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Old Oct 27, 2003, 5:06 AM   #11
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Originally Posted by slipe
An 8 bit pixel is simply a series of three 8 digit binary codes. 8 binary digits can have 156 possible values in 10base, so there are 156 possible values for red, green and blue. 156 X 156 X 156 gives 3,796,416 possible colors from an 8 bit pixel. The full image file has other information about the relative position of the pixels, compression or decoding information, layers, the size the file would print at etc. But the pixels are simply code that represents a color.
156 should be corrected to 256 (and 256 x 256 x 256 = 16,777,216). Also I would not call this an 8bit pixel, it is 24bit.

The only reason to refer to an n-bit pixel is so you know the range of different values a pixel can have without knowing anything else about the sensor. Therefore it does not make much sense to refer to an 8bit pixel in case of 3 x 8 bits (8 bits per channel).
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Old Oct 27, 2003, 5:10 PM   #12
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156 should be corrected to 256 (and 256 x 256 x 256 = 16,777,216).
I shouldn’t post late at night. I just put 156 rather than 256 in the calculator window and didn’t pick up the error – thanks for the correction.

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Also I would not call this an 8bit pixel, it is 24bit.
Convention. My scanner and camera software refer to 24bit and 48bit files where Photoshop uses 8bit and 16bit. Photoshop seems to refer to the individual channel where most consumer stuff combines them. I don’t know why they refer to 8 and 16 bit images. But I know Photoshop will take only the two so a 12 (or 36) bit image has to be converted to 16 bits for Photoshop or you lose everything over 8. So I try to think in Photoshop terms.
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