10. Creating Layer and Channel Masks

When you work on documents in Adobe Photoshop, the application does its best to make the experience as similar to the real world as possible. When you select the Brush tool and drag the document, you expect to see a swath of color using the pre-selected size and brush tip. That’s what you expect to see when you drag a brush on a canvas, and that’s what you see in Photoshop. Creating a realistic experience is what Photoshop is all about. Yet, as realistic as the Photoshop experience is, there are elements of digital design that go way beyond the real world. For example, something as simple as the ability to undo. Photoshop has an undo button, life does not. Layer masks give you the ability to remove elements of a layer without actually erasing the image pixels. Layer masks fall into the area of Photoshop called “controlling the image.” If you can control what elements of an image are visible, without erasing, you have control. In addition, layer masks are editable, which means you can change your mind at any time during the creative process.

Imagine creating a complicated selection in Photoshop. You will probably use several of Photoshop’s selection tools and by the time you’re finished (or almost finished) you have selection marquees all over the document. Traditional selections are temporary; they last only as long as your document is open. But what if you want to save this selection for use later in the design? What you need is a channel mask. Channel masks hold simple, or complicated selections, and can be saved with the document. Channel masks are created from pre-existing selections, or can be created from scratch by painting the mask with black, white, or shades of gray. The process of creating a Channel mask is simple, but the results are powerful.

Understanding the Role of Layer Masks

PS 3.4

Layer masks are not new; however, Photoshop designers find new ways to use them every day. A layer mask is an attachment to a layer that defines the visible elements of the layer. Each layer type in Photoshop, with the exception of the Background, has the ability to hold a layer mask. Imagine a layer mask as a piece of paper laying directly over the image, and then take a trimming blade and cut holes in the paper. The holes in the paper represent the visible elements of the image, while the other areas of the image become transparent. Each layer in a multiple layered document has the ability to hold its own mask, and the mask only influences the image elements of the layer it’s attached. Once a mask is created, it can be modified using any of Photoshop’s painting or drawing tools. Black represents transparent elements, and white represents visible elements. Painting with a shade of gray introduces a level of transparency. For example, painting with 50 percent gray, makes the image pixels appear 50 percent transparent.

Creating a Layer Mask

PS 3.4

The creation of a layer mask requires two things: an open document and any Photoshop layer type with the exception of the Background. When you add the layer mask, you will be working with two layer elements—the image and the mask. It’s important to know what element you’re working on, or you might wind up painting on the image instead of the mask. When that occurs, it’s good to remember the undo button. Once the mask is created, you can selectively control, without erasing, the visible portions of the image.

Create a Layer Mask

Open a document.

Click the Layers palette.

Click the layer to contain the mask.

Click the Add Layer Mask button.

Click on the image thumbnail to modify or adjust the image.

The active pointer resembles a brush, indicating you are working on the image.

Click on the mask thumbnail to modify or paint the mask.

The active pointer resembles the mask button, indicating you are working on the mask.

Click the chain button to separate the mask from the image.

This allows you to move the mask, without moving the image, or vise versa.

Click the chain button again to reestablish the link between mask and image.

Shift+click on the mask button to temporarily disable or enable the mask.

Alt+click (Win) or Option+click (Mac) to view or hide the mask in the document window.

Working with the Paint Tools

Unless a mask is created using a selection, layer masks begin their lives as pure white. The reason a created layer mask does not appear to have any visible effect on the image, is that the color white indicates the visible areas of the image. It’s only when you begin painting on the mask does the image change. You create transparency in the image by painting in shades of gray. The deeper the shade of gray, the more transparent the image. Painting the mask with pure black produces 100 percent image transparency. Any of Photoshop’s drawing or painting tools can be employed to create the mask. In fact, you could even use the custom shape drawing tools and create a mask in the shape of a rubber duck. The trick is to use the right tools to create the right effect. For example, using a hard edge brush creates an image with sharp edges and using a soft-edge brush creates an image where the visible edges of the image blend smoothly with transparent elements.

