Layer Basics

Regardless of how you create a new layer, Photoshop lists the layer along with a little thumbnail of its contents in the Layers palette. The new layer appears highlighted to show that it's active, and the layer's name appears in bold.

To the left of the layer thumbnail is the visibility column, containing boxes, each with an Eye icon in it. This column allows you to hide (the eye disappears) and display layers temporarily. Click an Eye icon to hide the layer. Click where the Eye icon previously was to bring it back and redisplay the layer. Whether hidden or displayed, all layers remain intact and ready for action.

Tip  

To view a single layer by itself, Alt+click (or Option+click) the Eye icon before the layer name to hide all other layers. Alt+click (Option+click) in front of the layer again to bring all the layers back into view.

Switching between layers

You can select a different layer by clicking its name in the Layers palette. The layer you clicked becomes active, enabling you to edit it. New to Photoshop CS2, you can also click and activate multiple layers ” just click the first layer you want to select, and then hold down the Shift key to select additional consecutive layers ( next to each other in the Layers palette, not necessarily in the image) or the Ctrl key ( z key on the Mac) to select nonconsecutive layers. After the multiple layers are selected, you have limited abilities to do things to them: you can move them with the Move tool, and you can transform them as a unit. This is not the same as grouping them, which is discussed later in this chapter.

You can also link multiple layers and combine them into groups ” that's also explained later. You then have the same ability to move and transform the linked layers (press Ctrl+T or z +T to enter Free Transform mode) as you do when you simply Shift+click or Ctrl+click ( z +click for Mac) the layers to select them. You cannot, however, paint, draw, fill, or apply filters to the selected or linked layers. If you want, you can formally merge the layers into a single layer, which you can then treat like any other layer. More about that later, too.

Tip  

If your image contains several layers ” like the one back in Figure 5-1 ” it might prove inconvenient, or even confusing, to switch from one layer to another in the Layers palette. Luckily, Photoshop offers a better way. With any tool, Ctrl+Alt+right- click ( z +Option+Control+click on the Mac) an element in your composition to go directly to the layer containing the element. For example, Ctrl+Alt+right-clicking on the woman 's face in Figure 5-1 takes you to that specific layer.

Why such an elaborate keyboard trick? Here's how it breaks down:

  • Ctrl ( z on the Mac) gets you the Move tool. If the Move tool is already selected, simply Ctrl+ or z +clicking works just fine. This is new in CS2. In previous versions you'd Alt+right-click, or Option+Control+click (Mac).

  • Right-clicking (Control+clicking on the Mac) brings up a shortcut menu. When you right-click or Control+click with the Move tool ” or Ctrl+right-click or z +Control+click with any other tool ” Photoshop displays a pop-up menu that lists the layer that the image is on and any other layers in the image, as shown in Figure 5-6. (If a layer is completely transparent at the spot where you right-click or Control+click, then that layer name doesn't appear in the pop-up menu.) Select the desired layer to go there.

    image from book
    Figure 5-6: The image window's contextual menu lists all of the layers in the image that contain pixel data at the spot where you clicked.

  • The Alt key (Option on the Mac) bypasses the pop-up menu and goes straight to the clicked layer.

Add them all together, and you get Ctrl+Alt+right-click or z +Option+Control+click, depending on your platform. It's a lot to remember, but it's a great trick once you get the hang of it.

Tip  

If you prefer to always go directly to the layer on which you click and avoid all these messy keyboard tricks, press V to select the Move tool. Click the Auto Select Layer in the Options bar. Now whenever you click a layer with the Move tool ” or Ctrl+click ( z +click on the Mac) with some other tool ” Photoshop goes right to that layer. You may want to turn off the Auto Select Groups option, so that when you select a layer simply by clicking on it, you don't necessarily select the entire group of which that layer may be a member. More about groups later on in this chapter.

Photoshop CS2  

Notice the Select Similar Layers command on that menu in Figure 5-6. Similar? What does that mean? It means layers that have similar content in terms of size , shape, color , modes, and styles. It can be a great way to select several duplicate layers at once, without having to scroll through a long list of layers in the palette to find the ones you want to select for moving, resizing, linking, or dragging to another image in the workspace.

