Originally posted by bertwert I am not just basing it off my K-50 experience - it's a fact that you'll have less detail at f/16 and ISO 25600 than if you're shooting at f/4 and ISO 1600.
As far as focusing, comparing the K-50 and KP is apples to oranges as you say, but the specs state that the KP's AF sensor is 2 steps more sensitive. In dim evening light, I can unreliably confirm focus at f/5.6 (with the K-50) - so let's say f/11 on the KP (half a stop more than f/9.5 of the 55-300 at 300 and TC). Unreliable AF isn't fun and leads to missed shots, especially with fast moving wildlife.
I have never claimed to be shooting at f/16 .... f/9 is plenty, and I have not noticed poorer detail around ISO 9000 than at lower levels.
The "K-3ii replacement", which we are supposedly talking about here, may have even better ISO performance and better AF than the KP does;
use of AF does not depend on aperture shooting at since focusing occurs at maximum opening, and as I've already said, my KP has not provided unreliable AF at dusk/dawn problems.
But this is missing the point; we do not expect Pentax to provide an extra processor to handle AF; those who want it, may be out of luck on this aspect, which Pentax does not claim to be an area of strength for any of their cameras.