Work with the Paint Tools

Open a document.

Create a layer mask on one of the active image layers.

Click the layer mask thumbnail.

Select the Brush tool and brush tip.

Move into the document window and paint, and then use black to create transparency.

Use white to touch up the image.

Use shades of gray to create partial transparency.

Using Selections to Generate Complex Layer Masks

Layer masks are easy to create, you select a layer and then click the Add Layer Mask button. Unfortunately, when you create a mask this way, it’s up to you to define the transparent areas, using drawing or painting tools. There is another way to generate a mask, and that’s through selection. When you click the Add Layer Mask button, Photoshop searches the document for any selected areas. If it doesn’t find any, it creates a blank (all white) mask. However, if you first select an area or areas of the image, Photoshop interprets the selection as the area you want to remain visible.

Use Selections to Generate Masks

Open a document.

Select the areas of the image you want to preserve.

Click the Add Layer Mask button.

Photoshop generates a layer mask based entirely on your selection.

Did You Know?

You can apply layer styles to a masked image. Create the mask, and then click the Add Layer Style button, located at the bottom of the Layers palette. Then use any of Photoshop’s layer styles, such as Drop Shadow, or Bevel And Emboss. The layer style will only be applied to the visible portion of the image.

Using Layer Masks to Generate Soft Transparency

When you create a layer mask using Photoshop’s selection tools, the edges of the image where transparency occurs appear as if cut out with a knife. This occurs because selection tools create knife-edge selections, and then when you create the layer mask, the edges appear as ragged as the mask. You can click the Selection menu, click Refine Edge, and then adjust the Feather to soften the effect of the selection; however you won’t be able to determine the effects of your Feather option until you create the mask. Many times this technique turns into a guessing game, with you creating mask after mask, until you see what looks best. A better way to work is create the hard mask, and then visually create a softer mask using a Photoshop filter named Gaussian Blur. Since the Gaussian Blur filter has the ability to preview the blur before applying, you have the perfect tool to create visually pleasing results.

Use Layer Masks for Transparency

Open a document.

Create a selection around the area you want to preserve.

Click the Select menu, and then click Refine Edge.

Drag the slider to select a Feather Radius value (1 to 250). The greater the value, the greater the feathering effect.

Click OK.

Click the Add Layer Mask button.

The Layer mask uses the Feather option to soften the visual effect of the mask.

Blending Images with Layer Masks

Layer masks make areas of an image appear transparent by painting with black. Then just as quickly, you can make those areas reappear by painting with white. There are obvious applications to the use of layer masks—changing a sky, removing a tree, or even removing a person who was cut off in the photo. For example, you have an image, and you want the image to change from line art to a normal photograph. To accomplish this, you’ll need a copy of the image in a separate layer, a layer mask, and the linear gradient tool.

Blend Images with Layer Masks

Open a document.

Select the layer you want to use for the effect in the Layers palette. If this is a multi-layered document, this layer should be at the top of the layer stack.

Drag the layer over the Create New Layer button to make a copy.

Timesaver

If making a copy of a layer is a common practice, press Ctrl+J (Win) or +J (Mac).

Click the Add Layer Mask button, and then add a layer mask to the copy layer.

Use any of Photoshop’s adjustment or filter effects to make changes to the copy.

Select black and white for the default foreground and background colors.

Select the Gradient tool, and then select a linear gradient using the foreground to background gradient option.

Click the layer mask thumbnail in the copy layer.

Drag the Gradient tool, left to right, across the document.

The image slowly goes transparent from left to right, exposing the original image.

Using a Layer Mask to Create a Vignette

When you open a document in Photoshop, the image displays in a standard bounding-box format; a square or rectangle with 90-degree corners. Bounding boxes serve a purpose, and many times a nice square or rectangle box is exactly what you want. But let’s face it, bounding boxes can be a bit boring, especially when you want to spice up that image with a nice soft vignette. To create a soft vignette, you need four things—an image, a selection, a layer mask, and a Gaussian Blur filter.