Understanding transparency

Although the selection outline disappears when you convert a selection to a layer, no information is lost. Photoshop retains every little nuance of the original selection outline ” whether it's a jagged border, a little bit of anti-aliasing, or a feathered edge. 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 Eye icon in front of the Background item in the Layers palette. This hides the background layer and enables you to view the new layer by itself. In Figure 5-7, the background was hidden to view the skeleton and moon on their own. The transparent areas are filled with a checkerboard pattern. Opaque areas look like the standard image, and translucent areas ” where they exist ” appear as a mix of image and checkerboard.

image from book
Figure 5-7: When you hide the background layer, you see a checkerboard pattern that represents the transparent portions of the layer.
Tip  

If the checkerboard pattern is hard to distinguish from the image, you can change the pattern's appearance. Press Ctrl+K and then Ctrl+4 ( z +K and then z +4 on the Mac) to go to the Transparency & Gamut panel of the Preferences dialog box. Then edit the colors as you see fit.

If you apply an effect to the layer while no portion of the layer is selected, Photoshop changes the opaque and translucent portions of the image but leaves the transparent region intact. For example, if you press Ctrl+I ( z +I on the Mac) or choose Image Adjustments Invert, Photoshop inverts the image but doesn't change a single pixel in the checkerboard area. If you click in the left column in front of the Background item to bring back the Eye icon, you may notice a slight halo around the inverted image, but the edge pixels blend with the background image as well as they ever did. In fact, it's exactly as if you applied the effect to a selection, as demonstrated in Figure 5-8. The only difference is that this selection is independent of its background. You can do anything you want to it without running the risk of harming the underlying background.

image from book
Figure 5-8: Applying the Invert command to the skeleton ayer inverts only the skeleton without affecting any of the transparent pixels. The moon and the background landscape are unaffected.

Only a few operations affect the transparent areas of a layer, and most of these are limited to tools. You can paint on transparent pixels to make them opaque. You can clone with the clone stamp or smear pixels with the edit tools. To send pixels back to transparency, paint with the eraser. All these operations change both the contents of the layer and the composition of the transparency mask.

Tip  

You can also fill all pixels by pressing Alt+Backspace (Option+Delete on the Mac) for the foreground color and Ctrl+Backspace ( z +Delete on the Mac) for the background color. To fill the pixels in a layer without altering the transparency mask, toss in the Shift key. Shift+Alt+Backspace (Shift+Option+Delete) fills the opaque pixels with the foreground color; Ctrl+Shift+Backspace ( z +Shift+Delete) fills them with the background color. In both cases, the transparent pixels remain every bit as transparent as they ever were.

When a portion of a layer (other than the background layer) is selected, pressing plain old Backspace (Delete on the Mac) eliminates the selected pixels and makes them transparent, revealing the layers below.

Note  

Transparent pixels take up next to no space in memory, but opaque and translucent pixels do. Thus, a layer containing 25 percent as many pixels as the background layer takes up roughly 25 percent as much space. Mind you, you shouldn't let this influence how you work in Photoshop, but it is something to keep in mind.

Modifying the background layer

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 floating layer.

To make the conversion, double-click the item labeled "Background" in the Layers palette. A dialog box appears. Enter a name for the new layer ” Photoshop suggests Layer 0 ” and press Enter or Return. You can now change the order of the layer or erase down to transparency.

Tip  

To skip the dialog box and accept Layer 0 as the new layer name, press Alt (or Option on the Mac) and double-click the Background item in the Layers palette.

Tip  

If you want to skip having a background layer entirely, create your new image with Transparent selected from the Background Contents option. When this option is set, the image opens with Layer 1, rather than "Background," and there are no locks or other limitations on this starting layer.

