Without an anti-aliasing filter anyway....two DSLRs, a number of other assorted cameras such as the Leica and the Pentax Q, most if not all medium format digital cameras....manufacturers are starting to ditch the AA filter. The quest is for greater detail and the AA filter is there to blur detail.
Why? To avoid interference effects that we call moire. The same effect that used to cause newsreaders' herring-bone jackets to shimmer on TV. But remove the filter and we get much better detail, but have sensors moved on so much that the risk of moire is now more theoretical than practical?
In the field of DSLRs Nikon were the first in with their variant on the D800, the D800E. Noe Pentax have followed suit and the K-5 II has been closely followed by the K-5 IIs. I tested the K-5 II for EPZ in November and repeated the exercise for the K-5 IIs variant in the last week or so. As far as possible, for the shoots were separated by two months, I repeated the original images. As soon as I examined them on the screen I knew that the IIs offered much better detail resolution. Masses of interlocking branches were delineated clearly rather than as a mush, hair was incredibly finely differentiated, the answer was clear.
Sensor technology has clearly moved on to a point where for most purposes the AA filter can be ditched. I can see why Nikon and Pentax elected to offer an option though, as not everyone is ready to accept the conclusion that resolution is siginificantly improved. I guess, to be fair, "significantly" is in the eye (literally) of the beholder, so my significantly might be someone else's not worth the candle, never mind another £130.00.
But I can onlt speak for myself, and there are plenty of others who seem to agree. So, thank you Pentax (I think) for offering me a better product, now I just need to engineer an excuse to spend the cash on a brand new K-5 IIs. I might not be able to do it straight away, but it's now firmly on the list. Oh yes, along with a nice all-black MX-1, although I confess that this latter choice is purely because I want one, not because I need one.
There's nothing wrong with wanting a new camera. Is there?