Understanding Bit Depth

In digital photography the expression 'bit depth' relates to the number of different tones or colour that can be represented by the pixels. These tones are also known as levels.

JPEG images are 8-bit files which means they are 28 (2 to power of 8 or (2 x 2 x 2 x 2 x 2 x 2 x 2 x 2) indicating that they have a bit depth of 256 possible colours. So, one pixel of a JPEG file can represent 256 different tones or colours.

FIG. 1.34 8-bit example.

With a 16-bit file you have an enormous 65,536 shades in each of the channels, so smoother tonal graduations are possible and more colours can be displayed.

With the exception of a few high-end models, most SLRs are 12-bit files, so a RAW image will record 212 or 4096 possible colours.

So, one pixel of a RAW image can signify 4096 different tones or levels.

FIG. 1.35 16-bit example.

FIG. 1.35 16-bit example.

A disadvantage of shooting a JPEG file is that several thousands of tones available to us end up being immediately discarded due to in-camera processing with JPEG.

This simply means that the higher the bit depth, the smoother and more continuous the tonal graduation will appear in a digital image.

Scientific research has shown that only 200 tones are required for humans to believe they are looking at a continuous tone photo-quality image.

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100 Photography Tips

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