PICshopy: Layer Masking

Layer Masking

When working in Photoshop, you’ll often need to combine multiple images together into a new

composite image. Those original images, how-

ever, may have backgrounds or objects that you

no longer want. This is where Layer Masks come

in. Far superior to erasing pixels, Layer Masks

allow you to hide (or mask) part of a layer using

powerful painting and selection tools. The more

you work on combining multiple images, the

more you’ll ﬁnd yourself using masks.

Layer Mask
Essentials

The mask is the black-and-white area attached to the layer
thumbnail. It contains all the transparency information that
the layer needs to isolate the ﬂower from the background.

In this chapter, you’ll revisit

several techniques that you

learned in Chapter 5, “Selec-

tion Tools and Techniques.”

Masks generally start as a

selection, which is then at-

tached to a layer. The mask can

be reﬁned by adding to it with

black or subtracting with white.

Learning to create and modify

masks is an important skill that

becomes signiﬁcantly easier

with a little practice.

112 Chapter 7 Layer Masking

Adding Layer Masks
The best way to learn about Layer Masks is to
jump right in and create one. You’ll start with an
easy image, but one that will help illustrate the
important concepts. Let’s get started:
1. Open the ﬁle Ch07_Mask_Start.tif from the
Chapter 7 folder on the book’s CD.
2. Convert the Background layer into a ﬂoating
layer by double-clicking its name in the Lay-
ers panel. Name the layer Tower.
3. Select the Quick Selection tool from the Tools
panel.
4. Make a selection of the blue sky.
5. Reverse the selection by choosing Select >
Inverse. The building is now selected.
6. Click the Add layer mask button to add a
mask to the layer.
7. To make it easier to see the edges of the
border, place a solid color layer behind the
Sundial layer. Choose Layer > New Fill Layer
> Solid Color. Choose a color that is not in
the image, such as green.
8. Drag the ﬁll layer below the Sundial layer in
the Layers panel.
9. Depending on the accuracy of your initial
selection, your mask may be usable as is. If
needed, you can quickly touch it up using the
Brush tool.

Layer Mask Essentials 113

10. Click the Layer Mask thumbnail to select it.

11. Activate the Brush tool by pressing B or by

choosing it from the Tools panel.

12. Press D to load the default colors of black and

white. Black will add to a mask and create

transparency; white will subtract from the

mask. Using gray or blurring will create a

softer edge.

13. Zoom in to better see your edges. You can

use the Zoom tool or the Navigator panel to

get a better look at your edges.

14. Paint with a soft-edged brush to reﬁne the

mask. If you add too much to the mask, press

X to toggle the mask colors. Remember,

painting with black will add to the mask

(hence removing or masking the image).

15. You can improve the edges of the mask by

using the Blur tool or the Smudge tool on the

edges. You can stop tweaking when you are

satisﬁed with your results.

Disabling Layer Masks

The primary beneﬁt of masks is their ﬂexibility. In the previous

section you explored that ﬂexibility by adding and subtracting to

a mask. This ﬂexibility can also be used to temporarily disable a

mask. This can be useful if you want to check your progress or if

you need to restore the original image to use on another project:

1. Work with the Tower image from the previous exercise or open

the ﬁle Ch07_Mask_End.tif from the Chapter 7 folder.

2. Select the Layers panel so it is active.

3. Shift-click the Layer Mask thumbnail to disable it. Alternately,

you can right-click the mask’s thumbnail to access more op-
tions, such as deleting it and permanently applying it.

Shift-clicking a Layer Mask’s thumbnail
will temporarily disable the mask.

4. To re-enable the mask, Shift-click its thumbnail again.

114 Chapter 7 Layer Masking

Deleting Layer Masks
After going through the effort of creating a mask, you are unlikely
to want to permanently discard it. But if you change your mind
and are certain you want to delete it, doing so is easy:
1. Work with the Tower image from the previous exercise or open
the ﬁle Ch07_Mask_End.tif from the Chapter 7 folder.
2. Select the Layers panel so it is active.
3. Click the Layer Mask thumbnail. Drag it to the trash icon in
the Layers panel.
4. A dialog window appears asking you to decide what to do with
the mask:

•

•

•

Delete: Discards the mask and restores the image to its
premasked state.
Cancel: Allows you to cancel the command and return the
image to its masked state.
Apply: Permanently applies the mask and deletes the pix-
els that were originally masked.

5. Click Apply to permanently apply the mask. The mask is
used to permanently discard portions of the masked layer in a
destructive edit.

