brianc1959 Offline Upload & Sell: Off
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cyberstudio wrote:
Dudewithoutape wrote:
So you're saying with the correct testing and/or calculations, we can have optimal lens models to be used with the SB?
For example, Zeiss publishes where the exit pupils are in their datasheets. Take the Distagon 21/2.8, for example:
26.2 mm in front of the last lens vertex
and then you add the back focal distance, also in the datasheet.
37.0mm
So 56.2 fits within the sweet spot and it will probably have no vignetting (other than that from the lens itself). Strictly speaking this calculation is not 100% correct because it is not accounting for half the thickness of the rear element (back focus is the distance from the tallest point of the rear element from the sensor plane, so it differs from the last lens vertex by half the thickness of the rear element, a few mm's at most.)
Ok let me stop pretending to be an optical expert now, because I am not... and if I was mistaken I stand corrected in advance 
But unfortunately, Canon, Nikon and many others do not publish exit pupil data.
Actually, the exit pupil distance (measured from the image plane) is 37+26.2 = 63.2mm, which is just fine.
Thanks for pointing out that Zeiss supplied this information in their older data sheets. I never realized that before. Unfortunately, in their new data sheets (e.g., the ZF series) they ignore the exit pupil and only give data for the entrance pupil. Probably because of the current popularity of image stitching.
BTW, the back focal distance is measured from the last lens vertex to the image plane.
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