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A
B
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1
The Canyon Conundrum
LABhas a reputation for enormous power, yet virtually all reference
materials that advocate its use illustrate its capabilities with a single
class of image. This chapter introduces the basic LABcorrection method
and explains why it is so extraordinarily effective—if you happen to
have a picture of a canyon.
eep in Death Valley, land of desolation and summertime heat
in the high 120s, a narrow canyon holds several lessons
about color, photography, human perception, and a power-
ful digital imaging tool.
Parts of the clayish soil contain mineral deposits that
create striking color variations, especially when the light
hits just right in the late afternoon. The effect allegedly reminds some
people of a painter mixing up the tools of his trade.
So, it’s called “Artist’s Palette,” a considerable stretch. These dull tints
have about as much to do with those found on the palettes of Renoir or
Rembrandt as this book does with animal husbandry. But nothing seems
great or small except by comparison. It’s such a shock to encounter green
or magenta dirt that it seems absolutely blazing next to the monotony
of the surroundings. People stand and stare at Artist’s Palette for hours,
seeing subtleties that cameras can’t record and imagining brilliant colors
that cameras don’t think are there.
We can leave aside the philosophical question of whether the reality is
these dull colors that the camera saw in Figure 1.1A, or the comparatively
bright ones conjured up by the infinitely creativehuman visual system.
The fact is, if this picture is a promotional shot or even something for a
nature publication, the original isn’t going to fly. Anybody would prefer
Figure 1.1B, which was created in approximately 30 seconds in LAB.
When I first wrote about LAB,ina 1996 column, I used a canyon shot
Figure 1.1This Death Valley canyon is noted for its strangely colored clay. Green soil like that on
the right side of this photograph is so unusual that people remember it as being greener than what
the camera saw. Canyon images are often used to illustrate the power of LABcorrection (bottom).
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4 Chapter 1
from Capitol Reef National Park in Utah. My 4, treating it in a slightly more complex way)
book Professional Photoshopgoes around 100 but it’s much better than any comparable
miles to the south with a shot from Canyon- moves in RGBor CMYK, and even ifyou could
lands National Park. match the quality in some other colorspace it
Another Photoshop book illustrates its LAB would take far longer.
section with a shot from Bryce Canyon Na- When Iwheeled out that first canyon shot
tional Park. A third uses a scene from Grand in 1996, I likened LABto a wild animal: very
Canyon National Park, and a fourth a canyon powerful, very dangerous. That label has
from the Canadian Rockies. And author Lee stuck. Use of LABis now widespread among
Varis has a scintillatingLABexercise, repro- top retouchers, but a huge fear factor limits
duced here in Chapter 16, that brings out the the techniques they use it for. Most of those
best in a canyon in North Coyote Buttes, on who claim to be LAB users are only doing
the Arizona/Utah border. what’s described in the first five chapters
Start to detect a pattern? here, missing out on much magic.
Yes, indeed. LAB does really, really well You can’t blame them for being satisfied
with canyons. And you don’t even need to with what they’ve got, because those limited
know how it works to make the magic hap- LABtools can make an extraordinary differ-
pen; the approach to canyons is simplicity ence in image quality. They are also so simple
itself. Figure 1.1B isn’t the bestwe can do in that beginners can enjoy their benefits.
LAB(we’ll be revisiting this image in Chapter I hope, and the publisher hopes harder,
that people with limited experience will
learn enough to dramatically improve their
pictures. On the other hand, some of what
follows either is unbearably complicated or
suggests methods that only power users can
fully appreciate. For the best of reasons, it
isn’t customary for Photoshop books to cater
to novices and simultaneously include mate-
rial that leaves experts cursing in frustration
until they re-read it for the eighth time.
Special handling is clearly required.
The Rules of the Game
Each of the first six chapters is divided into
two parts, readily identifiable by a change
in typeface. If you’re just trying to get into
working with LABas quickly as possible, you
can skip the second part of each chapter,
which is more analytical, and can be some-
what difficult to follow.
Figure 1.2Like Figure 1.1, this image features colors
that are possibly accurate, yet too subdued when taken
in the context of the scene. This canyon is called
“Yellowstone” for a reason. The yellowness of the
canyon walls should be played up.