Create a Vignette

Open a document.

Select the Elliptical Marquee tool, and then create an oval selection in the document. The Ellipse should contain the area you want to preserve.

Click the Add Layer Mask button in the Layers palette.

Click the layer mask thumbnail.

Click the Filter menu, point to Blur, and then click Gaussian Blur.

Drag the Radius slider right or left to increase or decrease the amount of blur applied to the mask.

Select the Preview check box, and then watch the live preview until you see the correct amount of blurring applied to the layer mask.

Click OK.

Creating Unique Layer Mask Borders

Layer masks can create more than simple vignettes around an image. In fact, with the right filters you can create some very interesting and fun-looking borders. For example, when you create a selection using one of Photoshop’s standard selection tools—rectangle, ellipse, or lasso—the selection has a sharp, definable border. The secret to creating unique borders is to create a general selection around a portion of the image you want to preserve, create the layer mask, and then use some of Photoshop’s creative filter effects, such as the Artistic or Distort filters on the mask. Using filters on the image mask creates eye-catching borders, and it’s only a filter away.

Create a Layer Mask Border

Open a document.

Click the layer you want to use in the Layers palette to apply a unique border.

Create a rectangular selection around a portion of the image.

Click the Add Layer Mask button.

Click the layer mask thumbnail.

Click the Filters menu, point to Brush Strokes, and then click the Sprayed Strokes filter.

Adjust the filter options to change the edge of the layer mask.

Click OK.

Did You Know?

You can apply more than one filter to a layer mask border. For example, using the Spatter filter creates a ragged edge to the layer mask. Applying a small amount of Gaussian Blur to the mask softens the effect and creates a more pleasing visual transition between the mask and the background.

Understanding Channel Masks

The Channels palette serves three purposes—to hold color information, to hold spot color information, and to hold selections (channel masks). Creating channel masks can be as easy as clicking the Create New Channel button, and then using any painting or drawing tools to create the mask, or by making a selection, and converting the selection into a mask, by clicking the Convert To Mask button. When you paint the channel mask, the defaults are—black for masked areas, white for selected areas, and shades of gray for percentages of selection.

Use Channel Masks

Open an image.

Select the Channels palette.

Click the Create New Channel button.

Select the new channel.

Select the Brush tool on the toolbox, and then select a brush tip on the Options bar.

Paint areas of the mask white to create a selection.

Paint areas of the mask black to mask the image.

Did You Know?

You can quickly convert a Channel mask into a selection. To view a Channel mask as a selection, open the Channels palette, and then Ctrl+click (Win) or +click (Mac) on the channel. Photoshop instantly translates the black, white, and gray areas of the mask into a visible selection in the document window.

Creating Channel Masks from Scratch

Channel masks are easy to create and once created, are just as easy to modify. All you need is an open document, and access to the Channels palette. By selecting a painting or drawing tool, you paint the mask to define the selection area. The problem is you can’t see the image, you only see the mask. What you need is the ability to view the mask and the image, almost like a piece of tracing paper, and then use the drawing tools to paint (trace) the portions of the image you want to select. The secret to viewing the image as you create the mask is to temporarily enable or show, the composite channel. In fact, the composite channel acts like a toggle switch—when it’s showing, you see the image and the mask like tracing paper, when it’s hidden you only view the mask.

Create Channel Masks

Open an image.

Select the Channels palette.

Click the Create New Channel button.

Click the Show/Hide button on the composite channel. The image is revealed in the document window (the new Alpha channel should still be selected). You will use the image to guide the creation of the mask.

Select the Brush tool on the toolbox.

Paint areas of the image using white to create a selection (painting with white, exposes the original image).

Paint areas of the image black to mask the image (painting with black, masks the image with a default color of red).