Using Vector Masks

24

VIDEO
TRAINING
Layer Masking

Most users choose to work with the raster-based Layer Masks
previously discussed. These raster-based masks tend to be the easi-
est to work with and allow the most ﬂexibility in editing due to the
wide variety of tools you can use to modify the mask. However,
some users prefer to work with vector tools like the Pen tool or the
Shape tools because of personal preference (or more experience
with programs like Adobe Illustrator). There are several ways to
add a Vector Mask:
•
-87After you’ve added a raster Layer Mask, click the Add layer
mask button in the Layers panel to add a second mask that is
vector-based.
•
-87To add a Vector Mask initially, Command/Ctrl-click the Add
layer mask button when adding the ﬁrst mask.

Mask Creation Strategies 115

•

To add a new (empty) Vector Mask, you can choose Layer >
Vector Mask > Reveal All.

•

To hide an entire layer, choose Layer > Vector Mask > Hide All.

Mask Creation Strategies

There are many different approaches to creating Layer Masks.

The approach you should take will vary based on your source im-

age. Let’s try four different images and techniques to perfect your

Layer Masking ability.

Using a Gradient as a Mask

When designing, you may need to gradually blend the edges of

an image. This can be easily accomplished by combining a Layer

Mask and a gradient. Let’s give it a try:

1. Open the ﬁle Ch07_Gradient_Mask.tif from

the Chapter 7 folder.

2. Duplicate the Background layer by pressing

Command/Ctrl+J.

3. Select the top layer and choose Image > Ad-

justments > Desaturate.

4. With the topmost layer active, click the Add

layer mask button at the bottom of the Layers

panel. A new, empty Layer Mask is added to

the layer.

5. Press G to select the Gradient tool.

6. Press D to load the default colors of black

and white.

7. From the Options bar, choose the black-to-

white gradient. If it’s not available, choose

Reset Gradients from the Gradient Picker’s

submenu.

116 Chapter 7 Layer Masking

The gradient mask allows the image to blend between the
grayscale and color image.

8. With the Layer Mask selected, click and drag to create a new lin-
ear gradient going from top to bottom in the document window.
The new Layer Mask will create a gradual blend from the
grayscale version to the colored version.

25

VIDEO
TRAINING
Alpha Channels

This technique of adding a mask can also be used on one layer
to create a gradual fade to transparency or to a different layer
stacked beneath.

Using a Channel
Oftentimes, a channel will get you very close to a perfect Layer
Mask. This technique works particularly well when the subject
is against a high-contrast background (such as a sky or a wall),
and it works very well with ﬁne details like hair. The image can
be masked so it is ready for integration into a composite image.
For example, a masked image could be used to add a palm tree to
another photo. Let’s give it a try:
1. Open the ﬁle Ch07_Channel_Mask.jpg from
the Chapter 7 folder. This image was shot
against a night sky using a ﬂash.
2. Switch to the Channels panel and examine
the red, green, and blue channels. Look for
one with high contrast from the background.
While all three channels are fairly high con-
trast, the green channel stands out the most.

Mask Creation Strategies 117

3. Duplicate the green channel

by dragging it onto the New

Channel icon at the bottom

of the Channels panel (it

looks like a pad of paper).

4. Rename the new channel

Selection by double-clicking

its name.

5. With the Selection channel

selected, press Command/

Ctrl+L to invoke a Levels

adjustment. Levels is a pow-

erful command that allows

you to adjust the gamma

(gray) point as well as the

black and white points.

6. Move the black slider to the right, setting the Input Level to

around 60. The black in the channel should get crisper.

7. Move the white slider to the left, setting the Input Level to

around 100. The gray areas in the channel should switch to

pure white.

8. Move the middle (gray) slider to reﬁne any gray spots in the

channel. A value of 2.25 should be approximately correct.

9. Command/Ctrl-click on the Selection channel’s thumbnail to

load the selection.

10. Turn off the visibility for the

RGB channels by clicking

the RGB composite chan-

nel’s visibility icon. Turn off

visibility for the Selection

channel.

11. Switch to the Layers panel.

12. Turn the Background layer

into a ﬂoating layer by double-clicking its name in the Layers

panel. Name the layer Palm Tree.

13. Click the Add layer mask button at the bottom of the Layers

panel.

