For efficiency’s sake we will bypass two
customary procedures. First, a few para-
graphs ago, I did something that I find
exceedingly irritating when other authors try
it. I asserted that a certain way of doing things
is better than the customary alternative, and
expected you to take it on faith. Yet, if I
had stopped to prove that straight
LAB
correction indeed yields better results than
RGB
in canyon images, there would have
been an eight-page detour.
So, in the interest of speed, the first half of
each chapter concentrates on the how, not
the why. I will say things that might be
labeled matters of opinion without stopping
to prove they are so. Take my word for them if
you like; if you’d rather not, they are backed
up in the “Closer Look” section.
Also, the first halves don’t assume much
Photoshop expertise. I try to give simple
explanations of each command being used.
The second parts play by no such rules, and
often dive right into techniques familiar only
to a sophisticated audience. And they don’t
offer many explanations of Photoshop basics.
LAB
is always an intermediate step. Files
must be converted into it before the fun
begins and out of it afterward. Almost every-
one will be converting into
LAB
from an
RGB
file. When finished, some will convert
back to
RGB
and others, needing a print file,
will go to
CMYK
. For the time being, it doesn’t
matter which; we will assume for conve-
nience that it goes back to
RGB
.Your defini-
tions of
RGB
and
CMYK
in Photoshop’s Color
Settings dialog don’t matter yet, either. We’re
now ready to tackle some canyons.
A 30-Second Definition of
LAB
It would take a wheelbarrow to carry every
way of defining color that’s been propounded
in the last century. Our current
LAB
is one of
the most prominent, an academic construct
designed not just to encompass all conceiv-
able colors (and some that are imaginary, a
fascinating concept that we’ll explore at
length later, notably in Chapter 8), but to sort
them out in a way that relates to how humans
see them.
The version of
LAB
used in Photoshop was
born in 1976, child of a standards-setting
group called the International Commission
on Lighting and known by its French ini-
tials,
CIE
.
There have been several close relatives.
We need know nothing about them, but color
scientists feel that we should use a more
precise name for our version. They call it
CIELAB
or L*a*b*, both of which are a pain to
pronounce and maddening typographically.
Photoshop calls it “Lab color,” but the name
has nothing to do with a laboratory: the
L
stands for luminosity or lightness; the
A
and
The Canyon Conundrum 5
Figure 1.3 A more vivid version of Figure 1.2, prepared
using the
LAB
recipe of this chapter.
