Originally posted by Just1MoreDave My guess is that it's because K-7 bits are 12-bit.
12 bits is 4096 levels (0 to 4095). On a well exposed continuous tone image there should on average be some pixels at all of these levels. It would appear that there is some dodgy scaling being done after the K-7 (Samsung sensor) analog to digital converter, the effect of which is that some counts (recorded intensity levels) can't occur. On my K-7 it is every 7th or 8th count, on earlier K-7s it could be as bad as every 4th or 5th count.
On the K-5 a different approach is used, without such scaling but with an offset from zero.
All this will not make much difference at medium/high intensity levels, once the data had been gamma corrected and demosaiced. However at low intensity levels and at high ISO after scaling and demosaicing the missing counts will result in an apparent increase in image noise.