118 Chapter 7 Layer Masking

Using the Color Range Command
Sometimes, a color (or range of colors) will be
very present in your image. This color can be
used to quickly create an accurate Layer Mask.
Even if the color cannot be used to select the
object entirely, you can always harness the Brush
tool to clean up stray areas.
1. Open the ﬁle Ch07_Color_Range.jpg from
the Chapter 7 folder.
2. Turn the Background layer into a ﬂoating
layer by double-clicking its name in the Lay-
ers panel. Name the layer Bees and Flower.
3. Choose Select > Color Range to make a selection based on a
range of colors. Select the Localized Color Clusters option to
reduce the selection area to just the chosen colors.
4. With the Eyedropper tool, click within the yellow area of the
ﬂower to make an initial selection. Hold down the Shift key and
drag through other areas of the ﬂower to add to the selection.
5. Leave the Fuzziness set to a low value
(30–40). When most of the ﬂower is selected,
click OK to create an active selection.
6. Click the Add layer mask button for the layer.
The petals will display well, but parts of the
ﬂower will be missing.
7. Add a solid color layer to make it easier to see
your edges. Choose Layer > New Fill Layer
> Solid Color. A purple layer will help things
stand out nicely. Click OK and drag the solid
layer below the masked ﬂower.
8. Examine the masked layer closely. You will
need to paint in part of the center of the ﬂow-
er. Additionally, some of the petals contain
unwanted transparency. You may also see
some leaves or stems that have bled through.
You can ﬁx all these problems quickly using
the Brush tool.

Mask Creation Strategies 119

9. Press D to load the default colors of black

and white.

10. Select the Layer Mask attached to the Bees

and Flower layer.

11. Press B to activate the Brush tool. Adjust the

size of the brush and its hardness settings so

you have a small brush with a gentle edge

(an 80-pixel brush with a hardness of 75% is

a good place to start). Make sure the brush is

set to 100% opacity.

12. Paint in spotted or missing areas with white.

You can remove any unwanted areas by painting with black.

13. When ﬁnished, you can save the image as a layered ﬁle such as

a TIFF or PSD formatted ﬁle.

Using Calculations

You explored the Calculations command to create an advanced

selection in Chapter 5. This command uses channel data to create

a new alpha channel. You can then reﬁne the channel to create an

accurate selection. You can also take this one step further to make

a high-quality layer mask. Let’s give it a try:

1. Open the ﬁle Ch07_Calculations.tif from the

Chapter 7 folder.

2. Turn the Background layer into a ﬂoating

layer by double-clicking its name in the Lay-

ers panel. Name the layer Castle.

3. Call up the Channels panel and closely

examine the channels for a high contrast

between the lamp and the background.

While all three channels have contrast

between the sky and the castle, the blue

channel has the best.

4. Invoke the Calculations command by choos-

ing Image > Calculations.

120 Chapter 7 Layer Masking

5. Set Source 1 to the Blue channel; set Source
2 to the Red channel and select the Invert
check box. The red channel differs most from
the blue channel in this image, so it will cre-
ate a good matte.
6. Experiment with different blending modes
so you get a clearer separation between the
castle and the sky. In this case, the Vivid
Light mode works best to create a new chan-
nel. Click OK.
7. The new channel will need a little touch-up.
You can get the channel near perfect with a
Levels adjustment. Press Command/Ctrl+L
to invoke the Levels dialog box.
8. Adjust the black, white, and gray points
for Input Levels to improve the matte. The
results will be closer but not complete. Click
OK when satisﬁed.
9. With your Brush tool, paint out the windows
with black.
10. You then need to reverse
the channel so the area you
want to discard is black.
Press Command/Ctrl+I to
invert the channel.
11. Soften the selection by
blurring it. Choose Filter >
Blur > Gaussian Blur; set
it to a value of 1 pixel and
click OK.
12. Load the channel as a selection by Com-
mand/Ctrl-clicking the channel’s thumbnail.
13. Turn on the visibility icon for the RGB chan-
nels and turn it off for the alpha channel.
14. Switch to the Layers panel and select the
Castle layer.
15. Click the Add layer mask button to apply a
mask to the selected layer.

Reﬁning Masks 121

Reﬁning Masks

TIP

By now you should be feeling more comfortable making layer
masks. However, there’s always room for improvement (at least
where masks are concerned). Let’s take a look at three ways to
reﬁne or adjust a mask.

The Masks panel offers several
other useful commands. You can
load a mask as a selection, apply a
mask, disable its visibility, or discard
it. Additionally, you can use the

Color Range or Invert commands

Using the Masks Panel

to further reﬁne the selection. The
Masks panel consolidates all the

Photoshop CS4 offers the new Masks panel just for reﬁning masks.

masking commands into a single

It combines several tools and commands into one location, and

location, which can save you valu-

makes it much easier than before to adjust a mask (even after

able time.

applying it). In fact, the Mask Edge and Color Range options are

identical to the selection commands you’ve previously explored.

1. Open the ﬁle Ch07_Masks_Panel.psd from

the Chapter 7 folder.

2. Select the Fire Hydrant layer’s mask.

3. Experiment with the Density and Feather

sliders to see their effects.

•

Density: Reduces the overall impact of
the mask by essentially lowering the opac-

ity of the layer mask.

•

Feather: Creates a gentle edge to the
mask.

