Originally posted by robgo2 Over at the other Pentax forum, GordonBGood has stated that the K-7 actually has limited DR at low ISO, because of shadow noise. This makes it more difficult to open shadows aggressively without bringing forth a lot of noise. The K-x and the Nikon D300s seem to be better in this regard.
Shadow noise affects DR testing procedures that use a noise threshold (i.e. Imatest). DPreview tests off of in camera JPEGs, so the amount of noise reduction directly affects the tested DR. If you look at the "ACR best" DR results from a converted RAW image, you'll notice the K-7(10.5EV) is right with the D300S(10.1EV) and 7D(9.8EV).
You should lose about 1 stop of DR for every stop you raise the ISO above the sensor's native setting. So, the tests that show the DR practically even across the ISO range seem somewhat questionable. Notice also on the ISO noise testing at DPreview, the 7D and D300S both show their noise output triple from the JPG to RAW comparison, while the K-7 stays pretty much even. Don't get me wrong, the K-7 does, for whatever reason, produce more noise in the blacks than the other cameras. However, up to ISO1600, the amount of chroma noise is nearly identical to the 7D and D300S.
In any event, posting anecdotal information obtained from synthetic image benchmarks to refute real-world success is kind of weak.