Apple Aperture Digital Photography Fundamentals - Manual (Page 38)

38 Chapter 3 Understanding Resolution
Learning About Bit Depth
Bit depth describes the number of tonal values or shades of a color each channel in a
pixel is capable of displaying. Increasing the bit depth of color channels in an image’s
pixels exponentially increases the number of colors each pixel can express.
The initial bit depth of an image is controlled by your camera. Many cameras offer
several file settings; for example, DSLR cameras usually have two settings, allowing the
photographer to shoot an 8-bit JPEG file (with 8 bits per color channel) or a 16-bit RAW
image file (with 12 to 14 bits per color channel).
Image file types use static bit depths. JPEG, RAW, and TIFF all have different bit depths.
As you can see in the table below, the file type you shoot your images in dramatically
impacts the tones visible in your images.
Note: The bit depth of an image file is uniform (each pixel in the image has the same
number of bits) and is initially determined according to how the image was captured.
Bit depth per color channel
Possible tonal values
per color channel
Nearest equivalent file type
2 4
4 16
8 256 JPEG, some TIFF
12 4096 Most RAW
14 16,384 Some RAW
16 65,536 Some TIFF