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The Canyon Conundrum 5
For efficiency’s sake we will bypass two designed not just to encompass all conceiv-
customary procedures. First, a few para- able colors (and some that are imaginary, a
graphs ago, I did something that I find fascinating concept that we’ll explore at
exceedingly irritating when other authors try lengthlater,notably in Chapter 8), but to sort
it. I asserted that a certain way of doing things them out in a way that relates to how humans
is better than the customary alternative, and see them.
expected you to take it on faith. Yet, if I The version of LABused in Photoshop was
had stopped to prove that straight LAB born in 1976, child of a standards-setting
correction indeed yields better results than group called the International Commission
RGB in canyon images, there would have on Lighting and known by its French ini-
been an eight-page detour. tials,CIE.
So, in the interest of speed, the first half of There have been several close relatives.
each chapter concentrates on the how, not We need know nothing about them, but color
the why. I will say things that might be scientists feel that we should use a more
labeled matters of opinion without stopping precise name for our version. They call it
to prove they are so. Take my word for them if CIELABorL*a*b*, both of which are a pain to
you like; if you’d rather not, they are backed pronounce and maddening typographically.
up in the “Closer Look” section. Photoshop calls it “Lab color,” but the name
Also, the first halves don’t assume much has nothing to do with a laboratory: the L
Photoshop expertise. I try to give simple stands for luminosityor lightness; the Aand
explanations of each command being used.
The secondparts 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.
LABis 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 RGBand 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 RGBand CMYKin 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 LABis one of
the most prominent, an academic construct
Figure 1.3A more vivid version of Figure 1.2, prepared
using the LABrecipe of this chapter.
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6 Chapter 1
B stand for nothing. The name should be systems, such as Quantel’s Paintbox, nobody
pronounced as three separate letters, as we thought that people would be perverse
do with other colorspaces. enough to use LAB for such purposes in
We need not concern ourselves with LUV, Photoshop. Instead, it’s there as a means of
LCH,xyY,HSB,XYZ, or other color definitions expediting color conversions.
(at least until Chapter 13), because Photo- The language of color is notoriously im-
shop fully supports only three:CMYK,LAB, precise. If you work in RGB, 255R0G0Bdefines
and RGB. Pretty much everybody has to use pure red. Unfortunately, there’s no agreement
either CMYKor RGB; increasingly people are as to what pure redmeans. Anybody needing
being called uponto use both. to know exactly what kind of red you intend
All printing is based on CMYK, although would have to find out what your Photoshop
most desktop color printers either encourage Color Settings are, because there are different
or requireRGBinput. Web, multimedia, and definitions of RGB, each of which has its
other display applications require RGBfiles. own idea of what constitutes red. There is,
Commercial printers want CMYK. But LAB however, only one Photoshop LAB.
files are usually unwelcome, except in Photo- If you wish to order a car in a different
shop, Photo-Paint, and other specialized color than the model you test-drove, it won’t
applications. A few raster image processors be sufficient to say you want a red one. Before
(RIPs) for printing devices also claim to be accepting your money, the dealer will insist
able to handle LAB, but gambling that they that you look at a swatch book to make sure
actually do is a sport for the dedicated player you get the red you expect. You won’t hear
of Russian Roulette. anything about LAB,but the supplier of the
Although LABis a distant relative of HSB, vehicle’s paint will, if you complain that
which has been used as a retouching and the color doesn’t match and the car manu-
color correction space on many high-end facturer agrees with you. It wouldn’t do for
Figure 1.4Photoshop defaults (left) look slightly different than the curves in this book (right). In the gradient at
the bottom of the grid, note that the LABdefault has darkness at the left (in agreement with the Photoshop RGB
default), but this book uses lightness at the left, which is the default for CMYKand grayscale images. To reverse the
orientation, click inside the gradient bar below the grid. Also, the default uses gridlines at 25 percent increments,
whereas the book uses 10 percent intervals. To toggle between the settings, Option– or Alt–click inside the grid.
