This section is more or less theory or otherwise also known as a blurb, so if you feel you don't want to read this part, you are quite welcome to move on. Having said that, if you intend to do some complex image editing, or simply want to know, what the image editors mean when they talk mysteriously about "layers", then this is your chance to find out. When you have finished with this section you will have gleaned some inside information which could just pull you out of trouble later. Here goes.

Layers are Photoshop's most overrated and most underused feature. Anything you can accomplish with layers, you can accomplish without layers. Having said that, layers add flexibility. Each layer in a composition is independent of other layers, which allows you to change your mind at a moment's notice. Layers are also uniquely versatile, meaning that editing pictures in layers becomes a bit easier, once you get comfortable with the concept. Layers make it harder to make mistakes, they make it easier to make changes, and they expand your range of options.

Layers are created for you by Photoshop most of the time without as much as a by your leave, at least most of the time. The type tool creates a new layer, dragging and dropping a selection with the move tool makes a new layer, and the Paste command adds a new layer. Even Edit; Paste Into results in a new layer.

To create an empty layer, useful when you want to create a few brushstrokes without harming the original image choose Layer, New, and Layer. Or simply click the new layer icon at the bottom of the Layers palette.

Copy a selection and paste it into another image. Photoshop pastes the selection as a new layer.

If you want to add a selected portion of one image to another image, the easiest method is to Ctrl+Drag the selection and drop it into its new home. Be sure to Ctrl+Drag or use the move tool. If you merely drag the selection with the marquee, lasso, or wand, you drop an empty selection outline into the new Image window.

To name a layer double click its name in the Layers palette. Enter a new name and press Enter.

You can duplicate the layer into an entirely different image by Alt+dragging the layer onto the new layer icon in the Layers palette.

Photoshop lists the layer along with a little thumbnail of its contents in the Layers palette. The little paintbrush icon in front of the layer name also indicates an active layer.

To the left of the paintbrush icon is a column of eyeballs, which invite you to hide and display layers temporarily. Click an eyeball to hide the layer. Click where the eyeball previously was to bring it back and redisplay the layer.

You can select a different layer by clicking its name in the Layers palette. This layer becomes active, enabling you to edit it. Unfortunately, only one layer may be active at a time in Photoshop.

Although the selection outline is lost when you convert a selection to a layer, no information is lost. Anything that wasn't selected is now transparent. The data that defines the opacity and transparency of a layer is called the transparency mask.

To see this transparency in action, click the eyeball icon in front of the background item in the layers palette (this is assuming you have an image open with at least two layers created). This enables you to view the new layer by itself. The transparent areas are usually covered in a checkerboard pattern.

At the bottom of the layer stack is the background layer, the fully opaque layer that represents the base image. The background image is as low as you go. Nothing can be slipped under the background layer and pixels in the background layer cannot be made transparent, unless you first convert the background to a "normal" layer.

To make the conversion, double-click the background item Layers palette. Then enter a new name for the new layer, and press Enter.

To add a new background layer, Alt+click the new layer icon at the bottom of the Layers palette. When the New Layer dialog box appears, select the Background option from the Mode pop-up menu, then press Enter.

Two ways exist to reorder layers in Photoshop. First, you can drag a layer name up or down in the scrolling list to move it forw3ard or backward in layering order. The only trick is to make sure the black bar appears at the point where you want to move the layer before you release the mouse button. The second way to reorder layers, by choosing a command from the Layer, Arrange submenu. You can also move layers using some short cut keys from the Keyboard, if you are so inclined.

Ctrl+Shift+]: to move the active layer to the top of the stack.

Ctrl+Shift+[: this shortcut moves the active layer to the bottom of the stack, just above the background layer.

Ctrl+]: this moves the layer up one level.

Ctrl+[: this moves the layer down.

Layers are wonderful to work with, but with all things wonderful, they too have their price. Layers expand the size of an image in RAM and can cause your PC to perform slower than usual. The other downside is that you can only save layered images in one format, the native Photoshop format (.PSD).

Photoshop provides some ways of merging layers together.

Merge Down: Choose Layer, Merge Down to merge a layer with the layer immediately below it.

Merge Visible: Choose the Merge Visible command to merge all visible layers into a single layer. If the layer is not visible, that is, if no eyeball icon appears in front of the layer name, Photoshop doesn't eliminate it, the layer remains independent.

Flatten Image: This command merges all visible layers and throws away the invisible ones. The result is a single, opaque background layer. Once flattened, the layers, which existed before, can not be invoked separately again.

You can also merely throw a layer away, drag the layer name onto the trash can icon at the bottom of the Layers palette. Or click the trash can icon to delete the active layer.

As said earlier, only one file format, the native Photoshop format, saves images with layers. If you want to save a flattened version of your image, that is, with all layers fused together into a single image, into another file format. Then choose File, Save a Copy and select the desired format from the Save As pop-up menu.

Transformations are useful to know as they can affect a selection, a layer, multiple layers, or an entire image at a time. These transformations include scaling, rotating, flipping, slanting and distorting. Those transformations that affect the entire image are listed in the Image menu, those that affect layers and selections are found in the Layer menu.

Scale: to resize the image, use Image, and Image size. This command is useful, as scanned images are sometimes blown out of proportion, this command is one way to bring them to heel.

Rotate: to rotate the entire image, choose a command from the Image, Rotate Canvas submenu. To rotate an image scanned on its side, choose the 90 CW (clockwise) or 90 CCW (counter clockwise) command. Choose 180 to spin the image on its head.

Flip: choose Image, Rotate Canvas, Flip Horizontal to flip the image so left is right and right is left. To flip the image upside down, choose Image Rotate Canvas, Flip Vertical.

Free Transform: this is one of the best transformation tools. It enables you to scale, flip, rotate, slant, distort, and move a selection or layer in one continuous operation. This one command enables you to get all your transformations exactly right before pressing Enter to apply the final changes.

To initiate the command, press Ctrl+T or choose Layer, Free Transform. Photoshop surrounds the layer or selection with an eight-handle marquee. You are now in the free transform mode, which prevents you from doing anything except transform, the image until you apply the operation or cancel it.