I am in sort of dilemma for getting some good (-old) FA medium zoom for all round...
..I saw few of them in second hand shop and on e-bay, so dilemma is:
FA 28-70/4, FA 24-90/3,5-4,5, FA 28-105/3,2-4,5 or ????
Witch one is better... sharper... with more contrast and better bokkeh ?
the FA28-70/4 is a nice compact constant f4 with a non-rotating front element so its nice for manual metering and using circular polarizers. It was considered the "good" kit lens for a while. But I think "good" is like the current 18-55 is good.
However, this model also has a design or manufacturing flaw. It is not uncommon to develop a separated lens element. It will look "fogged". The only quote for repair that I received on mine was around $100... and by the way look at this new Tamron 28-200 ...
The 28-70 has a rotating front element. The other two are IF.
I am almost certain the 28-70 and 28-105 I had were bad copies so they might both actually be OK in a best case.
The 28-105 and 24-90 seem to be really saturated which may or may not be a good thing. I like all of the FA lenses more than the DAs in part for this reason.
I haven't tried the PZ lenses but the 28-105/4-5.6 is said to be good.
Of the original three you mentioned, they're all not built great, but they're acceptable. If anything, my 28-105/3.2-4.5 was slightly tighter than the 24-90
This power zoom lenses cost more in second hand / e-bay and I read & hear that are not on some very good reputation (not better quality).
I think the quality issue is a misnomer, the PZ lenses are prone to damage at the power zoom function switch, but that does not actually impact manual zoom function or lens function at all, and besides, aside from powering the zoom function which can replace manual zooming with motorized zoom, none of the new Pentax DSLRs support any of the zoom during exposure, image size tracking, and predictive zoom/focus, or other power zoom functions such as preset focal legths.
They also have a somewhat "cheap" feel to them, refarding some "looseness" or play of the front group of elements, but optically these are good lenses
I am interested are those FA lenses (FA 28-70/4, FA 24-90/3,5-4,5, FA 28-105/3,2-4,5) equal quality (sharpness) like kit DA18-55 /50-200.. or better.. like DA16-45/4 (...or even more better) ?
(Is possible some comparation with DA zoom lenses for sharpness/quolity illustration)
Check this link. It compares DA16-45/4, FA24-90, FA35/2, FA50/2.8. I am very impressed at how the DA16-45 perform against some of the very fine lenses.