The Five Types of Masks in Photoshop

When you're creating and editing visuals in Adobe Photoshop, the image areas you hide make as important a contribution to the work you create as do the image areas you present. Experienced Photoshop artists know that rather than delete pixel information they don't want visible, it's better to use a mask, giving yourself the option to reveal parts of your image you first decided to hide. Photoshop's masks come in various types, each suited to a different image-creation task.

Layer Mask

In 1994, Adobe Photoshop 3 saved graphic artists from the tedium of maintaining separate documents to create multiple versions of an image. With Photoshop 3's new layers, artists could create composite images with discrete graphic elements, applying layer masks to hide or show all or parts of them. A layer mask consists of a grayscale bitmap. You can paint a mask by hand or use a selection to define its shape, and turn its visibility on and off by Shift-clicking on its icon in the Layers panel to view your image layer with or without its effect.

Vector Mask

Along with or instead of a layer mask, each Adobe Photoshop pixel-based layer can carry a vector mask that limits the visible parts of the layer through a vector clipping path. This technology entered Photoshop's roster of capabilities in 2002 with the release of Photoshop 7. Unlike traditional pixel-based layer masks, which can be soft, blurred or partially transparent, vector masks always define a fully opaque visible area bounded by a hard edge. You can turn vector masks' visibility on and off in the Layers panel the same way you turn off layer masks. If you turn a vector mask into a layer mask, it replaces an existing layer mask or adds one to a layer that doesn't include one.

Quick Mask

Adobe Photoshop's Quick Mask appears as an entry in the Channels panel rather than a layer-specific addition to a document. Capable of being edited just like a layer mask, a Quick Mask provides a temporary pixel-based visualization of a selection, one that improves on the animated dotted line called "marching ants" that appears in the document window. The Quick Mask shows partially selected areas in complete detail, whereas the marching ants only show the outlines of fully selected areas. A Photoshop document can't contain more than one Quick Mask, though you can save the selection it represents as an alpha channel or turn it into a layer mask. Quick Masks predate layer masks in Photoshop's history, going back to Photoshop 2 in 1991.

Adjustment Layer Mask

Identical to image-layer masks in every respect except the layer type to which they're applied, adjustment layer masks define which image areas are and aren't affected by an individual adjustment, including Levels, Curves, Hue/Saturation, Selective Color, and the rest of Photoshop's non-destructive correction layers. These pixel-based masks extend the functionality of adjustment layers, making it possible to create a narrowly specific color correction that applies to an equally narrowly defined portion of a layer.

Clipping Mask

Any Adobe Photoshop mask can serve as a clipping mask. The technology allows a layer mask or vector mask to apply not only to the base layer on which it's saved, but to any layer above the base in the image's layer stack. Designate a mask as a clipping mask by holding down the "Alt" key (Windows) or "Option" key (Mac), and clicking on the dividing line between the base layer and the one above it in the Layers panel.