Margulis - Photoshop LAB Color.pdf - fotografia -ebook - ro3son

The Canyon Conundrum

LAB has 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 LAB correction 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 creative human 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 , in a 1996 column, I used a canyon shot

Figure 1.1 This 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 LAB correction (bottom).

Chapter 1

from Capitol Reef National Park in Utah. My

book Professional Photoshop goes around 100

miles to the south with a shot from Canyon-

lands National Park.

Another Photoshop book illustrates its LAB

section with a shot from Bryce Canyon Na-

tional Park. A third uses a scene from Grand

Canyon National Park, and a fourth a canyon

from the Canadian Rockies. And author Lee

Varis has a scintillating LAB exercise, repro-

duced here in Chapter 16, that brings out the

best in a canyon in North Coyote Buttes, on

the Arizona/Utah border.

Start to detect a pattern?

Ye s , in d e e d . LAB does really, really well

with canyons. And you don’t even need to

know how it works to make the magic hap-

pen; the approach to canyons is simplicity

itself. Figure 1.1B isn’t the best we can do in

LAB (we’ll be revisiting this image in Chapter

4, treating it in a slightly more complex way)

but it’s much better than any comparable

moves in RGB or CMYK , and even if you could

match the quality in some other colorspace it

would take far longer.

When I wheeled out that ﬁrst canyon shot

in 1996, I likened LAB to a wild animal: very

powerful, very dangerous. That label has

stuck. Use of LAB is now widespread among

top retouchers, but a huge fear factor limits

the techniques they use it for. Most of those

who claim to be LAB users are only doing

what’s described in the first five chapters

here, missing out on much magic.

You c a n’t bl a m e t h e m f or b e i n g s a t i s ﬁ e d

with what they’ve got, because those limited

LAB tools can make an extraordinary differ-

ence in image quality. They are also so simple

that beginners can enjoy their beneﬁts.

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 LAB as 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 1.2 Like 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.

The Canyon Conundrum

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.

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

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

Figure 1.3 A more vivid version of Figure 1.2, prepared

using the LAB recipe of this chapter.

Margulis - Photoshop LAB Color.pdf

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