The best way to think of a layer is to look at it like a sheet of clear plastic. If you lay this plastic on top of an image, you can paint on it, place text on it, or put another image on it, without affecting the image underneath. Moreover, you can put additional sheets of clear plastic (layers) that contain graphics or parts of an image on top of other sheets to compose a complete image out of many components. You can even apply styles and transparency effects to each individual layer if you wish.

 

If a layer contains no image information it will be totally clear. That is to say, it will be completely transparent and the underlying layers or image will be visible. If the top layer contains an image, and the opacity for the layer is set at 100%, the layer will be opaque. (I.e. you will not see the underlying image or layers.) If a layer contains only part of an image, the part of the layer with no image data will be transparent.

 

The crucial feature for layers is the ability to perform a number of actions on a layer by layer basis. As mentioned above, you can adjust the opacity of each layer individually. You can also set each individual layer to be visible or invisible. Perhaps more importantly, there are a number of stylistic effects, image edits, and retouches that you can perform on individual layers.

 

You can create a layer over your image to allow you to perform edits without affecting the original.

 

You can compare multiple effects or retouches by using a different layer for each one, and then toggling them on and off against the background image.

 

You can create a layer over your image and then add a part of an image, or a complete image to the new layer. You can then move the new image around, adjust the transparency, and apply effects to blend the two images in any number of ways.

 

 

 

This image is composed of two layers. One layer contains the Dune image and the other contains a selection from the Eagle image.

 

The selection has been modified with the blur and smudge retouch tools, and the opacity of the selection layer has been reduced to 63%

 

The following picture shows the layer palette for the composite eagle/dune image.

 

 

If you look closely at the small preview for Layer 1 in the Layers Palette, you will see a checker pattern behind the eagle. Wherever you can see this pattern, the layer contains no image data. This means that any part of a layer with this checker pattern will be transparent.

 

When you add layers to an image, and you want to keep the layer information separate and intact, save the file in PSD format. This Photoshop Document format will preserve all of the individual layers and related information so you can retrieve the document at a later date and continue to work with the original layers. If you save your layered image as another format type, like GIF or JPEG, the layers will not be preserved as separate editable components. The layers will be amalgamated to form one image and will not be retrievable as separate entities later.