Understanding layers

When you put together images, you work with layers. Think of layers in Photoshop as stackable elements, each of which holds part of your image. Where an upper layer is transparent, the lower layer or layers show through. Where the upper layer has pixels that aren’t transparent, those pixels either block or interact with pixels on the lower layer. (You control that interaction with blending modes and opacity, explained later in this chapter.)

Take a look at Figure 10-1 (which reveals how Figure 13-3 is created). The Layers panel shows the individual layers and their content. The individual elements come together to create a single image.

You can manipulate the content of each layer independently — moving, resizing, erasing, painting, or adjusting color and tonality — to suit your needs and artistic vision. Remember to click a layer in the Layers panel to make that layer active for editing. The Move tool’s Options bar offers the option Auto-Select: Layer (and Auto-Select: Group), which enables you to make a layer (or group) active by clicking any visible pixels on that layer (or in that group).

You can link two or more layers so that they maintain their positions relative to each other as you move them. (⌘  /Ctrl+click to select the layers in the Layers panel; then click the Link button at the bottom of the Layers panel — a Link symbol appears to the right of linked layers when active in the Layers panel.) Linked layers can be moved together without knocking them out of alignment.

The left column in the Layers panel, known as the eyeball column (for an obvious reason) allows you to hide a layer, making the content of the layer invisible. The pixels are still there; they’re just not visible. Click the eyeball icon to hide the layer and then click the empty space in the left column to make the layer visible again. You can hide and show adjustment layers, too, which lets you see their impact on the image. (Read about adjustment layers in Chapter 8.)

When working with complex images containing many layers, you can use the filtering buttons and the menu at the top of the Layers panel (which shows Kind by default) to show only certain layers — perhaps only the type or adjustment layers in the image. You can also isolate layers by selecting one or more layers in the Layers panel and selecting from the filtering menu at the top-right of the Layers panel or by choosing Select ⇒ Isolate Layers. Only the isolated layer(s) are visible in the Layers panel and can be edited. To restore all the layers, deselect Isolate Layers in the Select menu, switch the filtering menu back to Kind, or right-clicking the isolated layers and select Remove from Isolation. You can also choose Select ⇒ All Layers to show the entire content of the Layers panel.

One key concept about layers is well illustrated in Figure 10-1. The higher a layer is in the stacking order (the order of layers in the panel from the top down), the more “in front” it will be. The layers Clouds-Dark and Clouds-Light are on top of everything in the image. The layer Man is in front of everything except the clouds. Because of the stacking order, the man appears to be standing on top of the musical notes, and the notes appear to be on top of the DVD.

You can also create groups, which are two or more layers packaged together in the Layers panel so that you can show or hide them together. As you can see in the Layers panel in Figure 10-1, you can have nested groups: a group within a group. The group named Background Items includes another group, named Sun, as well as several layers that aren’t part of the Sun subgroup.

Video layers can also be added to your projects, but generally speaking, you’re more likely to add regular pixel layers, type layers, shapes, and adjustment layers to a video project than to add video layers to another sort of project. Working with video is discussed in Chapter 17.

Why you should use Smart Objects

Smart Objects provide you with additional flexibility in Photoshop. When working with Smart Objects, you preserve your editing options without risk to the image quality. For example, you can transform a Smart Object as often as you like because each time you rotate or scale or otherwise manipulate a Smart Object, Photoshop goes back to the original pixels and resamples again. This prevents the sort of image degradation — especially loss of fine detail — in the image you would see if you were to shrink, enlarge, or rotate a regular layer’s content numerous times.

When working with Smart Objects, you can apply a filter to a selection in Photoshop and then later go back and change the filter settings or even remove the filter entirely. But this feature is available only when you’re working with Smart Objects. Again, it goes back to Photoshop’s ability to return to the original source pixels when working with Smart Objects. (Filters are discussed in Chapter 15.) In the Layers panel, Smart Filters very much resemble layer styles: You can click an eyeball icon to temporarily hide a filter’s effect, and you can double-click the filter name to reopen the dialog box so that you can make changes. (See Figure 10-2.)

If you want to apply a Smart Filter to only a section of a Smart Object, make a selection before selecting the filter. In keeping with the whole concept of “smart,” the filter is applied to the entire Smart Object but the filter’s visibility is controlled with a mask. (An empty filter mask is visible to the left of the words Smart Filter in the Layers panel in Figure 10-2.) And, of course, you can — at any time — paint in the mask with black, white, and shades of gray to alter where the filter is visible. (Painting in masks is discussed later in this chapter.) Note, too, that a Smart Object can have both Smart Filters and a layer style.

When you choose File ⇒ Place Embedded or Place Linked, a Smart Object is automatically created. To create a Smart Object from an existing layer (even a Background layer), choose Layer ⇒ Smart Objects ⇒ Convert to Smart Object. When you choose Place Embedded, a copy of the placed image is added to your working document. When you choose Place Linked, the file itself is not added to your document; only a line of info in the document’s metadata noting the location of the placed image.

