Understanding Layers in Your Image Editor

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What are Layers?

Layers Example
The large square shows three layers stacked--a fish, a butterfly, and a star. The three smaller squares show the contents of each layer. The checkerboard pattern represents the transparent areas and is not part of the layer. © Sue Chastain
If you've never explored layers in your graphics software, you are really limiting yourself. Working on a single background layer can be very unforgiving as any work that you do permanently alters the pixels. Sure, you can undo, but when you start working with layers you will have much more flexibility with what you can do. This article provides a basic for understanding layers in many image editing programs.

Understanding Layers

If you're totally unfamiliar with layers in graphics software, they can be a bit difficult to grasp at first. You can think of each layer in a document as a sheet of clear transparent film. When you paint on one of the sheets, you can still see through the unpainted areas of the sheet. When you stack the sheets, the painted areas on the lower sheets will show through the transparent areas of the sheets above.

In Photoshop and most other image editing software, the transparent portions of a layer are displayed as a gray and white checkerboard pattern (unless the image contains a background). The checkerboard pattern is not part of the document, it's just there to help you identify the transparent areas.

Take a look at the example shown here. The large square shows three layers stacked--a fish, a butterfly, and a star. The three smaller squares show the contents of each layer. You can tell by the way the objects overlap that the fish is at the bottom of the stack, the butterfly is in the middle, and the star is at the top of the stack. Your image editing software treats each layer as if it were a separate document so that any editing functions are only applied to the active layer.

When you open an image such as a digital photo in your image editor, normally the image opens with only a background layer. The background is a special layer that cannot have transparency and always remains on the bottom of the stack. When you stack additional layers above the background, the background will show through the unfilled portions of the layers above it.

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The Layers Panel

The Layers Panels for Photoshop CS5 and Photoshop Elements 9
The layers panel for Photoshop CS5 (left) and Photoshop Elements 9 (right). © Sue Chastain
In Photoshop, you use the layers panel for managing the layers in a document. Other graphics software will have a similar layers palette or panel. Shown here is the layers panel for Photoshop CS5 (left) and Photoshop Elements 9 (right) using the same example file that was used on the previous page. (I've enlarged the thumbnails for this screen shot so you could better see the layer contents.)

The layers panel shows you the stacking order of the various layers in your document along with a thumbnail to help you identify each layer at a glance. You can only edit the contents of one layer at a time, although you can select multiple layers for performing transformations and such. The active layer will be highlighted in your layers panel.

We'll explore the Photoshop layers panel in more detail in a future lesson.

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Layers in Paint.NET

Paint.NET is a free pixel-based image editor that offers support for layers. You can learn more about the layers palette in Paint.NET from the following article.
• Anatomy of the Layers Palette in Paint.NET