Why we ask for 4000 pixels on the long edge
The minimum size for contributors was not picked at random. Here is the arithmetic behind it.
Warm and cool: reading a palette from a photograph
How to pick three colours from a photo and keep a layout calm, with a worked example.
JPEG, WebP or TIFF: what to ask for and when
A short guide to the three file types our customers ask about most, and what each costs in size and flexibility.