Originally posted by crewl1 I don't plan to use the K-1 for telephoto work as it seems an APSC camera such as K-3 would let me fill more of the sensor with the target and provide maximum number of pixels for post processing work.
Is there something wrong with my thought process here?
Same here. Having been hooked on something like the K1 sensor via the Sony A7R, I definitely want a K1, but I see no reason to replace my K3 bodies for most of my birding. One exception are large Sandhill cranes which have almost no fear of humans. For cranes fairly close, the Pentax A400 at F/8 to F/11 is gorgeous at 36mp, and the lower noise of the FF sensor lets me go about a stop faster on the ISO if I need to up the shutter speed on take off or landing.
For most other birds, I have found FF wastes more weight and pixels than it is worth. Of course in my current FF configuration, I am giving up AF, too. That will happen somewhat less with the K1, but the DA*300 with or without converter will be hard to duplicate on FF.