Understanding Bit Depth

Each pixel in a digital image has a ëbit depth‰ or range of possible color values that represent it.

Possible ëBit Depths‰ and what they mean:

1 bit

Think of a bit as an on/off switch. It can be either off or on to create a different effect. In Computer terms this off or on is equivalent to a Zero or a One. So a bit can be either a 0 or a 1. In digital imaging this is equivalent to Black or white but with no greys between. On a scanner this is usually called line art

2 bit

2bits then combine to give you 4 valuses: 00 10 01 11 This would be black/white and two grey values but is not a conventionally used bit depth.

8 bit (greyscale)

This is your typical bit depth for a greyscale image. It contains 28 or 256 values of grey.

8 bit (24 bit color)

RGB stands for Red, Green, Blue and uses three color ‹channelsŠ that are blended together to create a color image. Each channel has 8bits of information so 256 values per channel. Combine the channels together and you get 24bit color with 224 or some 16million possible colors. This is your typical bit depth for a color image.

16 bit (16 bit greyscale or 42 bit color)

This is used by some scanners and is an option within Adobe Photoshop for very high-quality images. The resulting file sizes are twice the size of an 8bit per channel image.