American Cinematographer - January 2005 - 94

The

Color-Space Conundrum

Top left: The
human

tristimulus color

space model
resembles a
cone or

the

shape of the
Hollywood
Bowl's shell.

Top right: The
CIE's 2-D

chromaticity
diagram.

Other theories

were

that

a

color

based

on

atoms

that constituted it,

was

the smoothness of the

color consisted of

or

that

quantities of

energy where white was pure energy
and black had none. While investi¬

gating color mixtures, Aristotle
offered philosophical waxings that
were

also well off the track, but his

approach at least began to steer the
concepts in a better direction. As the
story goes, one afternoon Aristotle
spied some daylight hitting a white
marble wall, and he held up a yellow
glass fragment. The daylight that
passed through the glass and struck
the wall turned yellow. He then held
a blue
glass fragment between the
yellow glass and the wall. The result¬
ing light on the wall surface was
blue, yellow and green. He therefore
surmised that blue and yellow create
green when mixed together, which
isn't quite true when it comes to
light. Rather than mix to form
green, the dyes in the glass
subtracted portions of the light
until all that was left to pass through
in

a

certain spot was green.
Well over 1,500 years

90

January 2005

saw

one

that led him

to

formulate the

Universal Law of Gravitation
turned his attention

allowed him

placed

to see

to

the

-

and

light that

said fruit. He

prism in front of a pencilof sunlight, which,
because of a prism's variable refractance properties, caused that white
light to disperse into its component
frequencies: red, orange, yellow,
green, blue, indigo and violet, in
ascending order from lower to
higher in wavelength. Wavelengths
of visible light range from 380
thin

a

beam

nanometers to 760 nanometers,

and

the

length of a wave affects its color.
wavelength, such as that of
violet, has a higher frequency-that
is, it cycles faster with less distance
between peaks in the wave. Newton
didn't get this far in his thinking,
however
he did pass the compo¬
nent light through an upside-down
prism, which reconstituted the
frequencies into white light.
A shorter

-

Rainbows aside, all radiant
energy

is "colored." The colors that

we can see

fall within the visual spec¬

and this spectrum makes up
what we commonly refer to as light.
trum,

passed

before Sir Isaac Newton ate the

apple he

the

fall from the tree

-

An

example of a higher frequency
just outside the bounds

that radiates

of the visual spectrum

is ultraviolet.
Although often referred to as ultravi¬
olet light, that phrase is a misnomer
it is actually what we call ultravio¬
let radiation. If you can't see it, it can't
be light. Bees can, so UV is light to
them. Can you describe the color of
ultraviolet, a color you cannot see?
(And don't say purplish, based on the
groovy black light you once had in
your dorm room. That novelty's
high-UV-output fluorescent tube
allows some visible violet light to
pass through so you would know
that it is on.) UV-A energy also is
emitted but can't be seen. Only the
effect this frequency of energy has on
-

certain substances

can

be

seen, caus¬

ing them to fluoresce. (Rest assured,
the tube doesn't allow the shorter

wavelength UV-B and UV-C
frequencies to pass through and
cause

skin cancer.)
An

example of a lower
frequency is infrared radiation.
When shooting with black-andwhite infrared film,

a

stock that has

a

higher sensitivity to the infrared
spectrum, the lens focus must be set
differently than you would for visible
light because the glass does not bend
the longer wavelengths as much.
American Cinematographer - January 2005

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