Image Resolution, DPI & Color Guides

The difference between mixing light and mixing ink — and why a screen can show colours a printing press physically can't reproduce.

The single coloured square every digital image is built from — what one pixel actually stores, and why you can see them when you zoom in.

One counts the pixels in a digital image; the other counts the ink dots a printer lays down. They get used interchangeably, and here is when that is fine and when it will bite you.

The number behind 'true colour', the 256-colour ceiling on GIFs, and why a smooth sky sometimes turns into visible stripes.

The real amount of detail in an image, counted in pixels — and why it's a different thing from megapixels, DPI, and how big the picture looks on screen.

The reason a punchy photo sometimes turns dull the moment you post it online — a mismatch between the colours your file uses and the ones the web expects.

The shape of your image, independent of how big it is — and the reason something always gets cut when the shape doesn't match.

A fourth value on every pixel that says how see-through it is — and the reason a logo sometimes arrives with a white rectangle around it.

Your photos carry a hidden record of how, when, and sometimes exactly where they were taken.

A number people obsess over for screens, where it does nothing at all — and under-think for print, where it decides everything.