On Mon, Oct 31, 2005 at 09:35:32AM -0800, Shel Belinkoff wrote:
> 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).
