behind the scenes spotlight on color theory and brightness 0

7/28/2019 Behind the Scenes Spotlight on Color Theory and Brightness 0

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B E H I N D the S C E N E SA T E C H N I C A L D I S C U S S I O N F R O M P O T L A T C H


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Full Spectrum

The CIE (Commission

International de I'Eclairage)

chromaticity diagram

of color space provides

a universal reference forall the colors of light visible

to the human eye.

Matched Color

Spectrum

Commonly used color-matching systems tend

to be shifted into the

green range while omitti

the very pure portions

of the visible spectrum.

CMYK Spectrum

The range of the standard

four process colors, or

CMYK, is also restricted

when it comes to pure

reds and greens and

comes up particularly

short in the violets.

RGB Spectrum

RGB computer monitors

pick out some of the

red and violet ranges

omitted by CMYK but f

well short of the spectr

included in matchedcolor systems.

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U N D E R S TA N D I N G C O L O R T H E O R Y

In the printing process, color begins with

a t ransparency o r i l lu s t ra t ion and ends

as a p r in ted image. Depend ing on your

l igh t source, mon i to r, p roof ing system

and paper cho ice , th is sam e image can

look d ramat ical ly d i fferen t . That ' s why

i t ' s so importan t to unders tand co lo rtheory and how it applies to the various

par ts o f the rep rodu ct ion p roce ss . I t ' s

a lso cr i t ical to know the mechan ics o f

whi ten ess and b r igh tness and the ro les

they each play in tran sla ting an imag e

to the printed page.

A D D I T I V E A N D S U B T R A C T I V E

C O L O R T H E O RY

Every photograph, every catalog, every

image broadcast to your television isr ep ro d u ced th ro u g h o n e o f tw o m ea n s .

The first is called additive color forma

t ion ; it relies on the mixing of light and is

used in p rep ress operat ions . The second

method is sub tract ive co lo r fo rmat ion ;

it relies on the absorption of light by

co lo ran ts and dominates the p r in t ing

p ro cess .

Additive Color

The next time the sun shines while it

rains, you ' ll find an example of a dditiveco lo r fo rm a t io n . T h a t ' s b ecau se a

rainbow con tains the th ree l igh t- rad iat ing

pr imary c o l o r s r e d , g reen and b lue,

or RGB. By mixing any two primaries, the

secondary colors of l ight result . Where

b lue and g reen over lap , cyan is p roduced ;

red and b lue p roduce magen ta; and red

and green give us yellow. When all these

co lo rs over lap , we perceive whi te .

Computer moni to rs create images using

add i t ive co lo r fo rmat ion , speci f ical ly

th rough the op t ical b lend ing o f g lowing

do ts o f red , g reen and b lue phosphor.

Subtractive Color

Four-color process printing depends on

sub tract ive co lo r. Accord ing to sub tract ive

co lo r theory, p igmented su rfaces

and mater ia ls absorb cer ta in wave

leng ths o f the l igh t that i l luminates them

and thereby ref lect o ther par ts . When

com bined , the l igh t waveleng ths th at

are absorbed and ref lected create a

spectrum of color.

The sub tract ive p r imary co lo rs are cyan ,

magen ta and yellowin prin t ing jargon ,

CMYK , with K for black. Cyan pigm ent

absorbs red and reflects blue and green

l igh t , magen ta absorbs g reen and

reflects red and blue, and yellow absorbs

b lue and ref lects red and g reen . B lackab so rb s a l l co lo r s .

Al though , nei ther system is inheren t ly

superior, the incompatibility of additive

and sub tract ive co lo r systems may affect

your perception of color quality. Because

RGB moni to rs p roduce co lo r by e lect ron i

cal ly "exci t ing" phosphor do ts un t i l they

em it l ight, the overall color quality will

tend to be sharper and more v iv id than

CMYK color. On the other hand, paper

su rface character is t ics have a d ramat ic

impact on CMYK color quality.

C O L O R S B Y D E S I G N

The Rolling Stones had it right when

san g , "You can ' t always get what you

want." Much as we'd like to believe

the full-color spectrum is our stage,

t h an 7 5 % o f t h e v i s ib l e sp ec t ru m , a

def ined by the " c h r o m a t i c i t y " d iag ra

(shown at r igh t) developed by the

Commission In ternat ional de Eclai ra

(CIE), is beyond the reach of CMYK

In printing, in computer design, even

match ed co lo r system s, you jus t can

reproduce the co lo rs that your miracu

lous little ol' eye can spy.

Here's why. Computer monitors, l ike

v is ion screens , depend on RGB add i t

co lo rs , wh ich come together as l i t t le

to form images. Printing, however, usub tract ive co lo r system cal led , as y

know, CMYKthe four-color standar

p rocess that uses cyan , magen ta , yel

and b lack inks .

Both m etho ds do a pretty good job o

rendering real l ife. But, let 's be truth

No system can reproduce the vivid c

that we can see in e laborate costum

and set designs .

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H E R E yo u A R E

R E A D Y to D E L I V E R

^ P E R F O R M A N C E0/ Y O U R L I F E .

