> IIRC, the *istD not only does not compress RAW files, but also stores
> pixels in 16bits instead of 12, taking up 30% more space than necessary
> in the process.
>
Yes... quite a brain-dead move on Pentax's part.
> 10 Mpix should take 20 Mbytes if sampled at 16 bits, 16 Mbytes at 12bits
> (without the attached JPG preview). While lossless compression works
> quite well with 8 bit pictures, I've always had inefficient compression
> rates with 16bit images (I assume it gets harder to find two identical
> pixels to compress!).
>
> If the K10D produces 11MB 16bit files, this is almost 50% lossless
> compression, which would be pretty good indeed! Hopefully it's indeed 16bit.
>
That's not out of line to get 50%. My experience on using
general-purpose compression algorithms on my -DS RAW files is about 65-75%
of their original size at best (bzip2) to be about 7MB average after
compression. Given about a meg of that is incompressibly wasted the
full-sized embedded JPG, lossless compression can get them down to 6 MB
without trouble.
Canon's algorithm appears to be more optimized for images, because
a buddy's RebelXT averages about 7MB per 8 Mp frame.... that'd be a little
over 5 MB if it were 6 Mp..... pretty much inline with the 11MB/10Mp
claim.
-Cory
--
*************************************************************************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
*************************************************************************
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