I looked into this a fair bit about 2 months ago by rummaging through some RAW files with a hex editor/tiffdumper. Basically, the .PEF files from a DS are TIFF-formatted files. Tiff is a more generic "container" file format than simply a single, flat image. Anyway, there are three different low-quality JPEGs embedded in it (160x120, 640x480, 3008x2004 or thereabouts). The largest JPEG is roughly 1MB in size.He also says that RAW does not compress losslessly. I knew this was the case for the -D but thought itwas fixed for the -Ds. Am I wrong as usual/expected?
The RAW image is stored as a 12-bit, uncompressed image. It's flagged as "Packbits," although strictly speaking, that's not correct. Packbits in TIFF-land refers to a type of lossless compression (RLE), but Pentax abused the tiff standard by calling 12-bits "packed." Fair enough, since TIFF format does not support a 12-bit density... 8/16, but not 12. Anyway, the sequential chunks of 12-bit data are packed together, whereas as far as I understand it, the -D padded the 12-bits off the A/D with four zeros to make it a true 16-bit TIFF. It's also horribly space-inefficient, of course. Although there's no lossless compression on the -DS, at least it doesn't waste a bunch of space storing zeros.
I actually contacted Pentax about a possible firmware update to include lossless compression, and the ability to NOT waste ~1MB on a low-quality full-sized JPEG but rather, a RAW+JPEG option with a full-quality JPEG. I got the usual, "Sounds like a good idea, but we're not going to do it" response. Maybe the next model will.
Probably more info than you wanted, but I'm pretty sure it's correct.
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