If you link a placed document and later move it on your drive or to another drive or change its name, the link is broken and when you re-open the document into which you placed the image, it can’t be found. Also keep in mind that if you send the document to another person you’ll need to include the linked file. While embedding a placed image increases the size of the working document, it can avoid all sorts of problems that can arise from linking a placed document.

When working with Raw images, hold down the Shift key and Camera Raw’s Open Image button changes to Open Object. If you want Open Object to be the default, click the line of image info below the preview (between the Save Image and Open Image buttons) to open Workflow Options. That’s also where you specify the default color profile and bit depth of images opened through Camera Raw.

Using the basic blending modes

The pop-up menu near the upper-left corner of the Layers panel offers more than two dozen different blending modes. A layer’s blending mode determines how the pixels on that layer interact with the visible pixels on the layers below.

Because a layer named Background can’t have any layers below it, you can’t change the blending mode of background layers. Convert a background layer to a regular layer by clicking the Lock icon to the right of the layer name.

In Figure 10-3, the black-white and rainbow strips of gradients overlaid on the garden photo below each use the blending mode shown by the text outline. (You can see the original gradients in the Normal stripe.) Normal, Multiply, Screen, Overlay, and Luminosity are the blending modes you’re most likely to use regularly.

When working with layer blending modes, always keep in mind that you can use the Layers panel’s Opacity and Fill sliders to help determine the layer’s visibility and appearance. The Opacity slider controls the visibility of the layer’s content and any layer style applied to the layer. The Fill slider controls the visibility of the layer content without hiding any layer style. For a practical example of the difference between the two sliders, take a look at the section “Opacity, fill, and advanced blending” in Chapter 12.

The Layers panel blending mode pop-up menu is divided into six sections, based loosely on how the pixels on the upper layer affect the pixels on the lower layer. Here’s a quick look at how you use the key layer-blending modes:

• Normal: Photoshop picks Normal by default. Pixels on the upper layer completely hide the pixels on the lower layers (subject, of course, to the Opacity and the Fill settings). Use Normal to show the content of the layer without any interaction with lower layers.
• Multiply: The Multiply blending mode darkens where your upper layer is dark and ignores white. Use Multiply when you want the upper layer to darken but not obscure the lower layer and also for shadows and dark glow effects.
• Screen: The Screen blending mode — the opposite of Multiply — uses lighter pixels to lighten the pixels below. Use it for highlights and light-colored glows.
• Overlay: Overlay works like a combination of Multiply and Screen. Use it when you’re working with an upper layer that includes both dark and light pixels that you want to interact with pixels on layers below.
• Soft Light: Soft Light is a subtle blending mode. Like Overlay, where your upper layer’s pixels are dark, the lower layer is darkened; where they’re light, the lower layer is lightened. Soft Light is like adding a diffused spotlight to the lower layer — useful for adding a little drama to the lower layer.
• Hard Light: The Hard Light blending mode is much like a more vivid version of Soft Light. Use it to add a lot more drama to the lower layer. Hard Light works well with colors that aren’t overwhelmingly bright.
• Difference: Where the upper layer (using the Difference blending mode) and the lower layer are exactly the same, you see black. Where the two layers are different, you see brightness or color. For example, use Difference (temporarily) when trying to align two overlapping photos. Set the upper layer to Difference, move the upper layer until the areas of overlap show black, and then switch the upper layer’s blending mode back to Normal.
• Color: When the upper layer is set to Color, the lower layer’s brightness and saturation are retained, and the upper layer’s color is used. If you want to create a color picture from a grayscale picture, convert the image to RGB (choose Image ⇒ Mode ⇒ RGB), add a new layer, change the upper layer’s blending mode to Color, and paint on the upper layer (as shown in Figure 10-4).
• Luminosity: When the upper layer is set to Luminosity, the color and saturation of the lower layer are retained, and the brightness (luminosity) of the upper layer is applied. Because the luminosity (dark and light) generally provides texture, use this blending mode to produce detail in the lower layer.

Photoshop also offers two pairs of blending modes that you might find useful, but confusing. Lighten and Lighter Color compare a pixel on the upper layer to the pixel immediately below to determine the resulting color. Lighten chooses the higher (brighter) value in each of the RGB color channels and produces a new color based on those three independent lightness values. Lighter Color, on the other hand, looks at the color on the upper layer created by all three channels, compares it to the color on the lower layer, and makes visible whichever of those two colors is lighter overall. The Darken and Darker Color blending modes work similarly, but choose the darker values.

For a look at the rest of Photoshop’s dozens of blending modes, see the appendix.

