Color depth, also known as bit depth, refers to the number of bits used to store color information for each pixel in a digital image. Using more bits per pixel allows a greater range of possible colors. Color depth can be measured using the total number of bits used for a pixel (bits per pixel) or the number of bits for each RGB channel (bits per channel). Most digital images and computer monitors use 24-bit color, which supports 16.7 million possible colors.
Images and monitors that use a low color depth are limited in the range of colors they can show. For example, a single bit of color depth only provides two possible values for a pixel, resulting in a black-and-white image, while 4 bits of depth allow for 16 possible color values. Higher color depth allows a wider range of color information, but requires more data to store images and more bandwidth to send the video signal to the monitor.
Common Color Depths
Since 16 million colors are more than the human eye can distinguish, 24-bit color is considered good enough for general use. However, some formats and workflows use other color depths.
- 8-bit color saves each pixel using a single byte of data, displaying a maximum of 256 possible colors. Most 8-bit images use indexed color, which creates a palette of 256 colors out of a wider gamut. They also use dithering to blend colors together more smoothly. .GIF and low-color .PNG images use 8-bit color.
- 24-bit color is referred to as True Color. It uses 8 bits per RGB channel to display 16.7 million possible colors. Most computer monitors are limited to 24-bit color. Some image formats add an 8-bit alpha (transparency) channel to use 32 bits per pixel. Most digital images and HD videos use this depth.
- 30-bit color is referred to as Deep Color. It uses 10 bits per RGB channel to display more than 1 billion possible colors. This depth allows for higher contrast and increased luminance levels, which is important for high-end HDR monitors and UHD 4K televisions. Most 4K videos use this depth.
- High-end digital cameras can capture images at even greater color depths when taking RAW photos, providing photographers with extra image data for more-precise photo editing. Depending on the sensor, digital cameras can take RAW photos with 12, 14, or even 16 bits per channel (36 to 48 bits total).