Originally posted by Steve.Ledger Interesting, where is this information?
Um, there were some threads about this back when the K-01 came out and people compared it against the K-5.
The K-01 sensor is "the same" 16MP as K-5, K-5II, K-5IIs, K-30, K-50, K-500. But the K-5IIs doesn't have an AA filter (also called low pass filter). To my knowledge, the K-01 either has a weaker AA filter or is missing it altogether (I think the official sources were vague). I think the K-01 was sort of an experiment, Pentax seeing if they could get away without an AA filter and how it would affect live view and CD AF. The test worked, so they issued the K-5IIs, which became incredibly popular, outshining the other K-5 series. These days, many brands are experimenting AA-less sensors, but usually only high MP cameras (because at low MP, you need it)
Primary colour filter is another thing, which has to do with the bayer configuration. All colour CMOS-type sensors have this, which includes most cameras on the market. Notable exceptions are the Sigma foveon-sensor cameras and the Leica Monokrom. Digital sensors have a couple filters on there.