Pentax has a dazzlingly confusing array of lenses with similar
range and speed .. which one of these would you guys recommend?
D-FA 50-200 f4-5.6,
A good performer, specially designed for digital with extra coatings and extra low dispersion glass to give an above average performance of it's price. This would definately be my choice.
Has excellent reputation, but hard to find (production stopped many years ago).
Easy to find and with good performance.
No longer made, can be hard to find. Good performance.
Replaced by the FA J 75-300, a good performer but is getting harder and harder to find.
Oh, an old one and with power zoom function. Large and heavy, unbalanced on the DS. Not easy to find (was a poor seller).
You miss one...
Essentially the same as the FA version, but without power zoom. This means that it's lighter (but still heavy). I have it myself and I'm really longing for the DA 50-200 instead since that one is better balanced on my DS. The FA/F 100-300 is not for handholding...
Also, how do the Tamron or Sigma 70-300 "macros" compare to these?
Tamron AF 70-300 LD is good, Sigma 70-300 APO is good, non APO not as good - but Sigma has problem with sample variations. That is - some APO's are very good, some are not as good as the non APO's. You never know until you tried the actual unit... Tamron has a more consistent quality.
Take care