K1 ii and FA 77mm Ltd.
I did some K mount 50-55mm lens comparisons this morning. K 55mm f1.8, K 50mm f1.4, Auto Revuenon 50mm f1.4, A 50mm f1.7, DA 50mm f1.8, A 50mm f2.8 Macro and K50mm f4 Macro. I won't bother you with the boring garden images. The camera was the K1 ii, tripod mounted set to 100 ISO. Each lens was set to f5.6 (my go to starter aperture for most of my photos) and the shutter speed came in at 1/125 sec for each shot taken with the 2 sec self timer. All were focused to infinity (the infinity focus was accurate for each lens according to the camera's focus confirmation system). There were a few surprises...
The weakest lenses when zoomed on were the two macro ones. At up to 100% magnification my eyes could see no discernible difference in resolution between any of the group.
I could barely tell any difference in colour rendition between any of the Pentax lenses, but the AR 50mm produced by far the warmest rendition. The pictures were taken facing away from the light between 8 am and 8:15 am this bright, sunny morning. Indoors and in lower light this lens usually produces a much cooler cast than the Pentax ones. So it seems to exaggerate whatever the ambient colour temperature is.
There were very slight variations in the field of view between most of the 50mm lenses, but that of the K 50mm f1.4 was appreciably narrower than the rest but only when compared side by side. The 55mm was obviously the narrowest FOV as expected.
On the K1 ii I have been disappointed with the performance of a couple of these lenses at table top distances - the K 55mm and K 50mm f4. Both perform admirably for this purpose on my K3 and KP. For general landscape or walk about use though I would be happy to use any of these lenses. For normal viewing at normal distances you can't really tell them apart except for the narrower FOV of the K 55mm and the colour rendition of the AR.