Flektogon 20mm f:4. My new old lens… 🙂
This is the predecessor of 2.8/20, lens optimized for aperture at the cost of distortion. The original 20/4 has almost perfect edge-to-edge rectilinear correction. The above frame was not altered geometrically in any way (well, except for plain rotation & border crop after scanning). The lowest stair steps are unsharp – they are out of DOF, the glass is sharp to the edge (of course, sharpness is better mid-field, but corner softness is not that much).
Just don’t put it on dSLR…
BTW: There’s a lot of heat as whether 2.8 or 4 is better, don’t shoot at me: I don’t care. If this lens fails me, I’ll ditch it and try something else, I won’t change a tool that works for me.
