I just put Asahi's 49mm metal hood on my 50mm f/2.0, no vignetting. Then I tried it on my 50mm 1.4. Very slight darkening at the very corners of the viewfinder. I suspect that if you want to use it on an f/1.8 or larger, it would work okay. The hood is marked for 1:3.5 135mm, 1:4 150mm and 1:5.6 200mm.
FWIW... Keith Whaley Alan Chan wrote: > > I have both the Pentax round and square (rectangular actually) hoods for > 50mm. They are both hard plastic. I am not aware of any metal 50mm hood from > Pentax. > >What's the consensus about Pentax own metal round hood for the FA 50mm's?
