See what Peter Zheng has lately found and reported:-http://tech.groups.yahoo.com/group/ricehigh_pentax/message/937Reports from K-7 users about sensor stains with photos clearly showing those are posted. And yes, the symptom is exactly the same as the previous K-5's.So, it is almost safe to conclude that it's Pentax' AA filter that causes the problem! (Source Thread: http://bbs.kakaku.com/bbs/
