kshapero
South Florida Man
I have this lens in both Pentax K-mount and Leica thread mount, a favorite for its pleasant rendering. It has 7 elements in 6 groups arranged similarly to Pentax 50mm lenses; half-stops to f/16 with 9 diaphragm blades. Surprisingly longer than the 40mm M-Rokkor, but of course its optics were originally designed for clearing an SLR mirror, glass well-recessed at the rear. Thus it performs very well on digital RF cameras. It is 47.8mm long at infinity with the M bayonet-mount adapter in place. Features a focus tab. Worth noting is modest amount of barrel distortion.
Good to know.