It appears that yesterday, I was guilty of the common mental error of believing what I wanted to believe. I like the idea of Adobe DNG (digital negative)—a vendor-independent raw standard that works across platforms and promises unlimited future support. The DNGs I was shooting with the K20D were opening up in my older copy of Photoshop, and they looked great.
But appearances can be deceiving. Go into ACR (Adobe Camera Raw) and look at the numbers in the "White Balance" box, and you'll notice they can be way screwy—on my DNGs, temperature was 7000 Kelvin for one picture and tint was +97 for another, in fairly neutral light. That's not right. Carl tells me that's because the LUTs (lookup tables) are not proper for the camera and the raw file is not being unpacked properly. He wrote about this last year in his series of posts on the K10D, when he noticed the raw files didn't behave right until he got a version of ACR in which the K10D was supported.
So, even if you're using DNG, it's still necessary to use a version of ACR (or whatever raw converter you choose) that specifically supports the K20D (or whatever camera you own). With Adobe products, you need ACR 4.4 or Lightroom 1.4 to get K20D support. ACR 4.4.1, the latest version, is not compatible with versions of Photoshop prior to CS3, although it is usable with updated copies of Lightroom and with Photoshop Elements later than version 4.0 for Macintosh and 5.0 for Windows.
Carl is currently shooting PEFs (that's Pentax's proprietary raw file type) because they're smaller files, then immediately converting them to DNG using Adobe DNG Converter, which is a free download.
Mike (Thanks to Carl for setting me straight)