Originally posted by krypticide Lots of focal lengths in the title...but it says it all.
My latest lens acquisition was the 43mm, which I absolutely love. When I want a prime on my camera, I always think of the 43mm. So the FA 50mm and FA 35mm aren't feeling any love. Should I sell them both and get the FA 31mm?
Despite the FL's being relatively close, the 31 and 43 are sufficiently different lenses that owning both is by no means superfluous. I would indeed get the 31 since you have two lenses to sell and offset the cost somewhat. If you turn out to have a clear favorite between the 31 and 43 you can sell the other and move on to the 77 or the 55. All are wonderful.
Each of the three amigos has fans that consider it the best of the bunch, no matter what papersack says. The 55 was designed by Pentax's most accomplished lens designer, so there should be no surprise that it too is a top-notch lens, though it does have a bit different personality than the FA Ltds.
There's a good used market for all of these lenses so you're really not risking much by trying them out. Enjoy the journey!