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The Canyon Conundrum 7
Figure 1.5Measuring the lightness range of
the interest object. After the file is in LAB, call
up the Curves dialog and, with the Lightness
curve open, click and hold the mouse over an
important part of the image. A circle appears
on the curve, indicating the value of the point
underneath the cursor. If you move the cursor
around the interest object with the mouse
button still depressed, the circle will move
with it. The tonal range of the canyon walls
falls between the two diagonal lines.
artwork that represents that
color, you’ll be getting the LAB
information as well, just as
Photoshop gets LABvalues from
Pantone, Inc., that enable it to
construct the PMS (Pantone
Matching System) colors that
are the de facto standard in the
graphics industry.
Assembling the Ingredients
We will start with, shockingly
enough, a canyon. You can fol-
low along with the image on the
enclosed CD, or you may use
one of your own, provided that
you think you understand why
canyons make such great LAB
the manufacturer and the paint supplier fodder. Regrettably, there’s more to life than
to scream and wave swatch books in each canyon shots. And just as LABdoes extremely
other’s faces. They specify LABvalues, plus a well on certain classes of image, it does
tolerance for how far off the paint can be. poorly on others. Much of this book is aimed
In the event of a dispute, they whip out a at showing how to distinguish such images.
spectrophotometer and measure its color. If you do choose to use your own image,
If the manufacturer
hires you to produce
Figure 1.6TheLABcurves
that produced Figure 1.3.
Note how the Lcurve has
been made steep in the area
indicated in Figure 1.5. The
AandBchannels have also
been steepened, by rotating
them around the unchanged
midpoint.
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8 Chapter 1
Figure 1.7 InLAB,unsharp masking
must be applied to the Lchannel only,
and should be evaluated with the screen
display at 100% view. The numbers shown
here can be used as defaults, but better
results can be had by customizing them
to the specific image.
Also, it appears to be just the
kind of image we’re looking for,
needing a color boost nearly as
badly as the Artist’s Palette of Fig-
ure 1.1 did. The canyon walls here
are slightly off-gray. Not nearly
enough, however, considering that
the most famous national park
in the world bears the name of
that particular color, for this is a
picture of the Grand Canyon of
the Yellowstone.
The following recipe for bring-
ing out the colors that are hidden
in such images will be refined
considerably in coming chapters.
But to get started on making
something more convincingly yel-
low, like Figure 1.3, make yourself
a copy (or a duplicate layer) of the
RGBoriginal if you think you’d like
to have something to compare
your work to afterwards.
Next, Image: Mode>Lab color.
three types should be avoided. First, the The picture should lookno different, but the
image should not contain colors that are identification bar at its top should now read
already brilliant or highly saturated. Second, Lab rather than RGB.
it shouldn’t have an overall color cast. If you Call up the Curves dialog with Image:
think that the Figure 1.1A is too gray or too Adjustments>Curves (keyboard shortcut:
blah or whatever, fine, but if you think it’s Command–M Macintosh; Ctrl–M PC). If
too blue, you won’t be able to fix it without you’ve never worked in LAB before, the
reading Chapter 4. And third, nobody should Photoshop default treatment of lightness-to-
have applied unsharp masking yet. the-right is probably still in effect. Although
Figure 1.2 seems to qualify.It hasn’t been there’s no technical advantage either way, this
sharpened; there’s nothing even close to a bookuseslightness-to-the-left, so you should
bright color in the canyon, and the clouds probably change over now by clicking inside
appear to be white, not some goofy hue that the gradient bar at the bottom of the curve, as
would indicate a cast. shown in Figure 1.4.
