Heh Tom. My opinions of the FA 28 are based on pretty extensive use with and *istDS (6MP) and relatively little use with a K10D. I don't think it's every seen my K5, since by the time I had my K5 I already owned an FA 31 limited and the DA 21, both of which crush the FA 28 for contrast and punch. But obviously the DA won't cover a full frame, and the FA 31 costs many times what the 28 does, and isn't as wide.
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Yeah I compared it closely to the (mark I) kit lens and 16-45 back in the day and couldn't see enough differences to justify it over either. The only thing it brought was compact size and the f/2.8 max aperture. But those two lenses were the widest ones I had anyway so I was likely to have them in the bag either way, which is why the 28 got little use. On FF, however, I can totally see the use for it, because it's then like the DA 21 or DA 15: a tiny sharp prime that's easy to bring along if you don't want the weight of a beheamouth like the 15-30 in your bag and they other lenses you are carrying don't include a standard zoom like the 24-70.
No,
Yes, I think the FA 28 2.8 is a good choice. I agree completely with KLM's comments. I tested the lens briefly on my A7r and found it very sharp into the corners at mid apertures. Contrast and flare resistance very good. I won't comment on wide open performance because that was not part of my test. The main reason I'm not using it with the A7r is that I have a non-Pentax MF lens that is equally good optically and more convenient to focus on the A7r. The FA lens continues to be a permanent part of my Pentax APS-C setup.
