Working in Layers | Real World Print Production

While the intricacies of creating and editing Photoshop layers are beyond the scope of this chapter, it's worth mentioning some of the benefits of working with layered files. Layers can keep the individual components of a complicated composition from being glued together prematurely, giving you a safety net in case you change your mind. Multiple undo capabilities are great during a working session, but they don't help if you've saved a file and realizedays laterthat you've inadvertently cropped out something crucial, or performed a color correction that doesn't look so great.

Layers offer the advantage of providing nondestructive methods for combining images, for creating silhouette and soft-edged effects, and for doing color corrections without permanently altering pixels.

Don't Erase that Pixel!

When you need to eliminate part of an image, it's tempting to just choose the Eraser tool from the Tools palette in Photoshop, and get rid of it. When you permanently delete pixels, they're gone forever (Figure 9.2). If you accidentally erased the CEO's left ear in his portrait for the prestigious annual report, I hope you remember where you backed up the original image. I'll wait while you frantically search through that pile of CDs.

Figure 9.2. Nice seashore! Well, it was. Too bad you accidentally erased the ocean and some of the scenic rocks (right). But you still have the original image somewhere. Don't you?

There's a safer and more flexible way to eliminate pixels. Use the Layer Mask feature in Photoshop to selectively hide pixels without destroying them. If you can create a silhouette, you can create a layer mask.

Create a selection by using your favorite method, and make sure it's still an active selection. An active selection appears as a black-and-white dashed shape, often referred to by the highly technical term "marching ants."
The layer must be a floating layer to use a layer mask. If the layer is named Background (and its name is italicized), it needs to first be converted to a floating layer. To do this, double-click the layer name. In the dialog box that follows, you can enter a new name for the layer or accept Photoshop's default name for the newly floating layer.
Make sure your ants are still marching, and then select Layer > Layer Mask > Reveal Selection. You should see the selected part of the image floating on a transparent background, and a mask icon will be added to the layer in the Layers palette (Figure 9.3).

Figure 9.3. A layer mask reveals content rather than erasing pixels. You can always modify the layer mask later, to reveal or hide image contents in a nondestructive way.

Color Corrections with a Safety Net

Some of the color-correction options in Photoshop, including Shadow/Highlight, Match Color, and Replace Color, can only be applied directly to pixels in the image, which alters them permanently. But some of the most commonly used color corrections can be stored in Adjustment layers, which are nondestructive. No pixels are harmed in this type of color correction, and you can always change your mind later. To use an Adjustment layer, click the circular "Create new fill or adjustment layer" icon ( ) at the bottom of the Layers palette, and then select the desired type of correction you wish to make. You can also choose Layer > New Adjustment Layer, and then select a color-correction option from the menu that is displayed. You can choose from a wide assortment of color-correction options, including Curves, Levels, Color Balance, and Brightness/Contrast. When you complete your corrections and click OK in the dialog box, you'll see a new entry in the Layers palette (Figure 9.4).

Figure 9.4. An Adjustment layer performs a color correction without actually altering pixels. Don't like it? Delete it or click the eyeball to hide the correction.

Note that the Adjustment layer automatically creates a layer mask for itself. Initially, it's all open (that is, it isn't hiding anything). But if you'd like to prevent the color correction from affecting some areas of the underlying image, use the Paintbrush tool to paint those areas of the mask with black. If you want to rework the color correction, double-click the leftmost icon in the Adjustment layer to display a dialog box. To disable the correction, click the eyeball to turn off the visibility of the Adjustment layer. To permanently delete the Adjustment layer, select the layer in the Layers palette, and then choose Delete Layer from the Layers palette menu.

Should You Flatten a Layered File?

Native Photoshop files offer the benefits of layers and transparencywhat's not to love? Admittedly, if a Photoshop file has grown to hundreds of megabytes, it might be more efficient to use a flattened file for placement into a page layout. But you'd be wise to keep a copy of the original, layered, working Photoshop file in case you need to do additional edits. To flatten a layered file, choose Flatten Image from the Layers palette menu.