Using Layers in Photoshop -- Part I

Article and Photography by Ron Bigelow

www.ronbigelow.com

Photoshop CS or Photoshop CS2 Used in this Tutorial

Layers is one of the most basic aspects of Photoshop (as well as other image editing programs). Yet, it is also one of the most powerful. While simplistic in nature and application, the use of layers opens the door to advanced editing capability that would be extremely difficult, if not impossible, without layers. Thus, a solid understanding of layers is a prerequisite for the development of more advanced image editing skills.

What are Layers

At the most simplistic level, layers are nothing more than layers, or planes, of information. Each layer contains specific information and has a specific purpose. For instance, a simple image might have the following layer structure:

Layer 5: Sharpening.
Layer 4: Saturation adjustment.
Layer 3: Tonal adjustment.
Layer 2: Color cast adjustment.
Layer 1: The original image.

As can be seen, each layer has a different purpose.

Figure 1: Image that Utilizes Layers

Layers are managed in the Layers palette. Anytime a new image is created in Photoshop, a Layers palette is created for that image. Anytime an existing image is opened in Photoshop, the Layers palette is available for that image. If the Layers palette is not open, it can be accessed by choosing Windows/Layers. Figure 1 shows an image that was edited with layers. Figure 2 shows the Layers palette for this image.

Figure 2: Layers Palette

This image has fourteen layers, each optimized for a specific effect (in Photoshop CS2, the number of layers that can be added is limited only by the computer that is being used to edit the image).

Each layer covers the layers below it. What can be seen depends on the type of area that is being viewed in a layer. Each layer can have up to three types of areas (the area type is determined by masks and Blend Modes):

Opaque areas: These areas are not transparent. Therefore, the only thing that is seen is whatever is on this layer. The lower layers are not seen at all.
Transparent areas: These areas are completely transparent. In other words, what is seen in transparent areas is actually from the lower layers.
Semitransparent areas: In semitransparent areas, part of what is seen is from the layer and part is from the lower layers.

When an image is viewed, it is viewed from the top layer down. So, in areas where the top layer is opaque, the viewer will see only the top layer. The effects of the lower layers will not be seen. In areas where the top layer is transparent or semitransparent, the viewer will see the effects of the next to the top layer. In areas where both the top two layers are transparent or semitransparent, the viewer will see the effects of the next layer down. This continues down to the bottom layer.

Why Use Layers

The first question that should be asked about layers is, "Why should we even bother with layers?" After all, the image editing could simply be done on the original image layer. Then, the image would have only one layer. While this might sound much simpler than using multiple layers, utilizing layers provides six major benefits.

Ability to Rework Previous Edits: With layers, a photographer can go back and rework previous edits. For instance, assume that a sharpening layer was created at some point. Subsequently, several other edits were made (each on its own layer). If the photographer later decided that the sharpening was too strong, she could simply go back and change the sharpening layer to reduce the amount of sharpening. On the other hand, if layers were not used and the sharpening was done on the original image, the sharpening was essentially burned into the image. It could not be modified. The photographer will either have to use the History palette to go back before the sharpening step and redo all of the work from that point, or she can delete the image and start over. Neither option is very attractive.
Independence of Edits: Each layer is independent of the other layers (unless specific layers are purposely modified to be dependent on each other). Therefore, the edits on any one layer are independent of the edits on other layers. In other words, each layer can be modified without affecting any of the other layers in the image. For instance, a saturation layer could be added to an image. If it was later decided to modify the saturation, or to remove it completely, that could be done without the other layers being affected.
Flexibility: The use of layers adds tremendous flexibility: the order of the layers (and therefore the edits) can be changed, the transparency of areas can be altered, layers can be turned off and then back on again, the blend modes of the layers can be switched, and much more.

