Color depth

Color depth, is the term used to refer to the number of bits used in a single pixel on a screen [1], it is also reffered to as bit depth or bits per pixel (bpp). The number of colors increase exponentially depending on the number of bits, eg. a 2-bit image will have 4 colors, an 8-bit image will have 256 colors and so on and so forth. Images displayed in 16-bits are known as hi-color images, and images of 24-bits (around 16.7 million colors) are usually reffered to as true-color display, due to the accuracy of the image to the human eye (which is said to only be able to differentiate between 10 million colors [2]). Images may be displayed in 32-bits but this will only be visible to experts [3]. It is important to note that the color depth is a setting that can be adjusted through the operating system, which indicates the maximum level of color depth a computer supports. Thus, if you send a 24-bit image to an 8-bit computer screen, you will view the image in 8-bits. The level of color depth depends on the video memory available [4]. Most computers support 24-bit displays. The colors we view on an HDMI display have 30-bits, 36 bits, and 40-bits [5].

1-bit image

2-bit image

8-bit image

24-bit image

Understanding Color in Computers

Colors on screen are represented differently than in pigment. In pigment the primary colors are red, blue and yellow, which when combined create the color black. This is known as subtractive color because colors are moving from white to black. Another subtractive color method often used in printing is CMYK (Ceylon, Magenta, Yellow, and Black).

On a screen colors are represented by additive color, meaning the screen start black, and when the primary colors are mixed together we get white. The primary colors in additive color are red, blue, and green (RGB). This is particularly important in the fields of graphic design, and photography where they have to consider rendering images on screen for a final printed product.

The quality of an image usually depends on color depth and resolution (the number of pixels on a screen). Images with a large number of pixels, each having a high color depth allows for better looking images.