Opacity, transparency, and layer masks

Blending modes help determine how pixels on an upper layer interact with pixels on a lower layer, but those upper pixels have to be visible before they can do any interacting at all. When looking at any pixel on a layer, you have to consider four factors about transparency:

• Whether the pixel has any color to start with
• The Opacity value
• The Fill value
• Whether there’s a layer mask

When you add a layer and paint on it, for example, you color some of the pixels yet leave other pixels transparent. (Every layer in every image is completely filled with pixels, whether visible or not.) If nothing is done to color some pixels, they remain transparent, and the lower layers can be seen through that part of your upper layer. In Figure 10-5, the words upper layer are on a separate layer above the layer containing the words LOWER LAYER. Where the upper layer has transparent pixels, the lower layer shows through.

A layer named Background in the Layers panel can’t have transparent pixels. Simply click the Lock icon to the right of the layer name to convert it to a regular layer.

Lowering the Opacity or the Fill slider in the Layers panel (or the Layer Style dialog box) makes all visible pixels on the layer partially transparent: The pixels on layers below can be seen through the upper layer’s pixels. (The Opacity slider controls the pixels on the layer and any layer style; the Fill slider works only on the pixels, not the layer style.)

For a “glass text” effect, useful for adding your copyright info over an image you don’t want others to use, add the type, add a narrow stroke layer effect and perhaps a drop shadow, and then reduce the Fill slider to zero. Flip ahead to Chapter 12 for an example (specifically, Figure 12-20).

Chapter 8 discusses layer masks and vector masks. Remember that any pixel inside the mask is at least partially visible, and any pixel outside the mask is transparent, regardless of whether it has color. But, as you can guess, any completely transparent pixels inside the mask remain completely transparent.

Creating clipping groups

This being Photoshop, here is yet another way to restrict the visibility of pixels on an upper layer: clipping groups. Clipping an upper layer to the layer below, in effect, creates a mask for the upper layer. The opacity of the pixels on the lower layer is applied to the pixels on your upper layer. Where the lower layer is transparent, the upper layer (regardless of original content) becomes transparent. In the Layers panel, Option+click (Mac)/Alt+click (Windows) the line between two layers to clip the upper layer to the lower. When you hold down the Option/Alt key, the cursor turns into the icon shown between the two layers in Figure 10-6.

After you Option+click/Alt+click the line between Layer 1 and the type layer, the upper layer is visible only within the text on the lower layer. The upper layer is indented to the right in the Layers panel, with a downward-pointing arrow to let you know that it’s clipped to the layer below. Note that the upper layer’s thumbnail in the Layers panel shows the entire layer, not just the visible area. To unclip a layer, Option+click/Alt+click again on the line between the two layers in the Layers panel. Also note in Figure 10-6 that the layer style is applied to the lower layer rather than the upper layer.

Photoshop lets you show the layer thumbnails in two ways. Normally, the entire layer, including all areas of transparency, shows in the thumbnail. Although that gives you a good indication of how large or small the particular layer’s content is in the image, layers with little content have little to show in the thumbnail. By using the Panel Options (from the Layers panel menu) or Control+clicking/right-clicking the empty area below the layers in the panel, you can elect to show a thumbnail that includes only nontransparent areas of the layer. Little things fill the thumbnail, but they also appear out of proportion to the other thumbnails. Your choice.

Making composited elements look natural

One of the keys to compositing two images is a slight fade to the edges of the element you’re adding to the original image. That fade, called feathering, makes the edges of the image appear to fall off into the distance very slightly rather than having a sharply defined edge that sticks out like a sore thumb. (See Chapter 8 for full information on feathering.) You have a number of ways to feather a selection, including the following:

• Use the Feathering field on the Options bar before you use a selection tool.
• Use the Select and Mask button on the Options bar or the Select ⇒ Select and Mask command after making your selection.
• Choose Select ⇒ Modify ⇒ Feather after you make a selection.
• Use one of Photoshop’s Blur filters on a saved selection’s alpha channel in the Layers panel (or on a layer mask).

Matching color between two layers is also critical for a natural appearance. Take a look at Chapter 6 for full information on Match Color and Photoshop’s other color adjustment capabilities.

You also need to be aware of perspective and scale. When an element in your composited image seems to be too large or too small or when it seems to be facing the wrong way or standing on air, rely on the Edit ⇒ Transform commands. Although the Scale and Rotate commands are self-explanatory, Figure 10-7 shows visually how you can use the other Transform commands, such as Skew, Perspective, and Warp. Drag the bounding box anchor points to transform the selected pixels.

The Edit ⇒ Transform ⇒ Warp command adds a simple mesh over the content of the layer or selection. You click and drag the direction lines for the corners of the mesh and at the intersection of mesh lines to distort your artwork. As you see in Figure 10-8, the Warp distortion gives you a level of control second only to Photoshop’s Liquify feature (discussed in Chapter 15). You can also use Warp with paths and vector shapes.