Originally posted by twilhelm But, you can’t leave the 43 Limited out of the list
Indeed. I have an F 50/1.7 that I'm quite happy with. I wasn't really in the market for a new 50ish prime, but I put in a lowball bid on a 43 Limited, because it's a Limited. I happened to win it, so I've been able to do some comparison.
It is better. Not worlds better, not appreciably sharper, but better contrast overall and better control of veiling flare when facing the light. With metal construction, in an even smaller and lighter package. It's quite the little engineering marvel, and it's going to spend a lot of time on the front of my K-1.
The newer coatings on the FA 50/1.7 vs the F 50/1.7 might bring it up to a similar level. I don't think the differences are worth stressing about very much unless you find a screaming good deal, though - the F 50/1.7 is a fine lens.
As far as hoods for Pentax 50s go, the cheap-o
Fotasy 49mm screw-in does the job just fine. It takes a 58mm cap, and doesn't vignette if you stack it on top of a UV filter. I just leave it on my F 50/1.7 all the time, and I bought more for my Takumar 50s and 55s.