RAW: How Many Colors?

[cole]

This question has bugged me for a long while:

How many colors can a Canon DLSR capture and subsequently store in a RAW file?

For a 24-bit JPEG, it's straightforward enough-
2^24 = 16,777,216 or 16.8 million colors.

If a RAW file stores 32-bits of color information, that would be:
2^32 = 4,294,967,296 or 4.3 BILLION colors!

Some literature tells me that the RAW file is 48-bit. Now we all know that RAW contains more color information than a 24-bit JPEG, but if RAW stores 48-bits of colour information, that's
2^48 = 281,474,976,710,656 or 281,475 BILLION colors!!!
which I'm a little doubtful.

Anyone knows what the truth is?

[Dans_D60]

Canon RAW images are 12-bits per color channel or 36 bits total [RGB * 12]. Typical JPG files are 8-bits per channel or 24 bits total [RGB * 8]. Other formats can handle larger channel color depth including JPEG2000 (16-bits per color channel), TIFF (16 bits per color channel), and so on.
Dan
http://www.pettusphoto.com

[cole]

thanx Dan.

that means
2^36 = 68,719,476,736 or 68.7 BILLION colors?

wow.

how come nobody ever mentions that?

[Dans_D60]

It’s true when you integrate all the colors together the result will yield billions of color combinations. Nonetheless, the camera and application software handle each color channel separately (actually the sensor does not “see” color; 3 monochrome channels with pre RGB filters to resolve color). As you know, 12-bits of resolution results in 4,096 color-range for each color channel.
Dan
http://www.pettusphoto.com