I post this question in the DSLR forum, as the lenses adressed are mostly used here...
I consider to use a Canon mount fisheye zoom lens with a MFT housing using Metabones adapter (Oly EM5MII UW (native MFT FE zoom lenses do not exist)) and wonder wich combination may be better:
#1.: Canon 8-15mm FE (FF) with Metabones Canon EF to MFT x1 adapter. Diagonal angle of view (AOV) would be 175-80 degrees then.
=> Optimum AOV, but probably a lot of light is lost as only fraction of image circle used for sensor image (but lens bigger, so supposedly a lot of light there...)?
#2.: Tokina 10-17mm FE (APS-C) with Metabones Canon EF to MFT x0,71 booster. AOV: 180-105 degrees.
=> gain of light (aperture), because of x0,71 booster, but vignetting may be strong as more of the image circle of the lens is projected to sensor (crop 1,42x) compared to APS-C sensor w/o booster (crop 1,53x-1,62x depending on model). Metabones claims that by the use of speedboosters sharpness is even imrpoved (I guess this may be the case for low quality lenses, likely not for high quality ones)...
Grateful for comments.
Edited by Architeuthis, 08 March 2018 - 12:15 AM.