American Cinematographer - January 2021 - 18

SHOT CRAFT

A Bit of History

While early, extremely slow orthochromatic
film stocks required the intensity of natural
daylight to create an exposure, the need for
flexibility and variety - and, of course, the
option to shoot at night - led to the speedy
introduction of artificial sources. It began
around 1900 with mercury-vapor tube lamps
from Cooper Hewitt, a technology that was
used in street lighting at the time. Carbon-arc
flood lamps entered the ring toward the end
of the first decade of the 1900s, but by the
1920s, panchromatic film and sound recording
necessitated an end to the green-blue mercury vapor fixtures and noisy carbon-arc sources
in favor of tungsten illumination - or " Mazda
lights, " as they were called by General Electric.
These had been in use in the real world since
about 1909, but it wasn't until the early to
mid-1920s that they were adopted for use in
motion pictures.
In 1934, Mole-Richardson introduced the
Fresnel lens to incandescent sources. Simultaneous to this development, carbon-arc sources were retooled for better color rendering on
color film, but they were mostly phased out in
the 1950s. Also in the 1930s, fluorescent lighting came into vogue for industrial applications.
By the early 1950s, fluorescent technology
was being used in television studios, but was
phased out with the rise in color photography.

Types of LEDs: The Big Three
Bi-Color Emitters
One of the extraordinary benefits of LEDs is the
ability to achieve multiple colors in one fixture.
Instead of having to swap between tungsten
and HMIs or change out tubes in a fluorescent
fixture, a single LED can produce both daylight
and tungsten colors. The bi-color units are also
purported to be able to - through a mix of the
two colors - re-create any Kelvin temperature
between 3,200K and 6,500K.
18 / JANUARY 2021

From the AC Archive: A look at HewittCooper mercury tubes in use in a studio in
1922 (left), plus vintage lighting ads from
1937 (top middle), 1932 (right) and 1991
(bottom).

The need for flexibility and
variety led to the introduction
of artificial lighting sources.
During the 1960s, Osram introduced hydrargyrum medium-arc iodide (HMI) sources into
filmmaking, which were slow to come to the
U.S. because the conversion from 50Hz to 60Hz
took some time. Fluorescent lighting made a
comeback in the 1980s and '90s, pioneered in

But not quite. As noted above, the Planckian
locus is a curve. If we have two colors of diodes
in a fixture, then we can create two points in
the CIE color space (each has its own X/Y coordinates), but as we blend between them at various intensities, we can only travel on a straight
line of colors between the two. This means that
as the two blend toward the middle of their respective color temperatures, they get further
away from the locus and, hence, shift more toward magenta and away from the color fidelity
of being on the locus. Correcting this, in most

no small part by gaffer Frieder Hochheim, who
later founded Kino Flo and became an ASC
associate.
Though the industry had brief flirtations
with plasma lighting in the 1990s and 2000s,
it's the evolution of LED technology that's leading the way into the future.
At each of these technological milestones,
the American Society of Cinematographers
was there to investigate the viability and
efficiency of these new lighting sources.
Each of these new tools also spurred intense
discussion and examination by the Society to
facilitate their integration into film production.
As AC subscribers now have digital access
to all 100 years of the magazine's coverage,
you can dive in whenever you like!

cases, requires adding gel, either plus or minus
green, to shift the color back onto the curve.
(See " Problem and Time-Tested Solution, " page
20.)
RGB Emitters
A step beyond a bi-color unit is the RGB LED
fixture, a single unit that works on the additive
color system and simulates the full range of the
visible spectrum through the combination of
red, green and blue light. (See Shot Craft in AC
Jan. '20).

American Cinematographer - January 2021

Table of Contents for the Digital Edition of American Cinematographer - January 2021