The l igh ts are up and t ra ined on you so the aud ience can take in your

every gesture, each exquisi te detai l of your costume, and al l the r ich

colors an d te xtu res of the set. You are ready to sh ine.

But what wou ld h ap pe n if you were c loaked in darkn ess ins tead? Your

perfo rmance would lack v isual pop , be d ra ined o f energy and resu l t inless effec t ive communicat ion . Your aud ience would sh rug thei r shou l

ders an d, m or e th an l ikely, seek a refu nd on the ir t ickets . In a wo rd, you r

play would f lop.

In m an y ways, th ea ter is ju st l ike pap er. P ut simply, p ap er allows you

and the des igner to perfo rm. Whether you choose a sheet tha t ' s whi te

and b r i l l ian t ly b r igh t fo r a show-stopp ing perfo rmance, o r a lack lus tersheet , can m ak e all th e d ifference. An d th ere is qu ite a d ifference.


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In t roducing Shade and Br igh tness , par t o f Beh ind the Scenes by

Potlatch. What follows is a useful guide to paper optics. It covers every

thing from whiteness and brightness to the basics of color theory, ways

to me asu re co lor an d h ow ink works. You ' l l learn w hat mak es a wh ite

sheet whi te , wh at mak es it b r igh t , an d h ow t ran spa ren t inks ma ke co lo rs

dazzle on the page.

Why does i t matter? Simple. Because i t ' s your business to be an expert

o n all m att ers involving pa pe r. B ecause it 's your jo b to make sure that ink

perform s at its very best, w he th er in de sign or on press . Bec ause it 's yo ur

knowledgeab le serv ice tha t a t t rac ts cus tomers to your p r in t ing p lan t .

And because the quali t ies of paper p lay a huge role inmakeready a n d

t ime to co lo r, and that means money.

N O Wit S T I M E

to R A IS E T H E C U R TA I N . ..


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B E T T E R M A K E it B R I G H T

T A R G E T I N G B R I G H T N E S S

Simply put, wha t makes a bright sheet

bright is the amount of light i t reflects at

a waveleng th set by indust ry s tandards:

4 5 7 n an o m ete r s .

What 's that mean? Let 's back up for aquick review of color physics: A nanometer

is a unit of wavelength of electromagnetic

radiation. Visible light waves are catego

rized by length , and a wave's length

determines the co lo rs we see . Vio let

w av e len g th s , a t ab o u t 4 0 0 n an o m ete r s ,

are the shortest and red wavelengths, at

abou t 700 n anom eters , are the longest

waves of the visible light spectrum. At

457 nanometers , ou r b r igh tness measure

ment fa l ls wi th in the b lue waveleng ths .

Th is exp lains why we perceive b luersheets to be, in fact, brighter.

In the p re mium c oated paper indust ry,

brightness levels typically range from

88 to 98 , wi th 100 percen t rep resen t ing

the u l t imate in b r igh tness .

For your reference, Potlatch McCoy, the

sheet you 're holding, has a 96 brightness

rat ing . I t' s the b r igh tes t do m es t ic co ate d

sh ee t a vai lab le . Vin tage Gloss has a

9 1 b r ig h tn ess r a t i n g .

American Forest and Paper Association(AFPA) Quality Levels

Premium

No. 1

No. 2

No. 3

No. 4

No. 5

G.E. Scale 88 and above

85.0 th ru 87.9

83.0 thru 84.9

79.0 thru 82.9

73.0 thru 78.9

72.9 and below

Brightness Measurementsof Imported Papers

Imported Papers

Premium 110 lb. - Japan

Premium 110 lb . -U.K.

Premium 100 lb. - Germany

Gloss 80 lb .-U.K.

Dull 80 lb. - U.K.

ISO Sca le*

99

96-98

94

92-94

87-88

G.E. Scale

87.0

91.9

90.5

87.0

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G . E . V S I S O : A B R I G H T D I V I D E

Brigh tness i s measured two ways:

directional (also known as G.E.) and

nondirectional (ISO). Directional rating is

the s tandard used in the Uni ted S tate s .

Nondirectional rating is popular in Europe

and Asia . The b r igh tness ra t ings that

resu l t are o f ten d i ff icu l t to reconci le ,

so i t ' s importan t to remember that paper

qual i ty i s more than jus t a number.

Other facto rs , includ ing smoothness and

opacity, also play important roles.

Directional Ratings

A shee t i s i l lumina ted wi th a tung sten

bu lb d i rected a t i t f rom a speci f ied

anglein this case, 45 degrees. The light

that ref lects o ff the sheet i s then meas

ured by a photo receptor placed opp ositeit . Th is measurement i s u sed to con tro l

the b r igh ten ing agen ts added to pu lp

dur ing the paper-mak ing p ro cess .

Direct ional Rat ing Method

Nondirectional Ratings

Measurements are made f rom al l the

ambient light that is reflected. As a

result , nondirectional ratings often

register higher brightness even though,

by d i rectional measur em ents , the s heet

is really no brighter.