Click the Show/Hide button on the composite channel. The image is hidden revealing just the mask.

Repeat steps 6-8 until the mask is complete.

Modifying Channel Mask Options

Channel masks have default options that control how the mask looks and functions. Photoshop gives you the ability to change the default options of a channel mask. For example, you could change the default color from red to blue, or you could change the function of the channel mask from selection to spot color. Knowing you can change the mask options gives you more control over the final results.

Modify Channel Mask Options

Open a document.

Select the Channels palette.

Click the Channels Options button, and then click New Channel.

Enter a name for the new channel.

Click the option to define the mask color as the Masked Areas, Selected Areas, or Spot Color.

Click the Color box, and then select a color from the Color Picker.

Enter an Opacity percentage value (1 to 100) for the color.

Click OK.

Did You Know?

You can change the Channel options for a pre-existing channel. Double-click on the channel, and Photoshop will open the Channel options dialog box.

You can set Channel options for each channel. Changing the Channel options only impacts that specific channel. Each channel can have its own individual settings.

Creating Channel Masks from Selections

PS 4.2

Creating Channel masks from scratch (using brush and drawing tools) is a useful feature, and gives you the ability to create a mask in any desired size or shape. However, there are times when it would be easier to first define the areas you want to save, and then create the mask. When you create a Channel mask from an existing selection, Photoshop uses the selected areas to create the mask. For example, you have an image of a woman wearing a red dress, and you want to change the color of the dress to green. The first step would be to select the red dress. Rather than create a new mask, and paint out the area representing the dress, it would easier to first use a tool like the Magic Wand, select the dress, and then convert the selected area (the dress) into a Channel mask. Once the mask is created, you could fine-tune the mask, using Photoshop’s painting tools, and then change the dress color. Whether you create a mask from scratch or choose to create one through a pre-defined selection depends on the image, and what you’re trying to accomplish.

Create Channel Masks from Selections

Open a document.

Create a selection using any of Photoshop’s traditional selection tools.

Select the Channels palette.

Click the Save Selection As Channel button.

Photoshop creates a new channel mask based on the selected areas of the document.

Making Channel Masks from Native Color Channels

Creating a channel mask from a native color channel, takes a few steps; however, if you’re successful the effort spent making the selection is well worth it. The trick to creating a mask with a native color channel is to use the shifts of gray in one specific color channel to create the black and white areas characteristic of a typical channel mask. For example, you have an image of a model, and you want to remove the model from the background. Unfortunately, that requires selecting around the model’s hair, a difficult thing to accomplish, even in the best of circumstances. To make the channel mask, open the Channels palette and examine the native color channels, one at a time. You’re looking for a color channel that displays a significant shift of gray between the model’s hair, and the background. For example, you click on the red channel of an RGB image, and the models hair appears dark gray, while the background appears light gray. The difference is so pronounced you can actually see individual strands of hair, standing out against the background. If you can find such a contrast, you can quickly make a channel mask.

Make Channel Masks from Native Color Channels

Open a document.

Click the Channels palette.

Click and view the individual native color channels one at a time.

Click the channel that best represents a visual difference between what you want to select and what you want to mask.

Drag the selected channel over the Create New Channel button.

Photoshop makes a copy of the selected native color channel.

Click the native color channel copy.

Click the Image menu, point to Adjustments, and then click Threshold.

Move the Threshold slider left or right until you see a sharp black and white image with the black and white representing the selected and masked areas of the image.

Click OK.

Use Photoshop’s painting tools with black and white to touch up the new mask.

Did You Know?

You can use native color channel masks to perform image correction. Channel masks created from native color channels can be used for more than creating a mask. For example, you have a photo where the shadow portions of the image are too dark. Correct the problem by creating a channel mask that selects just the darker portions of the image, and then use the mask to control the Levels or Curves adjustments to lighten the overexposed areas of the image.

