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Old Oct 17, 2006, 5:25 AM   #1
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First, see the manual about the jpeg and RAW file size: http://www.pentaxforums.com/K10D_Manual.pdf

and also a review by Ken Rockwell on the Nikon D80:

Some facts:
1. a 512MB SD card stores 296 one-star Large 10MP jpeg files on the K10D. Thus, each file is 1.73 MB large;

2. a 512MB SD card stores 29 RAW files in PEF or DNG format for the K10D. Thus, each file is 17.66 MB large;

3. Each Pentax 12-bit RAW file had a large coarse (one-star) jpeg embedded and then the rest of the 12-bit data are packed as 8-bit byte. As such, the actual data size of the RAW data is merely 15.93 MB;

4. A Nikon D80 compressed NEF for "busy scene" (worst case, largest size) is only 9.2MB each.

Now, here comes WHY *compressed* RAW is very important and crucial!:-

1. A large 4GB SDHC card can store only 226 RAW images for the Pentax K10D. For the same card used, the Nikon D80 can hold up to 434 images. Do note that the resolution and number of bits are exactly the same, since both use the same sensor, i.e., 10 MP and 12-bit. The difference in ratio is 434/226 = 1.92 (nearly doubled/halved)!

2. That means that if a Pentax K10D user brings his DSLR for a just longer travelling, he needs to bring double the SD cards for double capacity;

3. Digital photography is all about digital storage. So, harddisk and/or DVD storage are all needed to be doubled! Say, when a 250GB harddisk is adequate, it will becomes 500GB. If two 250GB HDDs are needed, it becomes two 500GB and so on..

4. It is well known that the bottle neck for DSLRs in speed and continuous frame rate is on the memory card writing and reading speed (thus high speed memoery buffer in large size is required). Doubling the file size means doubling the write and read time from and to the SD(HC) card (interface)! If the same timing is to be kept, the speed/buffer size needed to be increased in double!

5. Compressing RAW need time but processor seems to handle this much faster than to read/write from/to memory card now. So, if the file size is very large, the DSLR's buffer must be increased and the memory buffer's speed must be made very high -> but the user benefits nothing for this even the hardware is more powerful, just because of the super large file size. Nikon seems has sucessfully managed to create a very fast DSLR with compressed RAW, i.e., the D80! The K10D is a slow camera in continuous shooting rate but indeed it has very powerful memory buffer: 800MHz DDR SDRAM!

6. From what Pentax insider says in rumours, the K10D will soon have the 16-bit RAW (as an option?). It's both a good news and bad news. The good news is that 16-bit RAW is the first in the world which may have a higher image quality for more number of shades, at least theoretically. The bad news is that the RAW file size of the UNCOMPRESSED Pentax RAW will then be 22.97* MB!! Thus, a 4GB latest SDHC card can store only up to 174 images!!

*22.97MB = 15.93MB / 12bit * 16bit + 1.73 MB

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