Image Quality: The use of layers can significantly improve the quality of an image. Most image edits (e.g., applying Levels, Curves, Hue/Saturation, and sharpening) create some degree of image degradation. In most cases, the image degradation associated with a single edit is small and will not be noticed. The problem is that most images need many different edits. For example, the image shown in Figure 1 needed fourteen edits (as shown in the Layers palette in Figure 2) to be ready for interpolation and final sharpening (which added additional edits). Now, if layers were not used, this image degradation would occur each time an edit was completed. So, if fourteen edits were made without the use of layers, the image would be degraded once for each edit. As a result, the image would be degraded fourteen times. This would create cumulative damage to the image, which may very well be significant enough to be noticed in the final image. On the other hand, when layers are used, the image degradation only occurs when the image is either flattened or printed. Then, all of the edits are applied at once. Consequently, the image is degraded only once. This results in less image degradation and higher quality prints.
Organization: Layers can be used to facilitate the organization of the image editing. As an example, all of the tonal corrections could be put into one layer set (layer sets will be covered later), the color corrections in a second layer set, and the sharpening in yet a third layer set. For images with a large number of edits, this can simplify the editing. If at a later time a photographer decides that a change needs to be made to one of the tonal correction layers, he can quickly locate that layer in the tonal correction layer set and make the changes.
Effects: Layers allow effects that could not be done without layers. The use of Blend Modes and advanced blending options, for instance, are not possible without the use of layers.

In short, the use of layers opens up vast capabilities in the area of image editing.

The Downside of Layers

There is one downside to layers; each layer increases the file size. Therefore, unnecessary layers should be avoided (e.g., delete layers if it is determined that they are no longer needed.

Types of Layers

There are many types of layers. Each has its own uses, advantages, and limitations. The first step in mastering layers is to understand the various types of layers.

Types of Layers: Background Layer

Figure 3: New Image

Anytime a new image is opened in Photoshop, the image is created as a Background layer. Figure 3 shows a new image that was just opened but has not yet been edited. Figure 4 shows that the image has been opened as a Background layer in the Layers Palette.

Figure 4: Background Layer of New Image

There can only be one Background layer in an image. The Background layer can not be moved; neither can the Blend Mode or Opacity be changed (unless the Background layer is converted into a regular layer). The Background layer is a special layer. It contains the original image data. It is best not to perform any edits on this layer. That way, the original image data remains untouched. Edits should be performed on other layers that can be added during the editing process.

Types of Layers: Adjustment Layers

Figure 5: Create New Fill or Adjustment Layer Button on the Layers Palette

Adjustment layers allow tonal or color edits to be made to an image. In Photoshop CS2, there are twelve adjustment layers: Levels, Curves, Color Balance, Brightness/Contrast, Hue/Saturation, Selective Color, Channel Mixer, Gradient Map, Photo Filter, Invert, Threshold, and Posterize (it is beyond the scope of this article to go into each of these adjustment layers).

Adjustment layers can be added to an image by choosing Layer/New Adjustment Layers. The appropriate adjustment layer can then be chosen from the menu. Another option is to click on the Create new fill or adjustment layer button on the Layers palette (see Figure 5).

Once an adjustment layer has been added, tonal or color edits can be made with that layer.

Figure 6: Curves

An example of an adjustment layer is a Curves layer (see Figure 6). Figure 7 shows the Curves Adjustment layer after it was added to the image in Figure 3.

Figure 7: Curves Adjustment Layer in the Layers Palette

Types of Layers: Image Layers

An Image layer is any layer that contains image data. An image layer can be created in a number of ways (e.g., image data pasted from another layer or an image layer dragged over from another image).

Figures 8 -- 10 show how an image layer can be used. Figure 8 shows the original image seen earlier. To improve the quality of the image, it was decided to lighten up the detail in the ocean; so, a lighter copy of the image was converted from the raw file (see Figure 9). This layer was then dragged over to the original image. Figure 10 shows the Layers palette with the new, image layer (the lighter copy of the image). Further work with masks and blending modes will allow the ocean to be lightened a bit by utilizing the added image layer.

Figure 8: Original Image

Figure 9: Lighter Copy of the Image

Figure 10: Layers Palette with New Image Layer

Types of Layers: Empty Layers

An Empty layer is a layer that is just that -- empty. It has no image data, and it contains no tonal or color edits. It may seem a little bit odd to add Empty layers to an image. After all, Empty layers do not change the image in any way. However, an Empty layer provides a layer where further editing can be done.

Figure 11: Create a New Layer Button on Layers Palette

An Empty layer can be added to an image by choosing Layer/New/Layer or by clicking on the Create a new layer button on the Layers palette (see Figure 11). Figure 12 shows the Layers palette with an Empty layer added.

