When downloaded straight from the camera digital photographs are flat files with all the picture parts contained in a single document, but Photoshop also contains the ability to use layers with your pictures. This feature releases your images from having to keep all their information in a flat file.

Different image parts, added text and certain enhancement tasks can all be kept on separate layers. The layers are kept in a stack and the image you see on screen in the work area is a composite of all the layers.

Sound confusing? Well try imagining, for example, that each of the image parts of a simple portrait photograph is stored on separate plastic sheets. These are your layers. The background sits at the bottom. The portrait is laid on top of the background and the text is placed on top. When viewed from above the solid part of each layer obscures the picture beneath. Whilst the picture parts are based on separate layers they can be moved, edited or enhanced independently of each other.

When layered files are saved in the PSD or Photoshop file format all the layers will be preserved and present the next time the file is opened. Photoshop supports the following layer types:

Image layers – This is the most basic and common layer type and contains any picture parts or image details. Background is a special type of image layer (3).

Text layers – Designed solely for text, these layers allow the user to edit and enhance the text after the layer has been made (1). They are vector-based layers and must be simplified (rasterized) to apply a filter or to paint on.

Adjustment layers – These layers alter the layers that are arranged below them in the stack. They act as a filter through which the lower layers are viewed (2). You can use adjustment layers to perform many of the enhancement tasks that you would normally apply directly to an image layer without changing the image itself.

Fill layers – Users can also apply a Solid Color, Gradient or Pattern to an image as a separate layer. These three selections are available as a separate item (Layer > New Fill Layer) under the Layer menu or grouped with the adjustment layer options via the quick button at the bottom of the Layers palette.

Smart Object layers – A Smart Object layer is a special layer that encapsulates another picture (either vector or pixel based). As the original picture content is always maintained any editing actions, such as transforms or filtering, that are applied to a Smart Object layer are non-destructive.

3D layers (Extended only) – Photoshop CS3/ CS4 Extended also has the ability to open and work with 3D architectural or design files.

Shape layers – Drawing with any of the shape tools creates a new vector-based shape layer. The layer contains a thumbnail for the shape as well as the color of the layer.

Background layers – An image can only have one background layer. It is the bottommost layer in the stack. No other layers can be moved beneath this layer and you cannot adjust this layer’s opacity or its blending mode (4).

By default Photoshop classifies a newly downloaded picture as a background layer. You can add extra ‘empty’ layers to your picture by clicking the New Layer button at the bottom of the Layers palette. The new layer is positioned above your currently selected layer. Actions, such as adding text with the Type tool, automatically create a New Layer for the content. When selecting, copying and pasting image parts, Photoshop also creates a new layer for the copied portion of the picture.

Version: CS2, CS3, CS4

The way that layers are linked changed with the release of Photoshop CS2.

In previous versions of Photoshop layers were linked by clicking in the link box on the left of the layer but now linking several layers is a simple matter of multi-selecting the candidate layers and then pressing the Link button (1) at the bottom of the Layers palette.

A Link or Chain icon is then displayed on the right of the individual layers that are linked together (2).

Once layers are linked the relationship of the content of each layer is fixed and all picture parts move together when one layer is repositioned.

To unlink a group of layers select any layer in the linked set and click on the Link button at the bottom of the Layers palette.

Version: CS2, CS3, CS4

In CS2, CS3 and CS4 layers can be more easily grouped, moved and managed than in previous releases of the program. It is now possible to multi-select layers inside the Layers palette using the same keystrokes employed for selecting thumbnails in Bridge.

Select a group of layers – Click on the top-most layer and then hold down the Shift key and click on the bottom-most layer in the group. All layers between these layers and the layers themselves will be selected (1).

Select individual layers – Select the first layer and hold down the Control key (Command – Mac) and select the other individual layers (2).

In addition to selecting layers in the Layers palette you can also select groups of layers that combine to make up an image part by dragging a Move tool marquee around the image area. For this feature to work the Auto Select Layer and Auto Select Groups options must be selected in the Move tool’s options bar (3).

Menu: Window > Layers
Version: 6.0, 7.0, CS, CS2, CS3, CS4

The Layers palette displays all your layers and their settings in the one place. Display the palette by selecting Window > Layers. Individual layers are displayed, one on top of the other, in a ‘layer stack’. The composite image you see in the workspace is viewed from the top down through the layers. Each layer is represented by a thumbnail on the left and a name on the right.

You can edit or enhance only one layer at a time. To select the layer that you want to change you need to click on the layer. At this point the layer will change to a different color from the rest in the stack and is now called the active layer (3).

Layers can be hidden from display in the workspace by clicking the eye symbol (4) on the far left of the layer so that it is no longer showing. This action removes the layer from view but not from the stack. You can redisplay the layer by clicking the eye space again.

The blend mode (1) and opacity (2) of individual layers can be altered using the controls at the top of the palette. New layers (5) as well as new adjustment layers (6) can be created by clicking the buttons just below the Blend and Opacity controls. The Dustbin button (7) is used to delete unwanted layers and the Lock Transparency (8) and Lock All (9) buttons are used to restrict layer changes.

Menu: Layer > New > Layer via Cut
Shortcut: Shft Ctrl/Cmd J
Version: 6.0, 7.0, CS, CS2, CS3, CS4

The Layer via Cut command cuts the contents of a selection, creates a new layer and pastes it into the layer.

If the detail is cut from a background layer then the empty space is filled with the background color. When the detail is cut from a layer the space is left transparent.