>>3155441If you don't like the circular crop effect then diagonal fisheyes are the way to go.
16mm for FF, 10mm for APS-C and 8mm for MFT.
MFT has some nice and cheap C-mount lenses, APS-C has the Tokina 10-17mm zoom and Samyag/Rokinon primes and FF has the Canon 8-16 zoom, Nikon 8mm and the Zenitar 16mm. Pentax has the Tokina rebrand 10-17 and some Sigma diagonal primes for crop and the F 17-28 for full frame, plus Rokinon/Samyang 8mm and Zenitar diagonals.
Diagonals have close to 180°angles corner to corner and heavy distortion expected from a fisheye.
I myself like the more natural proportions of the fisheye image compared to the heavily skewed and streched out unnatural look of rectilinears.