In Figure 5-9, the background landscape was converted to a layer. This particular image included a predrawn path that encircled the mountains . After Ctrl+clicking ( z +clicking on the Mac) on the path to convert it to a selection outline, Ctrl+Shift+I ( z +Shift+I) was pressed to reverse the selection. Finally, Backspace (Delete) was pressed to erase the pixels comprising the sky, as the figure demonstrates . From this point on, all of the layers can be reordered, or layers can be added behind the mountains. A new background layer can also be introduced.

image from book
Figure 5-9: After converting the background landscape to a layer, the path was selected, the selection inversed, and the transparent void below was revealed.
Note  

Although InDesign 2.0 can easily handle layered Photoshop files complete with all transparency intact, QuarkXPress 6.0 can't. If you want to export transparency to Quark, you have to use a clipping path.

Cross-Reference  

Read all about clipping paths in Chapter 7.

Tip  

To convert the active layer to a background layer when there is currently no background layer, choose Layer New Background From Layer. It doesn't matter whether the active layer is at the top of the stack, the bottom, or someplace in between ” Photoshop takes the layer and makes a new background out of it. To establish a blank background, create an empty layer by pressing Ctrl+Shift+N( z +Shift+N on the Mac) and then choose Layer New Background From Layer.

In Figure 5-10, another image was introduced as the background. Next, two different outer glow effects were added to the mountains and the moon. You may also have noticed that the moon looks somewhat transparent. This is because the moon layer's blend mode is set to Screen. Blend modes are covered in detail in the Chapter 6, and layer effects like Outer Glow are covered in Chapter 7.

image from book
Figure 5-10: A new background sky was added behind the mountains, and then outer glows were added to both the mountains and the moon to create a more preternatural feel.

Photoshop permits only one background layer per image. If an image already contains a background layer, the command Layer New Background From Layer changes to Layer From Background, which converts the background layer to a floating layer, as when you double-click the Background item in the Layers palette.

Reordering layers

What good are layers if you can't periodically change what's on the top and what's on the bottom? You can reorder layers in two ways. First, you can drag a layer name up or down in the scrolling list to move it forward or backward in layering order. The only trick is to make sure that the black bar appears at the point where you want to move the layer before you release the mouse button, as illustrated in Figure 5-11.

image from book
Figure 5-11: Drag a layer between two other layers to make the all-important black bar appear (left). Then release the mouse to change the layer's hierarchy (right).

The second way to reorder layers is to choose a command from the Layer Arrange submenu. For example, choose Layer Arrange Bring Forward to move the active layer up one level; choose Layer Arrange Send to Back to move the layer to above the background layer.

You can move faster if you remember the following keyboard shortcuts:

  • Ctrl+Shift+] (Win) or z +Shift+] (Mac): Press Ctrl+Shift+right bracket (Win) or z +Shift+right bracket (Mac) to move the active layer to the top of the stack.

  • Ctrl+Shift+[ (Win) or z +Shift+[ (Mac): This shortcut moves the active layer to the bottom of the stack, just above the background layer.

  • Ctrl+] (Win) or z +] (Mac): This nudges the layer up one level.

  • Ctrl+[ (Win) or z +[ (Mac): This nudges the layer down.

    Note  

    You can neither reorder the background layer nor move any other layer below the background until you first convert the background to a floating layer, as explained earlier in the "Modifying the background layer" section.

Displaying layer edges

When layer content is really tiny, or is right next to, slightly behind, or mostly obscured by other content, it can be hard to spot it and even harder to click on it with your mouse to move it. To make your layers easier to see and click on, no matter how small, see-through, or camouflaged they may be, Photoshop CS2 offers the View Show Layer Edges command. To use this feature, first click the layer you want to see highlighted by an edge (use the Layers palette to click on it). Then choose View Show Layer Edges to display the dark blue box you see in Figure 5-12.

image from book
Figure 5-12: Turn on Layer Edges to display a helpful box that surrounds the active layer.

After you turn this option on, whichever layer you activate ” be it by selecting the layer by clicking on it in the Layers palette or by clicking the layer content directly with your mouse ” will be encompassed by that blue box. If you use the Shift or Ctrl (Cmd on the Mac) keys to select multiple layers, each of the selected layers is encompassed by its own box.

To turn those boxes off, you can either reselect the command to toggle it off, or turn off the view of all Extras (guides, slice borders, and so on) with the View Extras command. This latter approach is rather radical , unless you want to eliminate all visual clutter in one sweeping command. To tweak which things to show and not show, use the View Show submenu to click on and off those features you want to see.

