D2

Different file types can alter the size of files. For example, a JPG file reduces the quality of the file itself in order to make the file size smaller. This is the best way to conserve file size, but at the expense of quality. There are other types of files that also make the file size smaller, but no where near as much as JPG's, these are PSD and TIFF files. These don't alter the quality of the file at all, thus not really altering the file size much at all, but still a little bit. These are known as LOSSY file formats.

Graphic file compression programmes reduce file size by taking away pixels from images. This is an excellent way to reduce file size, however, you need to be careful because too much compression will lead to the distortion or pixelation of the image.

Image resolution is the size of the actual image itself, measured by DPI (dots per inch). For example, an image may be 500x350, meaning that for every inch of imagery, there are 500 vertical dots (pixels) and 350 horizontal dots (pixels). This is also how the quality of a TV screen is measured: A full HD TV is measured as 1920x1080 DPI, or 1080p. The file size and quality are parallel, meaning they go up and down together. The higher the resolution of the image (higher the quality), the bigger the file size.

Colour depth is the amount of colours used in an image. There are three main types of colour scheme, GS (Greyscale), RGB (Red, Green, Blue) and CMYK (Cyan, Magenta, Yellow and Black). Each colour scheme you go up in, the more colours can be made, obviously. For example, you can't have the colour red in an image that is using greyscale as it's colour scheme. And RGB can only cover red, green and blue, as well as the colours those three can make.