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The Canyon Conundrum 9
Also, the default curve box has gridlines • Before clicking OK, switch to the Light-
at 25 percent increments, a little coarse for ness curve. Move the cursor back into the
serious work. Option–click (Mac; Alt–click picture over part of the canyon, and click and
PC)inside the box, and the grid changes to hold. While the mouse button is depressed, a
10 percent increments. circle appears on the curve, indicating where
Having made these cosmetic changes to the point under the cursor is located. Still
the interface, we proceed to the recipe. holding the mouse button down, move the
cursor to various parts of the canyon, and
A Canyon Correction, Step by Step
note the range where the circle is moving. In
• Click into the word Lightness above the Figure 1.5, I’ve inserted red lines to indicate
curve grid and change it to a. Move the top where on the curve mostof the pixels repre-
right point of the curve one gridline to the senting the canyon are located. That area of
left; that is, a tenth of the way toward the left the curve has tobe made steeper. Sometimes
axis. Move the bottom left point one gridline we do this by inserting points where my red
to the right. The two points must be moved lines are and lowering one while raising the
an equal amount, because the resulting curve other. Here, I simply raised the center of the
needs to pass over the same center point as it curve, as shown in Figure 1.6.
did originally. • Apply the curves by clicking OK in the
• Without clicking OK, switch over to b, dialog. Now, display the Lchannel only, either
and apply the same changes. In both chan- by highlighting it in the Channels palette or
nels, we’re making a steeper line by, in effect, by using the keyboard shortcut Command–1
rotating it counterclockwise around the (Mac; Ctrl–1 PC). Then, Filter: Sharpen>
center point. Unsharp Mask. If you are familiar with
These two moves are the ones unique to how the dialog in Figure1.7 works, you’ll have
LAB, the ones that drive colors apart from a good idea of what numbers to enter. If
one another in a way that other colorspaces not, enter Amount 200%, Radius 1.0 pixels,
can’t equal. What comes next could be done Threshold 10 levels, understanding that better
elsewhere. So, stop now, clickOK,and return results will be possible after you’ve read
to RGB if you must—but you should really Chapter 5. Hit OKand compare it to the orig-
leave the dialog open, and try to complete inal. If satisfied, return the image to RGB if
the magic in LAB. that’s what your workflow needs, or convert it
The following two steps can be modified to to CMYK, as I did for this book.
taste if you’re comfortable with curves and/or
Finding Color Where None Exists
sharpening settings.
If you’ve never worked on the A and B The first two steps established the color vari-
channels before, then you’ve never worked ation that gives LABits reputation for realism.
on anything like them before. On the other The third added snap, and the fourth sharp-
hand, if you know how to apply curves to a ness. If you are considering how this might
grayscale document, then you know how to have been done in RGBorCMYK, the bottom
apply themto the L. We’ll discuss the concept line is that Steps One and Two aren’t easy to
further in Chapter 3, but it boils down to this: duplicate. Step Three happens to be easier for
the steeper the curve, the more the contrast. LABin this particular image, but in other im-
Your task is to make the partof the Lcurve ages there’s no advantage. Step Four is some-
that encompasses the canyon steeper than times better done in LAB, although this time
the rest. it could be done equally well elsewhere.
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10 Chapter 1
But working in LABis fast, fast, fast. Once tier clime than Yellowstone. It’s Anza-Borrego
you get the hang of it, it should take about a Desert State Park, one of the hottest places in
minute to get this kind of result with a canyon the world. Located in Southern California
image. Let’s try another. just a short way from Mexico, it enjoys sum-
Figure 1.8 comes from a substantially nas- mer temperatures that rival Death Valley’s.
Rainfall is a pitiful inch or
A two each year.
Such conditions aren’t
exactly conducive to plant
life. The scraggly ocotillo
in the foreground at right
will wait patiently for five
years or so for enough win-
ter rain to permit it to blos-
som into orange and green
splendor. The rest of the
time, it sits and awaits de-
velopments, clothed in a
brown as drab as the back-
ground. This canyon was
cut not by a river, but by
repeated flash floods, be-
cause when the rain does
fall, the ground is too
parched to absorb it.
When you or I visit such
an area, we don’t find it
particularly colorful but we
B
certainly see more thanthe
monochromatic mess that
any camera would. When-
ever we look at a scene of
substantially the same
colors, our mind’s eye
breaks them apart, creat-
ing different levels of
brownness in the rocks
that artificial instruments
Figure 1.8The desert image at
top shows the lack of brilliant
colors and the shortness of range
that suggest an LABcorrection.
Bottom, after a literal repetition
of the steps that produced
Figure 1.3.
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