Originally posted by alanwm406 Thanks for all your comments.I was wondering what you meant by being surprised when comparing the RAW files K10/20 Alfisti. Is having a weak AA filter a good thing or a bad one?
I totally agree with Alfisti. Images coming from my K-7 only offer a little more resolution than those coming from my K10D when shooting RAW, and only when using excellent glass (my DA 16-45mm F/4 isn't up to the task on the K-7, while my Sigma 70mm F/2.8 Macro was quite capable).
A strong AA filter reduces the moiré and the jagged edges in diagonal lines coming from digital images, by "softening" these images a bit to avoid both effects.
So a weaker vertical AA filter results in sharper images, however with the side effects of more demosaicing artifacts, more moiré and more jagged edges in diagonal lines. Such artifacts are rarely visible unless you pixel-peep at 100% or you produce very large prints, however.
All that applies only if you shoot RAW, of course.
If you shoot in JPEG, the in-camera image processing can turn sharp images coming from a weak AA filter into soft images because of the image processing. The K10D is a good example of that. In RAW, it delivers sharp, crisp images, while in JPEG, the images always remain a bit soft even when in-camera sharpness is raised at the maximum.
But with careful RAW processing (especially at the sharpening phase), moiré and artifacts can be avoided while keeping high per-pixel detail.
That's one of the reasons why I always shoot RAW, unless I have no other choice.