Originally posted by grainbelt Before you go shopping, put the 55-300 on the KX and set it for a given focal length (55, 70, 85, 100). Shoot. See what focal length you tend to use, and which you feel are limiting.
Absolutely agreed. Asking what's a good portrait lens without doing at least that much to narrow the choices down is kind of like asking "what's a good vehicle" without at least figuring out first how big you need it to be.
Assuming you find you like things closer to the 50mm end of the range, any of the 50mm primes will work fine - and see the lens review section of this site for tons of opinions and samples. Takumar, btw,is the name Pentax used to give their lenses before they started using the Pentax name. These are mostly screw mount lenses. see the article on this site explaining the various types of lenses (there is a very recent thread in this forum by Adam pointing to it).
If you like things a bit longer, the DA70 and FA77 are both grwat, and there are dozens of existing threads comparing them. If you'd like to go cheaper with manual focus, the M85/2 and the relatively new Samyang 85/1.4 (sold under a variety of names) gets good reviews by most - just search this forum for references.
Or if you'd prefer a zoom, the DA*50-135 is pretty much the ideal range.