Digital images are made up of tiny squares called pixels (picture elements). Each pixel has a colour value stored in binary. The more pixels and the more bits per pixel, the higher quality the image — but also the larger the file size.
Key points
Definition:Pixel: a single point (tiny square) in a digital image, each with a colour value stored in binary.
Definition:Resolution: the total number of pixels in an image, calculated as width (px) x height (px). Higher resolution = more pixels = more detail.
Definition:Colour Depth: the number of bits used to represent the colour of EACH pixel. More bits = more possible colours.
A colour depth of 1 bit = 2 colours (2^1). A colour depth of 8 bits = 256 colours (2^8). 24 bits = over 16 million colours.
Exam Tip:Higher resolution and higher colour depth both increase image quality AND file size.