cross posting this with the ultra thin filter stack thread since it seems relevant – here is a contax g 28/2.8 comparison between stock a7, kolari v4 (UT) a7, and reversed optosigma pcx 1.5m filter on stock a7. i shot the kolari v4 a7 + g28 combo focused in the center, outer midzone, and corner to give a feel for the level of field curvature remaining. i only focused the pcx filter shots in the center because i didn't see any real difference between focus locations moving outward with the pcx filter. the kolari is clearly better in the center and midzone, but it's quite close in the extreme corner.
