View Single Post
Old 11th February 2013   #260
brianc1959
Member
 
Join Date: Jun 2009
Posts: 48
Re: Speed booster for NEX

Quote:
Originally Posted by Vivek View Post
John, It is consistent with that lens' behavior on FF.

See: http://lenses.zeiss.com/content/dam/..._35-70mm_e.pdf

All the Contax/Yashica Zeiss lenses data (barring the 100/3.5 Sonnar): Contax-Yashica


Is your infinity focus correct at f/3.4?
Hi Vivek:
Thanks for posting the Zeiss data sheet. Using the published exit pupil data for the 35-70/3.4 I was able to check the SB design and can verify that the SB itself won't contribute any vignetting at all at the 35mm end. In other words, 100% of the vignetting seen in John's 35mm/3.4 test shot (25mm f/2.4 actual) is due to the attached zoom lens.

The exit pupil distance of the 35-70mm/3.4 grows from 57mm to 78.6mm as you zoom from 35mm to 70mm. For an exit pupil distance of 78.6mm its possible to get a trace of vignetting in the extreme corner with the Speed Booster, but most likely the zoom lens blocks the pertinent rays before they even get to the SB so that the SB effectively contributes no vignetting throughout the zoom range.
brianc1959 is offline   Reply With Quote