Apple Aperture Digital Photography Fundamentals - Manual (Page 39)

Chapter 3 Understanding Resolution 39
Here’s a practical example of bit depth. To understand the effect of bit depth on an
image, look at the picture of the girl below, which is an 8-bit grayscale image. Her eye is
used to illustrate the effects that lower bit depths have on the resolution of the image.
Formats like JPEG use 24 bits per pixel: 8 bits for the red channel, 8 bits for the green
channel, and 8 bits for the blue channel. An 8-bit color channel can represent 256
possible values (2
8 ), while three 8-bit color channels can represent 16,777,216 values (2 24 ).
RAW image files also use three color channels. Because most RAW files have the capacity
to capture 12 to 14 bits per color channel, their range of colors is exponentially larger.
1 bit
2 possible values 2 bits
4 possible values 4 bits
16 possible values 8 bits
256 possible values