I just discovered a self sensor test ( very accurate ) now build into KX,K7,K5 ( not Q ) , it is in MENU ( Setup Option 4) called " Dust Alert" , takes virtual picture of your sensor with all stains very visible ( highlighted ) , it is only enabled with later lenses attached to the camera .
the file on your SD card is called : DUST.JPG
you can download it onto your Mac/PC and view it on the big screen.
So... was it always there and I just did not see it?
No one never ever mentioned it on any Pentax forums, out of focus blue sky F22 was always recommended.
Did it possibly sneak in with past firmare upgrade?

It is VERY convenient!