Originally posted by Ben_Edict I see your arguments BUT I think the 1.7x AF-adapter may be the colourtful culprit. It introduces severe CAs, when attached to the 500/4.5 too - which the "real" Pentax tcs do not.
perhaps but it will also amplify the CA from the lens, and as I said, I had a chance to try the 60B with my TC and CA was much worse than the 300F4. At least that is what I saw on my camera with both lenses
Quote: The 60B has sure some CAs, but not more, than most other lenses of that fl. When used with the correct filters (the internal one and the front filter) CAs are even less obtrusive, as these filters seem to be part of the lens' computation.
Keep in mind that the intent of using the 60B or any 300mm F2.8 would be to combine it with one of my TCs for additional length. Therefore a lens that works well with the TC is paramount. As I said earlier, the 60B in my experience was not as good as I had expected, when used with the TC. I have thought about this long and hard, and for the moment, have decided to pass on this option, especially considering the K7 performance at higher ISO.
Quote: But obviously a FA 300/2.8 would be a much better choice...
Ben
I can't argue with this last point. I could possible consider as well an A 300F2.8 and use my 1.7X but I would have to try it first.