rd party lens makers have had 25+ years to make an AF f/1.2 lens in Nikon mount and so far all we've seen are designs on paper.  I also know that Canon made a 50mm f/1.0L lens but discontinued it.  It may be that market forces explain the lack more than physics.

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