Do you use layers when editing your digital photos? If not, you're missing out on the single most powerful tool in your photo editing repertoire. Layers may seem baffling at first, but they're not hard to use — and they unleash all sorts of powerful digital editing tricks. You can use layers to make double exposures, achieve special effects like "selective colour" partial black and whites, and even just get better exposure correction.
Layers are really just what they sound like. Imagine taking two photos and laying one on top of the other. You can't see the one on the bottom, of course. Now imagine that you have the ability to make the top photo somewhat transparent, so the other photo shows through from below. That's the concept of layers in a nutshell. In most photo editing programs, you can add as many layers as you like, and vary the "opacity" of each layer — the lower the opacity, the easier it is to see the underlying layers.
A layer can be made of almost anything. You can layer two different photos, or copies of the same photo. A layer can even be a graphic element, such as a solid color. You usually control your layers using a Layer Palette, such as the one that can be found in Adobe Photoshop Elements.
Adding a Layer
So how do we get started? There are a lot of ways to add two photos to a project using layers, but let's begin with one easy way. I'll describe the process using Adobe Photoshop Elements, but the technique translates pretty well to many other photo editors.
To begin, open two photos in Photoshop Elements. You'll see them in the Project Bin at the bottom of the screen, but only one will be in the workspace at a time.
Let's copy the image in the workspace: press Ctrl-A to select the entire photo, then press Ctrl-C to copy it to the clipboard.
Next, double-click the other photo in the Project Bin. That image should now be in the workspace. In the menu, select Layer, New, Layer and click OK in the New Layer dialogue box. You should now see an empty, transparent layer on top of the photo in the Layer Palette.
Press Ctrl-V to paste the copied image into the layer. The workspace will be replaced with the new image, but fear not: the other photo is still there, underneath. You can't see it though, because the top layer is totally opaque.
To prove that I'm telling you the truth, look in the Layer Palette. You should see two images in different layers. You can "turn off" the top layer by clicking the Eye icon to the left of the top layer. To turn the layer back on again, toggle the Eye.
Want to vary the transparency of the top layer so the bottom photo shows through? Make sure the top layer is selected& #8212; click it in the Layer Palette — and then adjust the Opacity control.
You can also change the position of the layers. If you decide that you want the bottom layer on top, just drag it there. There's just one catch: the original bottom layer is locked as the background layer by default (that's what the padlock icon means). To move it, you need to promote the layer first. To do that, double-click the bottom layer and then click OK in the New Layer dialogue box. Now you can drag the bottom layer above the top layer to switch their position.
Using Color Selectively
Now that you understand the basics of Layer manipulation, let's make a photo with selective color — in other words, most of the photo will be black and white, with a splash of color in it.
Start by opening a photo in Photoshop Elements. Then select the photo (Ctrl-A) and copy it (Ctrl-C). In the menu, choose File, New, Image from Clipboard. The Project Bin should now show two identical images; we'll turn one black and white. Choose Image, Mode, Grayscale. Select this image and copy it.
Double-click the color version of the image in the Project Bin to switch to it, and then choose Layer, New, Layer. Click OK. Press Ctrl-V to paste the black and white version of the image into the top layer.
Now it's time for the fun. Click the Eraser Tool in the toolbar on the right side of the screen (it's 16th from the top) and start erasing. You might need to adjust the size of the Erase Tool using the Tool Options toolbar at the top of the screen. Everywhere you paint with the Eraser, you'll see color bleed through from the bottom. This is an easy way to add color selectively to a monochrome photo.