Blending layers

Photoshop lets you blend layers like no other program in the business. In fact, Photoshop does such a great job that it takes an entire chapter ” Chapter 6 ” to explain these options in detail. This section serves as an introduction so that you're at least aware of the basics. If you have bigger questions, Chapter 6 is waiting to tell all.

The Layers palette provides four basic ways to blend pixels between layers (see Figure 5-12). None of these techniques permanently changes as much as a pixel in any layer, so you can always return and reblend the layers at a later date.

  • The Opacity value: Enter a value in the Opacity option box near the top of the Layers palette to change the opacity of the active layer or floating selection. If you reduce the Opacity value to 50 percent, for example, Photoshop makes the pixels on the active layer translucent, so the colors in the active layer mix evenly with the colors in the layers below.

    Tip  

    If any tool other than a paint or an edit tool is active ” including the selection and navigation tools ” you can press a number key to change the Opacity value. Press 1 for 10 percent, 2 for 20 percent, up to 0 for 100 percent. Or you can enter a specific Opacity value by quickly pressing two number keys in a row. For example, press 3 and then 7 for 37 percent.

  • The Fill value: The Fill option lets you adjust the opacity of pixel information in the layer ” anything painted , drawn, or typed ” without affecting the opacity of any layer effects that might be applied. For example, if you have a text layer with the Drop Shadow layer effect applied, lowering the Fill slider to 0 fades out the text itself, leaving just the ghostly drop shadow behind. As with all other blending- related options, the Fill option is explained in excruciating detail in Chapter 6.

  • The blend mode pop-up menu: Choose an option from the blend mode popup menu ” open in Figure 5-13 ” to mix every pixel in the active layer with the pixels below it, according to one of several mathematical equations. For example, when you choose Multiply, Photoshop really does multiply the brightness values of the pixels and then divides the result by 255, the maximum brightness value. Blend modes use the same math as the brush modes covered in Chapter 1. In fact, the two terms are sometimes used interchangeably. But you can accomplish a lot more with blend modes, which is why they get so much attention in Chapter 6.

    image from book
    Figure 5-13: The blend mode pop-up menu and the Opacity and Fill option boxes enable you to mix layers without making any permanent changes to the pixels.

    Tip  

    As with Opacity, you can select a blend mode from the keyboard when a selection or navigation tool is active. Press Shift+plus to advance incrementally down the list; press Shift+minus to inch back up. You can also press Shift+Alt (or Shift+Option on the Mac) and a letter key to select a specific mode. For example, Shift+Alt+M(Shift+Option+M) selects the Multiply mode. Shift+Alt+N (Shift+Option+N) restores the mode to Normal. Note that because many of the key choices are not as logical or easily remembered as N for Normal or M for Multiply, you'll want to remember the Shift+ plus and Shift+minus technique discussed here, if only to avoid having to remember the keys associated with all the individual blend modes.

  • Blending Options: Choose Layer Layer Style Blending Options or double- click a layer thumbnail to display the Layer Style dialog box. The General Blending area of this dialog box provides access to a Blend Mode pop-up menu and an Opacity value, but it also offers a world of unique functions. As discussed in Chapter 6, you can hide one or more color channels, specify which colors are visible in the active layer, and force other colors to show through from the layers behind it. Select an item from the left-hand list to apply a layer style, as discussed in Chapter 7.

Although far short of the whole story, that should be enough to prepare you for anything thrown at you throughout the remainder of this chapter.

Fusing several layers

Although layers are wonderful and extremely helpful devices, they have their drawbacks ” of course, none of these negative aspects outweighs their usefulness . Layers do expand the size of an image in RAM and ultimately lead to slower performance; and as noted in Chapter 3, only four formats ” PDF, TIFF, the new PSB, and the native PSD ” permit you to save layered compositions. You can use layers in the construction of any image. It's just that when you go to save it in any format other than those four, your layers will be combined into a single layer, and further editing on an individual layer basis will be impossible . Of course, you can save a PSD or TIFF version of the artwork too, and that way you'll retain an editable, layer- laden copy.