Loading Channel Masks

PS 4.2

Once you create a channel mask, and you can have up to 28 separate masks in one document, the next step is to use the masks. To save the channel mask all you have to do is save the document in a format that supports channels, such as Photoshop’s native .psd format, or even the .tif format. The next time you open the document, your channel masks will be there. Deleting a channel mask is simple; just drag the channel mask over the Delete button, located at the bottom of the Channels palette, or select the channel mask you want to delete, and click the Delete button. However sooner or later, you’re going to want to do more than just save or delete—you’re going to want to use a channel mask. Using a channel mask involves a process of converting the mask back into a selection. It’s an easy step, but necessary to complete the process from mask to selection.

Load Channel Masks

Open a document that contains a channel mask, or create a new channel mask.

Click the Select menu, and then click Load Selection.

If more than one document is open, click the Document list arrow, and then select the document you want to use.

Click the Channel list arrow, and then click the channel you want to convert into a selection (native color channels do not appear in this list).

Select the Invert check box to instruct Photoshop to use the black areas of the mask (instead of the white areas) for the selection.

Select the Operation option you want to perform:

New Selection. Creates a new selection.
Add To Selection. Adds the channel mask to an existing selection.
Subtract From Selection. Uses the channel mask to subtract from an existing selection.
Intersect With Selection. Uses the channel mask to intersect, based on an existing selection.

Click OK.

For Your Information: Working with Channel Masks

Channel masks provide controls over the selected areas of an image. By default, the white areas of the mask represent the selected areas, and the black areas represent the masked areas. When a mask is applied to an image, the sharp black and white of the mask create a very sharp-edged selection. To soften the effect of the mask, click the Filters menu, point to Blur, and then click Gaussian Blur. Apply a small amount of blur (one or two pixels) to the mask. Now, when the mask is applied to the image, the Gaussian blur will soften the effects of the selection and create a visually softer transition.

Moving Channel Masks Between Documents

Once you create a channel mask in one document, it is possible to move that channel mask from document to document. While most channel masks are so specific to a particular document, it wouldn’t be practical to move them—a channel mask defining a selection of a tree line against a blue sky—many channel masks can be used over and over again. For example, a series of channel masks that create unique selection borders around an image. You spent a lot of time creating the borders, and you would like to apply those same border selections to other images. If that’s the case, then increase your efficiency by saving them as layer masks and moving them between documents. Not only will it save you a lot of time, but using selections more than once can add a sense of cohesiveness to a design.

Move Channel Masks Between Documents

Open a document that contains a channel mask.

Open a second document (this is the document you will move the mask into).

Position the two document windows side-by-side.

Click the document containing the channel mask.

Select the Channels palette.

Drag the channel mask from the Channels palette into the open document window of the second document.

Combining Channel Masks

Channel masks are simply selections, which are defined with black, white, and shades of gray. Once a channel mask is placed in the Channels palette, you can use Photoshop’s vast array of drawing and painting tools or filters. The Gaussian Blur filter can make a great enhancement to a channel mask. It’s even possible to combine the selection elements of two or more channels together, and in doing so, create an even more complicated mask.

Combine Channel Masks

Open a document that contains two or more channel masks.

Click the Channels palette.

Press Ctrl+click (Win) or +click (Mac) on one of the channel masks.

The white areas of the channel become a selection.

Press Shift+Ctrl+click (Win) or Shift+ +click (Mac) a second channel mask.

The white areas of the second channel mask are added to the previous selection.

Click the Save Selection As Channel button.

Photoshop takes the combined areas of the two channels and creates a new channel mask.

