Thanks John ....'tween you and Godfrey I've learned a lot this morning. Time for lunch and to explore some DNG conversion options ;-))
Shel "You meet the nicest people with a Pentax" > [Original Message] > From: John Francis > > > When converting PEF files to DNG, the converted file is roughly 50% of the > > original. That suggests that some, perhaps a lot, of information in the > > original file is discarded. What's lost? > > Nothing. The DNG retains *all* the information in the PEF, as long as > you select the option to preserve an unmodified copy of the MakerNote tag. > Without that you'll lose any metadata that's not in standard EXIF tags. > I'm only aware of a couple of examples that most people might care about - > a code identifying the actual lens in use (if known), and the cumulative > frame count. Mind you, even if you do preserve the information, there > isn't any software I know of at present that can display the saved values. > > > When working with DNG and PEF files, and converting them to PSD or TIFF > > files after going through the RAW converter, the file sizes (for DNG and > > PEF "originals") are about the same size, and I see no difference in the > > results obtained from either format. How is it that the DNG, which is > > about 1/2 the size of a PEF, and the PEF, yield similar sized files when > > converted? > > DNG has good compression algorithms. > As far as the image pixels are concerned, the results should be bit-for-bit > identical between conversions from the DNG files and from the original PEFs. > > > All this suggests that the PEF, and I suppose other RAW format files, > > contain a lot of unnecessary information. Given that the results from a > > PEF and a DNG file are identical, is there really any reason to save the > > PEF file? > > Given the cheapness of writable media (under 5c per gigabyte), is there > really any reason *not* to save the original? While the Pentax software > isn't really much good for RAW image conversion, it is the only program > that knows how to show the lens description. As it doesn't handle DNGs, > your better off saving a file in the format it expects. > > Once you've saved those archive copies, though, you might as well convert > to DNG for working images. I keep promising I'm going to get round to > doing that to save space (the size differences for a D are even greater > than for a DS). I'd recommend: > > o Save copies of the files from the camera (PEFs, JPGs, etc.) > to backup media immediately after copying to your hard drive > (and before deleting the images from your SD cards). > I try never to have an image in only one place, except for > the unavoidable times after expusure and before downloading. > > o Convert to DNG (this is a good time to systematically rename files) > > o Save another copy of everything (to a second hard drive, > and to write-once media).
