John, Leon ... It all depends on what you want to do with the final image.
TIFF and PSD are quite similar, although TIFF will work with programs other than PS. If you're saving your files with layers and other attributes, or in 16-bit, it's best to use a TIFF or PSD file. Large layered PSD files take up less disk space than the same file in TIFF. That's because (as I understand it) PS compresses the PSD files when saved. You'll see that straight, non layered files, are about the same size when using TIFF or PSD. A number of people on the PS User-to-User forum are leary of using compression when saving TIFF files. First, in some situations (as you've discovered) there's no space saving whatsoever. secondly, there's always the chance that something can get screwed up when saving and compressing a file and then decompressing it. It happens rarely, but it can, and has, happened. You've worked hard to get your final image, why risk damaging it. PNG won't save as a layered file, so if you intend to do further work on the file, or may just want to have an "original layered final" copy, you'll still need a TIFF or PSD. My workflow is such that I always save a PSD or TIFF with all the layers, alpha channels, and saved selections that were used in its creation. Shel > [Original Message] > From: Leon Mlakar > Photoshop lets you save the 16-bit per channel image in PNG? Which version? > I know 7.0 doesn't. > > Once you finished your processing (PSD preserves layers and other Photoshop > internal information) I don't see any disadvantages except that 16-bit PNG > is probably not as widely supported as TIFF. The advantage of PGN is very > good lossless compression that gives you smaller file of any other standard > format. For personal archive is a good choice. > > BTW, PNG is not Adobe's format. That's a public standard and acronym stands > for Portable Network Graphics format. > > Cheers, > > Leon > > >-----Original Message----- > >From: John Coyle [mailto:[EMAIL PROTECTED] > >Sent: Saturday, June 04, 2005 8:46 AM > >To: Pentax-Discuss > >Subject: PSD v TIF v PNG > > > >Does anyone know of any disadvantages in saving processed > >images in the Photoshop .PNG format? > >I just worked on an image I want to keep at the best possible > >quality, and compared the various file sizes as follows ( file > >is a 30cm x 20 cm 16-bit RGB image in sRGB): > >PSD file size is 303 MB > >TIF-ZIP file size is 285 MB > >TIF-NONE file size is 310 MB > >TIF-LZW file size is 379 MB > >PNG file size is 218 MB > > > >These are considerable variations in the volume of data > >stored: all saves after the first conversion from .PEF (saved > >as .PSD) were then taken from the .PSD file, and I am > >concerned that image degradation will be permanently saved! > >Although, of course, I can always go back to the .PEF file, > >and a print from the PNG file looks fine. > >All advice gratefully received - and followed! > > > >John Coyle > >Brisbane, Australia > > > >