4. Set Density to 100% and Feather to 0 px.

5. Click the Mask Edge button to open the Re-

ﬁne Mask dialog box. The controls are identi-

cal to the Reﬁne Edge dialog box except here

they are used to modify the layer mask.

122 Chapter 7 Layer Masking

6. Adjust the Mask Edge properties to remove
fringe from around the image.
7. Click OK to apply the change to the layer
mask.

Maximum and Minimum
Photoshop offers two specialty ﬁlters for reﬁning
masks. Lumped into the amorphous “Other” cat-
egory, most users miss the Minimum and Maxi-
mum ﬁlters. Both are useful for modifying a mask
because they can expand or contract the mask.

•

•

Maximum: The Maximum ﬁlter applies a choke, which
spreads the white areas and chokes the black areas. This ﬁlter
will expand a Layer Mask outward, which is useful if the matte
is hiding too much of the image.
Minimum: The Minimum ﬁlter applies a spread, which
expands the black areas and shrinks the white areas. This ﬁlter

will reduce a Layer Mask and contract it. This is useful if the
matte has a fringe around the outside edge.

The Minimum ﬁlter modiﬁed the Layer Mask by contracting it. The minor adjust-
ment removed the dark edge.

1. Open the ﬁle Ch07_Flower.psd from the Chapter 7 folder.
Notice the thin black border around the ﬂower.
2. Select the Layer Mask’s thumbnail.

Reﬁning Masks 123

3. Choose Filter > Other > Minimum to contract the mask.

A value of 3–7 pixels should be enough to contract the edge

to remove the border.

4. Click OK when satisﬁed.

Using Smudge and Blur

Sometimes, a mask is close to being ready to ap-

ply but needs a little touch-up. What better way

to do this than to paint? By using the Blur and

Smudge tools you can polish problem edges.

•

Blur: Choose the Blur tool to soften a hard
edge that looks unnatural. Just be sure the

mask is selected before blurring.

•

Smudge (Lighten): Choose the Smudge tool
and set its mode to Lighten in the Options

bar. This is useful for gently expanding the

matte. Leave the Strength set to a low value

to make gentle changes.

•

Smudge (Darken): Choose the Smudge tool and set its mode
to Darken in the Options bar. This is useful for gently contract-

ing the matte. Leave the Strength set to a low value to make

gentle changes.

Open the ﬁle Ch07_Lion_Mask.tif to experiment with the Smudge

and Blur tools.

Adjusting Content Within a Mask

By default, layer masks are linked to their respec-

tive layers. Applying a transformation (such as a

Free Transform command) will affect a layer and

its layer mask. However, there are times when

you won’t want this default behavior to occur.

Sometimes, it is useful to adjust the contents of

a masked layer without repositioning the mask.

Let’s give it a try:

1. Open the ﬁle Ch07_Mask_Content.psd from

the Chapter 7 folder. Even though the layer

mask is accurate, too much of the layer’s

content is obscured.

124 Chapter 7 Layer Masking

2. Click the chain icon between the layer
thumbnail and layer mask icons for the News-
paper layer. You can now manipulate the
layer content or its mask independently.
3. Select the Newspaper layer’s thumbnail to
modify the visible pixels of the layer.
4. Press Command/Ctrl+T to invoke the Free
Transform command. Scale the Newspaper
layer smaller and move it slightly to better ﬁt
the opening in the newspaper stand. Click the
Commit button to apply the transformation.

Advice on Masks
Layer masking and advanced selections go hand in hand. The
more you practice one, the easier both will get. New users often
lapse into bad habits and are drawn back to features like the Eras-
er tools or the Extract command. While these may seem easier, in
the long run they are not. Learn to work like a professional, and
you’ll achieve professional results.

Compositing
with Layers

When Photoshop debuted,

8

it did not have layers. In fact,

its original purpose was to touch

up frames of motion picture and

photography ﬁlm. It was, as its

name implied, a photo shop that

provided a digital darkroom

where photos could be enhanced,

color corrected, and even

repaired. Over time, however,

people wanted to do more with

Photoshop, such as create print advertisements and television

broadcast graphics. As people expected Photoshop to do

more, Adobe responded with the introduction of layers.

What Are Layers?

In traditional cel animation, artists would

paint their animations onto clear sheets of

acetate. These clear sheets would often

contain a single character or element.

They could then be laid together with sheets

containing other characters and backgrounds to

create a composited scene.

Layers work the same way. Each layer can contain

discrete elements of your design. You then combine

them to create the ﬁnished product. Layers can contain

photos, text, logos, shapes, and even textures. There are

lots of ways to create and manage layers, but it all comes

back to having an organized design. Every layer should

have a clear, descriptive name to make your design workﬂow easier.