I find the 50 f1.4 lenses more special than the 50 f1.7 lenses by Pentax.
This is a Pentax-A 50mm F1.4 wide open:
This is a Pentax-m 50mm F1.7 wide open:
This is a Pentax FA 50mm F1.7 wide open:
Both 1.7 lenses perform quite similar (note that some difference in rendering is due to lighting differences). Also the Pentax-m was shot on the K-5, the other two on the K-1.
Keep in mind it is pretty difficult to focus wide aperture lenses at maximum aperture.
Last edited by D1N0; 07-08-2018 at 06:16 AM.
Reason: replace the FA 1.7 with a version with toned down exposure.