Layers

A layer is like a sheet of transparent paper: part of the picture lies on it, and the layers stacked together make one whole picture. Each layer can be edited separately without touching the others, which is why so much of PhotoShop's power is in layers: a new picture, text or a cut-out part usually lands on a new layer automatically, and in current versions there can be hundreds of layers. In the Layers palette (Window → Layers or F7) every layer has an eye icon (show/hide), Opacity (0–100%), lock, link, style (fx), mask, adjustment layer, group, new-layer and delete buttons. A layer higher up covers those below it, and dragging a layer with the mouse changes the order. The bottom Background layer is partly locked: its position cannot be changed, but double-clicking it turns it into an ordinary layer. A mask hides part of a layer without deleting it: white shows, black hides, so a mistake is easy to correct. An adjustment layer changes colour and brightness without touching the original pixels. When there are many layers they can be put into a group and controlled like one layer; Ctrl+E (Merge Down) merges a layer with the one below. If a layered work is saved as PSD the layers are kept; exported to JPEG or PNG the picture becomes flat.