With the 10D, writing RAW format with the camera set to its defaults, I obtain 127 RAW files per a 1G CF card. If I modify the defaults with a custom function and minimize the embedded JPEG file, I can get 143 RAW exposures per 1G card.I've corresponded with someone at Pentax and told them they should enable/disable the RAW+JPEG function. Basically, either remove the full-sized JPEG embedded in the -DS RAW, or make it high enough quality to be useful. As it is, it's roughly 1MB... low enough quality to be fairly useless, but large enough to waste 15% of the space of the file.
The *only* variable in how large the -DS RAW files are is how well the three embedded JPEGs compress. The RAW data itself is uncompressed (although packed), 12-bit Bayer data.With the *ist DS, I get 100-105 RAW format exposures on a 1G SD card.
So the Canon will store 27-43% more RAW exposures per 1G card. While this is a useful improvement in space efficiency, I don't really consider that significant. Yeah, sure, I need 3 1G SD cards for the DS compared to 2 1G CF cards for the 10D, but they're cheap enough as to not be that much of a burden nowadays. I don't often need more than one 1G card anyway, unless I'm traveling.Aside from a bit of computational issues, there's no reason not to compress the RAW data. There could even be a "compress all now" you could use to "pack" the files on the flash card and make more room if it was too slow to do on the fly. Unlikely, though, given how slow flash memory is. It'd probably be faster to compress on the fly and spool to the card than to just spool the uncompressed onto the card. I think Pentax was just a bit behind on the design schedule and had to let something slip... sorta like USB-2.0 lacking on the -D.
Just for a datapoint, I took 25 -DS RAW files and compressed them losslessly with a couple of different methods:
249355733 bytes uncompressed (Full size, 9.5MB avg) 209182171 bytes compressed with 'gzip' (84% original size, 8.0MB avg) 209185296 bytes compressed with 'zip' (84% original size, 8.0MB avg) 158154181 bytes compressed with 'bzip2' (63% original size, 6.0MB avg)
A few of those pictures probably compress a bit better than most, since they were pictures taken out of my airplane (lots of sky, clouds, haze). Even with that, they could certainly be compressed to roughly 1MB/Mpixel, but it would take firmware work, and winders/mac software work.
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
