38
INSTRUCTOR
NO
TES
Lesson 6: Masks
and Channels
Masks are a powerful way to control both where and how much an effect c
hang
es
an
image. This lesson guides students through the extensive Photoshop masking
features. Students start by creating a mask and refining it. Then they learn about
t
he
relationship between selections, masks, and c
hanne
l
s
.
This lesson builds on Lesson 3, Working with Selections, so make sure that you
r
students are
competent
in making selections before
introducing
Lesson 6.
If you have taught this lesson using previous editions of the Classroom in a Book,
you may notice that the design of the lesson files was updated for the 2022
r
e
le
as
e.
However, most of the lesson steps are the same, so you should not experience
m
uc
h
of a difference in teaching
it
.
Goals
for this lesson
Students should
understand
the differences between and the benefits of using
ma
sks
and channels. After completing this lesson, they should be comfortable using
ma
sks
to create selections, apply filters, and touch up
i
mages
.
Working with
masks
and channels
To a beginner, the differences among selections, Quick Mask mode, channels,
and
layer masks can be very confusing. You might explain it in terms of the
f
ollo
w
i
ng
key
d
i
ff
er
enc
es
:
Quick Mask mode is basically a selection marquee shown in a different
f
or
m.
Both are temporary, disappearing as soon as the current selection is c
hang
ed.
An alpha channel (a channel used for selection) is like a Quick Mask that can
b
e
Using
S
elec
t
and Mask
I
t
s
important
to be disciplined about using the
appropriate
tool, as described
i
n
t
he
sidebar Getting Better and Faster Results with Select and Mask. In Select
and
Mask, the simple Brush tool might be the most familiar and intuitive because
it
works similar to Quick
M
ask
:
You paint the mask. But there s a reason the
Br
u
s
h
tool is not at the top. The benefit of Select and Mask is in how the Quick
S
e
le
c
tion
tool can quickly find edges by recognizing content, and how the Refine Edge
Brush automates masking complicated edges like hair and fur. Therefore, in
S
e
le
c
t
and Mask,
it
s best to first use the Quick Selection and Refine Edge Brush
t
o
ols
to quickly create an accurate initial mask. If the Brush tool is used instead of
t
he
Refine Edge brush along edges such as hair outlines, the Edge Detection and Global
Refinements options (such as Smooth and Contrast) are much less effective.
In other words, if a student opens Select and Mask but they primarily use
t
he
40
INSTRUCTOR
NO
TES
At first, Select and Mask can seem daunting to use. It may help to place it in c
on
t
e
x
t
by discussing other methods of selecting complex edges such as using the Pen
or
Lasso tools, and when those other methods might be used instead of Select
and
Mask. Students may be unaware that traditional manual methods of masking
d
i
f
–
ficult edges such as hair involve advanced techniques that can use selections, c
han
–
nels,
Levels,
blur filters, and masks. Select and Mask combines that tedious
m
ultiple
step process into a single streamlined operation
t
ha
t
s easier to
u
s
e.
Because Select and Mask is designed to more quickly resolve difficult mask edges,
it
i
sn
t
always the best solution to a masking problem. For example, if the task is
t
o
separate an image of a
smartphone
or an airplane from its background, there are
no
Creating a
quick mask
Quick Mask mode is great for students because
it
s much more forgiving than
dra
w
–
ing a selection marquee. In Quick Mask mode, there is never any danger of acc
iden
–
tally dropping a carefully drawn se
le
c
tion.
If tools and commands
aren
t
working as expected, Quick Mask mode may still
b
e
on
since in that mode, tools affect only the selection mask and not the image itself. If
Using Puppet
Warp
There are two main ways to use Puppet Warp. You can rotate the content around a
point, as in this lesson, or pull a point to a different position to warp the c
on
t
en
t
.
ADOBE PHOTOSHOP CLASSROOM IN A BOOK (2022 RELEASE)
41
Creating a
pattern
for the
back
g
r
ound
You may want to point out to students that the handles for controlling
r
ounded
corners, and the
corresponding
options in the Properties panel, are available
f
or
Supplementing this lesson
You may want to reinforce the relationship between selections, channels, and
ma
sks
.
For example, reviewing how a selection can be converted into a mask or a c
hanne
l,
or how a channel can be loaded as a selection and made into a mask. You can als
o
compare QuickMask mode to layer
ma
sks
.
Students may want to try applying the Remove Background button in the
Properties
panel to the Model layer in the 06Start.psd lesson
file.
Remove Background is
b
a
si
–
cally a shortcut for applying the Select > Subject command, and then c
on
ver
ti
ng
Questions
The following questions are not in the
studen
t
s Classroom in a Book.
1 How does painting with black, white, and gray in a channel affect an image?
2 How do you apply a saved mask to an image or layer?
3 What is the
recommended
order for using the tools in Select and
M
as
k?
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INSTRUCTOR
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TES
Answers
1 Black areas completely protect an image from changes. White areas
ar
e
completely subject to change. In gray areas, lighter areas are more subject
t
o