Originally posted by elho_cid Interesting. I heard that some manual zooms could be worth having, namely the 70-210 and 35-105. Is there no AF alternative for them?
Some (but not many) old manual zooms are worth having. Tokina ATX, Vivitar Series 1, some (but not all) Pentaxes. Some are splendid -- and AF counterparts cost 10x-20x as much. Some, such as Tamron- and Samyang-made glass under various brands, may be quite decent, especially at bargain prices under US$20. Most are, at best, sub-standard by modern standards, but may be interesting for their 'character' (ie, don't expect great image quality).
One notable exception: the Schneider Betavaron 50-125/4-5.6 fixed-focus enlarger zoom, a weird-to-use beast, brutally sharp. I love it! It cost me US$70, marked down from US$3500. On 30mm extension so that it reaches infinity focus, it's an amazing general-photography lens.
Most modern zooms really are better than most older zooms. I have about a half-dozen each of old manual and newer AF zooms. Average cost of manuals: US$20. Average cost of AF's: US$280. Yow.
SR is a quandary. There's a formula for calculating a median focal length (FL) to tell the SR robot. I'll try to dig it up. Or, you can reset the SR FL with each FL change. Oy. Or, you can leave SR off and only shoot on a tripod or in bright light, just as we did Back In The Day before SR. When I mount my Vivitar Series 1 Version 1 70-210/3.5 onto my Spotmatic II, it's just my nerves vs the world. Same with the Sears-Tomioka 55-135/2.8. Going mano-a-mano with reality, eh? Manual zooms are not for wimps.
--- PS --- Some manual Pentax zooms are real turds. See the lens review database for the harsh truths.