>From what I've read, I think many people have a
misconception of what RAW really is. I do not believe
that a Canon RAW file is simply a recording of the
luminance info from each individual pixel. I've read
(and I can't remember where at the moment, but if I
can track it down I'll repost) that Canon's raw format
is essentially a compressed (lossless) TIFF file with
some additional proprietary information (primarily to
carry the EXIF data and parameter settings used during
the shot), and an embedded jpeg for display on the
LCD. (Even the 20D, which writes a separate JPG file
in RAW+JPG mode, still has an embedded jpg within the
raw file.) In fact, some of Canon's earlier digital
SLRs used the extension .TIF on their raw files.
The camera is already doing plenty of processing to
create the raw file. The key difference is that it is
NOT throwing data away, as it does when recording a
jpg. The image is saved as the full 36 bits, it's not
compressed, and shooting parameters (sharpness,
contrast, saturation, etc.) are simply recorded along
with the data, rather than being applied to the data.
It is my understanding that Nikon's raw format is
essentially a modified TIFF as well, as is Adobe's
DNG. If this is true, then it shouldn't be that big a
deal for Canon, Nikon and other's to modify their
cameras to write .DNG files.
As long as the standard leaves enough room for growth
(e.g. true 16 bit data instead of 12 bit, plenty of
extra room for future tags) it shouldn't be necessary
to replace it a few years down the road.
Some have expressed concern about long term support of
this format. This begs a question: how good is Adobe
at supporting old formats. Can I use PSCS to open a
file created in Adobe 3.0 without information loss?
If so, then I think I trust Adobe to offer long term
support of DNG better than I trust Canon to offer long
term support of all of its ever changing RAW file
formats.
Another factor working in DNGs favor in the long term
is that Adobe has released the spec into the public
domain. Anyone can create a program that reads/writes
DNG files without paying royalties, I believe. If
multiple manufacturers use DNG as their raw file, that
will attract many software vendors to support it. The
more vendors that support it, the better the
likelihood that it will continue to be supported into
the future. TIFF has been around for many years, but
because it is a widely used standard, and supported by
every graphics program under the sun, I think it will
continue to be supported over the long term.
Obsolesance is a worry with any digital information
storage. Assuming I don't go blind, I can always get
data off of a negative, transparency or print. Getting
data out of digital file, whether it be an image or a
word processing document, is less assured. (Got any
old "Electric Pencil" files from an Apple II lying
around?).
If anything, though, that's an argument against
shooting digital at all. I'm actually more worried
about being able to read the physical storage medium
in 10 or 20 years. Got any data that you wrote onto
5.25" floppies? Got a computer that will still read
it? Will you be able to get a computer with a CD-ROM
drive in 20 years? What will you do with all the
images you've archived to CD-ROM, or to DVD, when all
computers come with 1000 Terabyte holographic data
stores, and CDs are something you might see in a
display at the rock and roll hall of fame?
=====
Bob Meyer
I don't suffer from insanity... I enjoy every minute of it.
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