Do you edit your digital photos using layers? 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 permit all sorts of powerful digital editing tricks.
You can use layers to combine photos, create double exposures, achieve special effects like selective color in a partly black-and-white image, and even correct a shot's exposure or color balance.
What Layers Do
Imagine taking two photos and laying one on top of the other. You can't see the one on the bottom, of course. But suppose that you could make the top photo somewhat transparent, so that the other photo showed through. That, in a nutshell, is the concept of layers.
In most photo editing programs, you can add as many layers as you like, and you can vary the opacity of each layer: The lower the opacity, the more readily visible the underlying layers will be. A layer can be composed of almost anything. You can layer two different photos, or two copies of the same photo. A layer may even be a solid color. You usually control your layers by working with a Layer Palette, such as this one in Adobe Photoshop Elements.
Add a Layer
There are lots of ways to use layers to add two photos to a project, but let's begin with a simple method. I'll describe how the process works in Photoshop Elements, but the technique translates to many other photo editors as well.
To add a new layer to any image in Photoshop Elements, select Layer -> New -> Layer from the top of your screen (or press Shift-Command-N) and click OK in the New Layer dialog box. To combine images, start by opening 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. Your first task is to copy the image in the workspace: Press Command-A to select the entire photo, and then press Command-C to copy it. Next, double-click the other photo in the Project Bin to make that image appear in the workspace. Press Command-V to paste the copied image. It will automatically appear on its own new layer, and that layer will appear on top of the original photo in the Layer Palette. Your workspace will show the new image, but fear not: The other photo is still there, underneath.
Do Basic Editing with Layers
In the Layer Palette, you should see two images in different layers. You can toggle the top layer off and on by clicking the eye icon to the left of the top layer. To vary the transparency of the top layer so that the bottom photo shows through, select the top layer (by clicking 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: By default, the original bottom layer is locked as the background layer (that's what the padlock icon means). Before you can move it, you must promote the layer. To do that, double-click the bottom layer and then click OK in the New Layer dialog box. Now you can drag the bottom layer above the top layer to switch their position.
Use Color Selectively
Now let's try making a photo with selective color: Most of the photo will be black-and-white, but it will also contain a splash of color. Open a photo in Photoshop Elements, select the photo with Command-A, and copy it using Command-C. Choose File -> New -> Image From Clipboard. At this point, the Project Bin should show two identical color images; we'll convert one of them to black-and-white. Choose Image -> Mode -> Grayscale. Select the image and copy it.
Double-click the color version of the image in the Project Bin to switch to it, then press Command-V to paste the black and white version of the image into a new top layer. Now let's add some color. Click the Eraser tool in the toolbar on the left side of the screen and start erasing. Use the Tool Options toolbar at the top of the screen to adjust the size of the eraser. Everywhere you paint with the Eraser, you'll see color bleed through from the bottom layer. For more control, choose the Smart Selection tool and select the area of your image that you'd like to appear in color. When you use the eraser, it will only erase within that selection.
You can also improve your photos by using adjustment layers. Open the photo that you want to edit in Photoshop Elements. In the menu, go to Layer -> New Adjustment Layer to see a list of adjustment layer options.
To adjust your photo's exposure, you can use Levels (which lets you make histogram adjustments) or Brightness/Contrast. If you want to change the color saturation, or even bleach your photo so that it becomes a nearly monochromatic image, try Hue/Saturation.
In this instance, choose Levels and click OK on the New Layer dialog box. You will see the Levels histogram, which you can manipulate to improve the exposure of you photo.
Adjust the white point, black point, and gamma to your taste. For more infomation on how to use a histogram, read this article on tone and this article on color correction. When you're satisfied with the results, click OK. If this were a single-layer photo, you'd be done at this point; anything that you did to the levels would be baked into the original image. But that's where the magic of layers becomes evident: Our various manipulations so far haven't affected the original photo at all. As a result, you can now blend the original photo with the adjustment layer by using the Opacity control. Click Opacity in the Levels Palette and back off from 100 percent; when you reach a combination of the two levels that you like, stop.
Tricks for Manual Adjustment Layers
What if your photo editing program has some basic support for layers, but no "adjustment" layers? Or what if there's no option for the kind of adjustment you'd like to make? No problem; doing it manually is easy. Suppose that you want to sharpen a photo, for example. There's no Adjustment Layer menu option for sharpening in Photoshop Elements.
Here's one way to perform this task: Open a photo and create a duplicate layer. Now, with the top layer selected in the layer palette, select Enhance -> Unsharp Mask and set the sharpness as desired. You might even want to oversharpen the photo a little, because afterward you can use the opacity slider to back it down until it's just right. Once you've made an adjustment like this in a layer, you can use selectively remove the effect from the image by using the Eraser tool. You might want to erase sharpening from people's faces, for example, while leaving their clothes and the background sharpened.
Punch Out the Subject With Magic Extractor
Another common way to use layers is to "punch out" (that is, remove) the subject from one photo and insert it into another. The subject and the background, of course, will exist as separate layers. First, we'll use Photoshop Elements' Magic Extractor to do this the easy way. This feature lets you select the subject (the foreground) and the background; then it automatically punches out the subject for you.
Open a photo, and choose Image, Magic Extractor, or select the Magic Extractor. The Foreground Brush tool is automatically selected; you'll use this to identify your subject. It's important to mark regions that change color so the Magic Extractor will recognize that they're still part of the main subject. When you're done highlighting the subject, click the icon for the Background Brush tool and paint sections around the subject to indicate the parts of the photo you don't need. If you make a mistake, use the Point Eraser tool to undo any unwanted marks. When you think you've adequately marked your photo, click Preview. You can continue painting with the foreground and background tools if necessary, and make corrections with the eraser. When you're done, click OK, and the subject will appear on its own. From here, you can copy it into another photo or add a custom background to it.
Pluck Out the Subject With Basic Selection Tools
If you have an older version of Photoshop Elements (one that lacks the Magic Extractor) or another program altogether, you'll need to isolate the subject by hand. As long as your image editor has some sort of selection tool, though, you can get similar results.
In older versions of Photoshop Elements, activate the Magnetic Lasso tool, and then choose a small feather value (the higher the photo's resolution, the more feathering you'll want). Next, click on an edge of your subject and slowly move the tool along the edge. The "magnetic" property of the tool will snap the selection to the edge as you go. At certain points, you may need to click to lock in a key point, especially around sharp curves or areas of low contrast. If you make a mistake, press the Delete key. When you get all the way around, double-click to close the selection. Choose Edit -> Copy, and then choose Layer -> New -> Layer Via Copy. You'll have a new, blank layer containing your selected subject.
Drop the Subject Onto a New Background
After you've isolated your subject from the background—by using a feature like Magic Extractor or some other selection method—it's time to add it as a new layer to a different photo.
To begin, open the photo that you want to transfer the subject to. If you're using Photoshop Elements, you should see both images in the Project Bin at the bottom of the screen. Switch to the first photo—the one with the extracted subject—and click the Hand tool, (the third icon from the top of the toolbar). Press Command-A and Command-C to select the whole image and to copy it to the clipboard. Then switch to the other photo and press Command-V. The subject should appear as a new layer in the photo. Because the two photos might be different in size or scale, you may need to grab the copied photo by a corner handle and resize it until it looks right. Afterward, you can tweak the photo using other layer effects until the image is perfect.
This story, "Basic photo editing tricks with layers" was originally published by PCWorld.