On Sat, Nov 18, 2006 at 01:11:05PM -0700, Joseph Tainter wrote: > How does one know that a compressed RAW file is actually lossless? > > Over at dpreview, Steve (apparently the first kid on the block with a > K10D) has posted a DNG file taken at ISO 1600 here: > > http://www.sendspace.com/file/zsdg52 > > It is a 6 mb file. When you open it in CS2, then resave it as a TIFF, it > becomes a 29 mb file. So clearly the DNG was compressed. > > I don't want to use RAW compression unless I cam be completely certain > that it is lossless. How does one know?
One further point - at present I believe the only way to get a compressed DNG is using software on your computer; the in-camera DNG is uncompressed. Pentax have added compression to PEF files (I'm sure this is lossless, too), but haven't yet got DNG compression in the firmware. I expect to see it at some future date, but I suspect they don't yet have a lossless JPEG library built for their embedded processor. Presumably they are using some other type of compression for the PEF files on the K10D. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
