Here's a suggestion: Don't buy a 300mm now. Wait a year, save up your money, then buy a 300/2.8 (Tokina or Tamron SP). Then, add one or more teleconverters (1.4X, 1.7X, 2X) and you'll have a 300/2.8, a 460/4, a 510/5, and a 600/5.6.
I didn't do that, and felt a bit stupid seeing my 300/4.5 (Rikenon) and 400/5.6 (Pentax PKA). For not much more, I could have found a 300/2.8. I just sold the 400 because I hardly ever used it. (I shoot people, not birds.) All the Takumar and Pentax 300/4 and 300/4.5 lenses will satisfy you; the F and FA are the sharpest. One user wrote that when he received his first prints taken with the F, he wept because the quality was so good, like the quality you get from a 50mm lens. Most birdwatchers say that 300 is too short for birdwatching. 400 is the entry level. But if you buy a 400/5.6, you will find it too dark to use with a teleconverter. If you're happy with 400mm, that's OK. The best is the 400/5.6 PKA. It was a big advance over the SMC and M and is even sharp at f/5.6. Among third-party 400/5.6s, the Sigma 400/5.6 APO Macro is probably the best. Among older third-party manual-focus 400/5.6s, the best is the Tokina RMC (Rainbow Multi Coating), which came before the AT-X. But it is hard to find. For about $500 on EBay, you can find a Takumar 500/4.5 in M42 screwmount. Fit it with a Pentax 1.4XL teleconverter, and you have a PK 700/6.3. See my message from earlier in January, in which I recommend long, fast lenses for M42. (Search for "Piesker".) [EMAIL PROTECTED]
