Originally posted by Wheatfield The fact is, if you are primarily a telephoto shooter, APS-C makes a lot of sense. I kept my K3 for that reason. I don't do a lot of long telephoto work, but when I do, I would rather use my 400/5.6 than my 600/5.6, for example, or my 600 by itself rather than my 600 and a teleconverter.
At the other end of the spectrum, full frame of larger makes more sense than APS-C if one is shooting short tele to wides. Both formats have their strengths and weaknesses. From the results I have been getting, full frame, ultimately, gives better images, but sometimes it's getting the image first, worrying about ultimate quality second that becomes important.
For me right now shooting sports has become a big deal with two kids in travel soccer. I'll take the slight image degradation from FF to APS-C if it means I can take full advantage of the fastest-focusing telephoto lens in the catalog. Also, most of my landscape work is when I'm traveling, so I very much like lenses like the 15mm LTD and the 21mm LTD, and I just got a nice used copy of the 20-40mm for when it's wet out. I could squeeze more out of a K-1 in some cases, sure, but for me APS-C is the sweet spot.