Originally posted by falconeye I'll make a shot, outlining how a full frame Pentax should look IMHO.
I'll collect feed-back and may write a blog article outlining a camera which may create enough interest. Here we go...
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Yeah, I could go for this camera though I would classify it as a semi-pro model. This would leave them free to add a pro level FF in the future, and also move the successor for the K-r up half a tier, and add an entry level model below that, possibly mirrorless.
A couple other thoughts: I can't help but noticing that it is a mere 1mm wider than the K20d, I think that is about the right size despite what other people will argue. Foregoing SR is crazy, and when you add the better AF system that everyone is wanting, it ends up being about the size of the K20d (which was bigger than it needed to be for APS-C), but I would love to see it fit into a K20d body in hopes that we might one day see an underwater housing for both cameras.
As far as 35MP, it's really more than I think is needed. I'd much rather see a 24MP full frame with a 6µm pitch for lower shadow noise and a higher diffraction limit.
Any FF camera needs to include APS-C crop mode for sure, and like you say, it should have a default behavior with a manual override, and maybe an APS-H crop for lenses that don't quite make the FF image circle, or for when filling the frame just isn't feasible. I would also like to be able see the crop in the viewfinder. A sliding mask just behind the diopter is my idea for achiving this and that would also provide options for different aspect ratios, but even something as simple as frame lines on the focusing screen would work.
Everyone pretty much agrees that AF needs improvement. I think 3d tracking is very important for sport and wildlife shooters. I would add that the AF array should cover a larger area of the frame, when you look at the 645D's AF area it is the same size as the K5, and I don't mean proportionally, I mean in absolute terms. I don't see why they even bothered to put multiple points in when it only occupies the central 10% of the frame, it pretty much amounts to center point select. Ideally I'd like to see it cover about 80% of the frame in height and width.
As far as lenses go, I think you're right on the money with constant f/4 glass. High ISO performance has made f/2.8 lenses something of a specialty tool, as long as the f/4 glass is optimized for wide open shooting. There will be folks who just have to have f/2.8 (like me), but many more will be attracted to the lower price and smaller size of the slower lenses knowing that ISO 200 looks as good as ISO 50 did in the film days. Some may even decide to sell me their old FA* 300mm f/2.8 for a good price...