W H I T E + B R I G H T = D A Z Z L I N G C O L

Whiteness and b r igh tness real ly come

together when ink hits the sheet. It is

then that the degree o f wh i teness wi l l

either limit or amplify your sheet 's quali

and spectral range. And brightness, l ike a

d imm er s wi tch , wi l l e i ther go on lack lus

and low or come on strong and bold .

What does all this mean for the printed

page? From a color reproduction stand

point, the more lightboth whi te and

brightreflected from the paper, the

better. Why? Because a brighter, whiter

sheet improves contrast range for full

color, halftone and line reproduction.

I I N K , T H E R E F O R E I A M

Of course , th is en t i re d iscussion come s

down to one question How do shade

and b r igh tness affect ink perfo rmance?

The answer is, a lot.

True-to-life color reproduction requires

high-quality coated paper that equally an

vibrantly reflects all wavelengths of the

v is ib le l igh t spect rum. Whiteness and

brightnessand their ability to reflect

lightnot only amplify characteristics o

the ink, but they impact the appearanceand perform ance of the end product.

And that 's what it 's all abou t: Producin

a spectacu lar p r in ted p iece that your

cl ien t , and your c l ien t ' s c l ien t , wi l l

app laud . Which is why Po t la tch makes

the b roadest l ine o f qual i ty coated

paper avai lab le anywhere. Excep t ional ly

br igh t and in a range o f shades and

f in i sh es . D e l iv e r in g u n su rp assed

performanceevery t i m e .

Nondirect ional Rat ing Method

When reviewing brightness c la ims, make sure thenumbers are G.E, Brightness. * IS0 geometry wi th highU.V. light source.


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U T T I N G I N K on PA P E R

ause the inks on paper are transparpaper acts as a backlight reflectorfilter that reflects light through theFor accurate rendition of color, properortions of the three primary colorsghtred, green and bluemust exist

he light illuminating the inkf i lm.calls for a bright, white sheet.

THERE BE LIGHT

t makes a white sheet white? It alles down to light.

te light contains all colors. So whates a sheet white is, in effect, itsty to reflect equal amounts of red,n and blue lightthe entire visualtrum. It's really less a matter ofg "white" than of containing all color.

uly white sheet reflects the en tireal spectrum in equal amounts. Thee white, the higher degree of colorectance and the greater possibletral range. The lower the whitene ss,

less complete the spectrum ofected light, which can result indull,luster color.

A D E S O F W H I T Ewe in the printing industry are an

ommodating lot, welcoming paperdes that run the gamut underumbrella we call "white." In truth,mer sheets contain, and henceect, greater amounts of yellowsreds. Neutral sheets absorb allrs or wavelengths in equal amounts.the blue-white sheets so popular

e days really sing the blues.

these bluer shades less white?hnically speaking, yes. But to ourdern eyes, we've grown to registere-white sheets as white andht, while warm whites seemost creamy.

M E A SU RI N G PA PE R SH A D E

Whitenessin all its colorfulgloryismeasu red in a variety of ways. CIE, aninternational organization that sets standards for color measurements, designeda formula commonly referred to as CIEL,a,b. Another popular tool is known asthe 1947 Hunter L,a,b, developed byDr. Richard Hunter.

Put simply, these two formulas attemptto measure the dimensions of color bydefining its primaries. On a three-dimensional scale, L indicates luminosity, orthe degree of lightness from black(zero) to perfect white (100); a measuresredness when positive and greennesswhen negative; and b measures

yellowness when positive and bluenesswhen negative.

Here's a good way to remember thesescales: For L, think of a light bulb; highL

values mean the bulb is very bright and

Neutra l shade

Cool shade

therefore indicates high luminosity,while low L values dim the bulb or turnit off altogether. For a values, imaginetasting an apple: positive a valuesindicate redness, which is sweet andthus a positive experience, while negative

a values describe a bitter, unripe greenapple, surely a negative taste (unlessyou like the Granny Smith variety).For b, contemplate your moods:positive b values show off your positivelysunny, hence yellow, side; negativevalues give you the blues, a negativeexperience indeed.

Brightness is the measure of lightvolume at a now-standard wavelength.So what does it do for paper? Brightpaper makes colors dazzle. A high degreeof brightness also enhances contrast,brilliance, snap and sparkle of theprinted subject. It's all the differencebetween lighting a room with a 40-w attlight bulb versus one that's 200 watts.

Warm shade


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Potlatch

W H E R E P A P E R I S J U S T T H E B E G I N N I N G O F T H E P A R T N E R S H I P

P O T L A T C H C O R P O R A T I O N , C L O Q U E T , M I N N E S O T A 5 5 7 2 0 8 0 0 - 4 4 7 - 2 1 3 3 W W W . P O T L A T C H P A P E R . C O M

2002 Potlatch Corporation Printed on Potlatch McCoy Gloss 100 lb. Cover
http://www.potlatchpaper.com/http://www.potlatchpaper.com/

behind the scenes spotlight on color theory and brightness 0

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