Figure 12: Layers Palette with Empty Layer

Figure 13: Empty Layer after Image Data Was Pasted

Figures 13 and 14 show one use of an empty layer. As mentioned previously, the ocean in this image needs to be lightened up somewhat. One approach is to select the ocean in the background layer, copy the selection, create an empty layer, and paste the ocean selection into the empty layer. The ocean can then be edited on this layer. Figure 13 shows the Empty layer after the selection of the ocean was pasted (of course, this layer is no longer an empty layer; it is now an Image layer). Figure 14 shows the Layers palette after these actions were performed.

Figure 14: Layers Palette with Empty Layer after Data Was Pasted

Types of Layers: Neutral Layers

A Neutral Layer is a layer that is filled with neutral gray. Like an Empty layer, A Neutral layer, initially, has no image data and contains no tonal or color edits. However, again like an Empty layer, a Neutral layer provides a layer where further editing can be done.

One of the easiest ways to create a Neutral layer is to choose Layer/New/Layer. The New Layer Dialog Box will appear (see Figure 15). In the dialog box, the Use Previous Layer to Create Clipping Mask option should be unchecked. The color should be set to None and the Opacity to 100%. When the dialog box first appears, the Mode will be set to Normal. With this setting, the Fill with Overlay-neutral color option will be grayed out and can not be selected. In order to create a neutral layer, one of the other Modes that will activate this option, such as Overlay, will need to be selected. Then, the Fill with Overlay-neutral color option is checked. Clicking OK will create the new layer, which will now be found in the Layers palette (see Figure 16).

Figure 15: New Layer Dialog Box

Figure 16: Layers Palette with Neutral Layer

Figure 17: Neutral Layer

Figures 17 and 18 shows a use for a Neutral Layer. Figure 17 shows the Neutral layer after the Dodge tool was used to dodge the Neutral layer in order to lighten the ocean. Figure 18 shows the Layers palette after these actions were performed.

Figure 18: Layers Palette with Neutral Layer after Dodging Action

Types of Layers: Fill Layers

A Fill layer is a layer that is filled with a solid color, a gradient, or a pattern. These layers are often used for creating special effects.

Figure 19: Create a New Fill or Adjustment Layer Button on Layers Palette

A fill layer can be added to an image by choosing Layer/New Fill Layer or by clicking on the Create a new fill or adjustment layer button on the Layers palette (see Figure 19). A menu will allow a Solid Color, Gradient, or Pattern layer to be chosen. A couple of dialog boxes will provide several more options. These options vary depending on which type of layer is chosen and the desired effect that is being created (the proper selection of these options for various effects is beyond the scope of this article). Figures 20 -- 22 show examples of the three types of Fill layers.

Figure 20: Solid Color Fill Layer

Figure 21: Gradient Fill Layer

Figure 22: Pattern Fill Layer

Types of Layers: Duplicate Layers

A Duplicate layer is simply a layer that has been created by duplicating another layer.

Figure 23: Create a New Layer Button on Layers Palette

A Duplicate layer is created by selecting the layer that is to be duplicated and choosing Layer/Duplicate Layer and completing the Duplicate Layer dialog box or by simply dragging the layer down to the Create a new layer button at the bottom of the Layers palette (see Figure 23). Figure 24 shows the Layers palette with the Background layer duplicated. This duplicated layer can now be used for image editing without altering the original image data in the Background layer.

Figure 24: Layers Palette with the Background Layer Duplicated

Types of Layers: Text/Line Layers

A Text layer is a layer that contains text and a Line layer is a layer that contains a line or arrow.

Figure 25: Type Tool on Tools Palette

A Text layer is created by selecting one of the Type tools from the Tools palette (see Figure 25) and clicking on the image. The text can then be typed. The formatting and placement of the text can be edited as desired.

Figure 26: Image with Text Added

Figure 26 shows an image with a Text layer added. Figure 27 shows the associated Layers palette.

Figure 27: Layers Palette with Text Layer

A Line layer is created by selecting the Line tool from the Tools palette (see Figure 28) and drawing the line on the image. The formatting and placement of the line can be edited as desired.

Figure 28: Line Tool on Tools Palette

Figure 28, which is used to illustrate the Line tool, is a good example of an image with a line added. In this case, the image was a graphic that needed a line for illustrative purposes. Figure 29 shows the associated Layers palette (since this image is a graphic created in Photoshop, rather than an image that is opened in Photoshop, there is no Background layer).

Figure 29: Layers Palette with Line Layer