Originally posted by K David To my eye, the smaller MP sensors like on the K-5 and K-7 give lenses a smaller aperture at which diffraction softening becomes an issue. Also, the smaller-MP sensors are more forgiving to lenses meaning that more lenses deliver better results in a wider range of settings.
Also, a 16-MP sensor is cheaper, the file size is more manageable for people who don't own computers with Google Data Center-like processing capacities, and the files write faster so burst mode lasts longer. Also, with the exception of a small number of enthusiasts, stupid megapixel numbers don't add any value for users. MOST people who use a camera don't use more than 8MPs anyway -- evidenced by how many photos are taken with phones instead of high-dollar DSLRs. I'd actually be okay with my APS-C sensor being 12 or 14 MPs. I wouldn't even WANT to go beyond 18 or 20 for an FF camera.
No denying that the sensor specs are better for the K-3, but the 24MP file size has a number of drawbacks that actually hinder most users (even the users who don't realize they're being hindered.)
This does bring up a very good point that I totally forgot to mention.
True, most general photographers would be happy with 12-16 MP however I kinda feel like the intended audience of the K-3 is at least some part landscape photographers or adventure photographers who are happy to have as many megapixels as possible.
So at the very best, we can hope that a successor to the K-3 doesn't have MORE than 24 MP. However in the entire history of DSLRs I don't think a lineup has gone backwards in MP count. Maybe if you count the Canon 1Ds mk3 -> Canon 1DX but that is IMO a whole new class of camera.
Anyways, here is what I was going to say. One thing that I'd love to see on the K-3 is expanded DNG options. The DNG format is very versatile, and they could probably pull off a 16 MP or 12 MP capture mode with minimal loss of overall image quality.
On top of that, for example Nikon offers the option to switch back to 12-bit RAW capture, AND the option to turn on lossy compression for extremely high-volume gigs. I've been using this feature for many years as a Nikon wedding shooter who cranks out 100,000 images per year on 12-24 megapixel cameras, and it is a huge help. Sure, for landscapes or fine art or editorial you can use 14-bit lossless RAW, but if you're concerned about space then you can almost cut your filesize in half by using those other RAW options.
That, IMO, is the best that Pentax users can hope for. That they keep the sensor at 24 MP and add filesize options to the PEF format, and/or additional DNG options.
=Matt=
PS if it's diffraction you're worried about, rest assured that more MP is still not a bad thing. You could just down-size everything to 16 MP in ACR and still come out way ahead. Personally, I extensively shoot various 24 MP crop sensors (K-3 and three misc. Nikons with similar sensors) at apertures like f/8 and f/11 without diffraction getting too ugly. The lack of an AA filter really helps to maintain per-pixel detail. :-)