At 04:06 AM 21/10/01 -0600, Bill wrote: >... >o The JPEG standard includes a lossless setting. Photoshop 6 supports it: >set the quality level to 12. it will compress to, say, 1/3 of the original >size. JPEG only supports 24-bit images.
G'day Bill. I had never heard of a lossless JPG, so I checked the JPEG FAQ, which basically says that there *was* an early version of a lossless JPEG, but it never took off. They also referred to a new standard called JPEG-LS - is this what you meant? I couldn't see anything about it in the PS Help file, but I only took a quick look. I would be most interested if PS6 really does supprt a lossless JPG.. As far as I knew, the main players were/are: TIFF - 48-bit, lossless, large files TIFF with LZ compression - As above but files can be much smaller (esp if image is not grainy or detailed), eg typically 1/2 to 1/5 original size JPEG - 24-bit, lossy but adjustable. File sizes often less than 1/5 of the uncompressed TIFF (depending on quality setting and image content) PNG - 24-bit, lossless. File sizes usually a bit smaller than compressed TIFF, but not as small as JPEG. (PNG's are also readable by most browsers, which makes them useful for 'critical' web-display.) FWIW, I always use TIFF without compression if in any doubt (I have had quite a few problems with lack of portability of LZ'd TIFs), and I am now moving over to PNG's for my own file storage in order to save CD space. The lack of 48-bit quality hasn't yet been an issue for me.. mt