Using the Quick Mask Mode

Quick Mask Mode gives you the ability to create a selection using Photoshop’s painting and drawing tools, without creating a channel mask. For example, you’re creating a selection using traditional selection tools, and there’s a portion of the image you’re having difficulty selecting. Since this is a one-time selection, you don’t want to go to the trouble of creating a channel mask. The solution is to move into the Quick Mask Mode. Quick Mask Mode toggles between a selection and quick mask. When you enter Quick Mask Mode, any pre-existing selections are converted into a red mask, and changes to the mask are performed using painting tools. When you return to Standard Mode, the masked (painted) areas are converted into a selection. While quick masks are created the same way as channel masks, they’re temporary. It’s a quick way to create a one-time selection.

Use the Quick Mask Mode

Open a document.

Create a selection using any of Photoshop’s selection tools.

Click the Edit In Quick Mask Mode button to convert the selection into a red overlay mask (it’s a toggle button).

Select the Brush tool.

Paint with white to open up more selection areas.

Paint with black to mask the image, which by default is red.

Click the Edit In Standard Mode button to return to a standard selection (it’s a toggle button).

Toggle between Quick Mask and Standard modes until you create the perfect selection.

Did You Know?

You can convert a quick mask into a permanent channel mask. Create the quick mask, return to Standard Mode, select the Channels palette, and then click the Create Channel From Selection button.

Working with Quick Mask Options

When you work in the Quick Mask Mode, the color for the mask is red, the opacity of the mask is 50 percent, and the red mask represents the masked areas of the document. Photoshop set up the Quick Mask options as a default, but they can be modified. For example, it would be very difficult to view a red mask if you were working on a primarily red image, or you might want to increase or decrease the opacity of the mask. Photoshop lets you do this through mask options.

Work with Quick Mask Options

Double-click the Edit In Quick Mask Mode or Edit In Standard Mode button (it’s a toggle button).

Click the Masked Areas or Selected Areas option to instruct Photoshop whether to create a mask or a selection from the color areas of the mask.

Click the Color box, and then select a color from the Color Picker.

Enter an Opacity percentage value (0 to 100).

Click OK.

Important

Quick Mask options are program, not document specific. The changes made to the Quick Mask options remain set until you change them.

Did You Know?

Once you’ve created a Quick Mask selection, you can save it as a permanent Channel mask. Just return the screen to Standard mode, open the Channels palette, and then click the Save Selection As Channel button.

For Your Information: Using Quick Masks

One of the powerful features of a Quick Mask is you can use filters directly on the mask. Create a selection in the Quick Mask Mode, and then click the Filter menu and choose from Photoshop’s many filters, such as Brush Strokes, Blur, or Distort. When you click OK, the filter is applied directly to the Quick Mask. Then, when you return to Standard Mode, the effect of the filter is applied to the selection. Working with filters and quick masks gives you the option of creating highly complicated masks, without every using the Channels palette.

Modifying Selections with Quick Mask Mode

Photoshop represents selection using an animated single-pixel wide marquee, sometimes referred to as a crawling or marching ant marquee. Typically the enclosed or “marquee” area represents the working area of the document. Unfortunately, when selections become complicated you wind up with crawling ants marching all over the screen. While complicated selections are a part of the Photoshop designer’s life, they shouldn’t have to be hard to visualize or modify. Photoshop knows this and created the Quick Mask option. When you’re using Quick Mask, Photoshop displays the selected areas with a user-defined color and opacity. Then by using your painting tools, you can make quick work of modifying the selection.

Modify Selections with Quick Mask Mode

Create a selection using any of Photoshop’s selection tools.

Click the Default Colors button to default your foreground and background painting colors to black and white.

Click the Quick Mask button to enter Quick Mask mode.

By default the selected area remains clear and the unselected area becomes masked with a 50 percent red.

Select the Brush tool.

Add to the selection by painting the Quick Mask with white and black. In Quick Mask mode, painting with black produces 50 percent red, and painting with white opens up the original image.

Click the Edit In Standard Mode button to revert the image back to a normal selection marquee.

Continue using the Edit In Quick Mask and Edit In Standard Mode buttons until you achieve the desired selection.

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Table of Contents for 10. Creating Layer and Channel Masks

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