We have received a Pentax K-5 IIs and is running it through its paces for our in-depth review which we expect to publish very soon.
It soon became evident from our test shots that the AA-filterless K-5 IIs produces better image quality than the K-5/K-5 II (according to Pentax the K-5 and the K-5 II produce identical image quality so we used our old and trusted K-5 for the comparison).
Below is a 100% crop of a Caterpillar, but first we show the overall scene:
The lens was an smc Pentax FA* 85mm F1.4, set at F5.6. Shutter speed 1/500s, no EV correction, and all image parameters were as per the camera defaults. The photos were taken right after each other.
100% crops from the center of the frame:
Pentax K-5 IIs:
The image from the K-5 IIs is visibly cleaner and sharper.
So what about moire (false color patterns)? The K-5 IIs doesn't have an AA filter in front of the sensor so it should in theory be more susceptible to generating moire.
It is not a question of moire or no moire, though. It is a question of less or more. When shooting landscape, buildings and such outdoors we were unsuccessful in provoking moire. Shooting our test chart on the other hand brought out moire in K-5 images as well as in the K-5 IIs images, but significantly more pronounced in the latter case. Regarding contrast and resolution the K-5 IIs again came out well ahead of the K-5.
For this test we used an smc Pentax DA 35mm F2.8 Limited Macro lens set to F4 at ISO 100. Our upcoming review will provide samples at more ISOs and F-stops.
Pentax K-5 IIs:
So there you have it. Unless your work involves making photographs of objects (clothes, textiles, etc.) with fine repeating patterns you might want to consider the advantage in clarity and resolution which the AA filterless K-5 IIs can provide.