With the size and performance- eating problem in mind, you may want to put your image on a diet of sorts. To slim down your image, Photoshop provides the following methods for merging layers:

  • Merge Layers (Ctrl+E or z +E): Choose Layer Merge Layers to merge two or more selected layers.

    Photoshop CS2  

    This is a slight change from Photoshop CS, which had more merging options in terms of how the Merge commands appeared in the Layers menu. For example, if you had linked layers and went to the Layers menu, the command appeared as"Merge Linked." Now it appears as "Merge Layers," and Photoshop assumes you mean to merge the layers you have selected at the time.

  • Merge Visible (Ctrl+Shift+E or z +Shift+E): Choose the Merge Visible command to merge all visible layers into a single layer. If the layer is not visible ” that is, if no Eye 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. Photoshop does not give this command a keyboard shortcut because it's so dangerous. To take a safer, more conservative route, you may want to flatten an image incrementally using the two Merge commands ” whittling away at the number of layers until you're ready to merge them all into one.

    Caution  

    Note that Photoshop asks whether you want to flatten an image when converting from one color mode to another. You can choose not to flatten the image (by pressing D or clicking the Don't Flatten button) but this may come at the expense of some of the brighter colors in your image. As discussed in Chapter 13, many of the blend modes perform differently in RGB than they do in CMYK.

    image from book
    Duplicate and merge, all in one step

    To simultaneously merge and duplicate two or more selected layers, press Alt when applying either the Layer Merge Layers or Layer Merge Visible commands. Pressing Alt (Win) or Option (Mac) and choosing Merge Layers ” or pressing Ctrl+Alt+E ( z +Option+E on the Mac) ” clones the contents of the selected layer/s into the layer below it. Pressing Alt (Win) or Option (Mac) and choosing Merge Visible ” or pressing Ctrl+Shift+Alt+E ( z +Shift+ Option+E on the Mac) ” copies the contents of all visible layers to the active layer. The resulting layer in either case will have the word merged in parentheses following the name of the topmost layer that was included in the merge. The History palette lists the action as Stamp Layers ” something handy to know in case you want to go back and undo this. More useful is the ability to copy the merged contents of a selected area. To do so, choose Edit Copy Merged or press Ctrl+Shift+C ( z +Shift+C on the Mac). You can then paste the selection into a layer or make it part of a different image.

    image from book
     

Deleting layers

You can also merely throw a layer away: drag the layer name onto the Trash icon at the bottom of the Layers palette, or click the Trash icon to delete the active layer. Or, right-click the layer to be deleted and choose Delete Layer from the pop-up menu. So many choices.

Tip  

When you click the Trash icon, Photoshop displays a message asking whether you really want to toss the layer. To give this message the slip, Alt+click (orOption+click) the trash can icon.

Tip  

Here's a much juicier tip for you: If the active layer is linked to one or more other layers (see the upcoming section "Moving, Linking, and Aligning Layers"), you can delete all linked layers in one fell swoop by Ctrl+clicking the Trash icon (that's z +clicking on the Mac).

Saving a flattened version of an image

As mentioned earlier, only four file formats ” PDF, TIFF, PSB, and the native Photoshop format ” save images with layers. If you want to save a flattened version of your image ” that is, with all layers fused into a single image ” in some other file format, choose File Save As or press Ctrl+Shift+S ( z +Shift+S on the Mac) and select the desired format from the Format pop-up menu. If you select a format that doesn't support layers ” such as JPEG, GIF, or EPS ” the program dims the Layers check box.

The Save As command does not affect the image in memory. All layers remain intact. And if you select the As a Copy check box with the Layers option deselected ” which is a good idea ” Photoshop doesn't even change the name of the image in the title bar. It merely creates a flattened version of the image on disk. Nevertheless, be sure to save a layered version of the composition as well, just in case you want to edit it in the future.



Photoshop CS2 Bible
Photoshop CS2 Bible
ISBN: 0764589725
EAN: 2147483647
Year: 2003
Pages: 95

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