What does "colour depth" refer to in terms of images?

"Colour depth" refers to the number of colours used in an image. It is expressed in bits, with each pixel in the image capable of representing a certain number of different colours based on its depth. For example, a colour depth of 8 bits allows for 256 different colours, while 24 bits can represent over 16 million colours. This aspect is crucial because it determines the richness and quality of the image. A higher colour depth allows for smoother gradients and more accurate reproductions of images, contributing to a more visually appealing result.

While resolution, file size, and image format are important characteristics of images, they do not describe colour depth itself. Resolution refers to the number of pixels in the image, file size is related to the total amount of data stored, and format pertains to the specific encoding or structure used to save the image data. Each of these elements has its significance, but they do not specifically address the concept of colour depth.