Key Difference: 8 bit and 16 bit color describe two different types of graphics mode in which the image formation is stored in a computer’s memory or an image file. In an 8 bit mode, each pixel is denoted by one 8 bit byte. On the other hand, in a 16 bit color mode, each pixel is denoted by two bytes.

Digital images are colored by the combination of three primary colors of light. These colors are red, green and blue. The combination of these three colors generates billions of colors. In eight bit color graphics each pixel is represented or depicted by using an 8 bit byte. It can be expressed as  "2 to the exponent 8", or "2 x 2 x 2 x 2 x 2 x 2 x 2 x 2", which gives the number 256.

Thus, it contains 256 tonal values. It means that 256 shades of red, 256 shades of green and 256 shades of blue are available in 8 bit color mode. The combination of all these shades means 16.8 million possible colors. In eight bit color, 3 bits for red and 3 bits for green are assigned. Rest of the bits (2 bits) are used for the blue component.

On the other hand, in sixteen bit color graphics each pixel is represented or depicted by using a sixteen bit byte. It can be expressed by the expression “2 to the exponent 16”. This is equivalent to 65,536. It would also refer to 65536 shades of green, 65536 shades of red and similarly 65536 shades of blue. This has the possibility of generating 281 trillion colors.

In sixteen bit color, 5 bits are used for red, 6 bits for green, and 5 bits for blue component. This color mode gives many advantages over the 8 bit color mode. For example - it ensures smooth gradation of tone and color. It retains this feature even on making adjustments like contrast, etc. On the other hand, the file of the size becomes greater by using a 16 bit color mode.

Comparison between 8 bit and 16 bit color:

Images Courtesy: morphoinc.com