American Cinematographer - October 2017 - 18

DIY
The (Almost) Instant Diffusion Frame
While working on the book A Shot in the
Dark: A Creative DIY Guide to Digital Video
Lighting on (Almost) No Budget, I spent hours
perusing the aisles at my local hardware store,
looking for ideas for inexpensive DIY grip gear. I
was particularly excited to find a window-screen
frame-replacement kit, which can be made to
serve as an effective alternative to a traditional
diffusion frame or net.
The kits come in different sizes that can
be cut down to fit your specific window; I
bought the largest one I could find and built it
without cutting it, creating a 3'x3' square. Once
the frame is assembled - a simple process of
sliding-in corner joints and then attaching the
sides - you can fit it with any kind of material
that you desire. For a diffusion frame, I reached
for a large cut of liner's silk, an inexpensive silklike material that comes in many different
shades - bright white or off-white are most
useful - and performs like a classic Hollywood
silk but at a fraction of the price. Alternatively,
you can use actual window-screen material to
create a net, or you could use black silk or
thicker muslin - whatever you want!
The material is secured in the frame with
a length of retaining rubber. To get this in place,
it's best to have a spline roller - which looks like
a small, unsharpened pizza cutter - but you
can also work it in with just a flathead screwdriver. I wouldn't recommend using any kind of
paper diffusion, as it will tear easily when working in the spline. Fabric - such as silk, bedsheet
or Grid Cloth - is the best bet.
These frames aren't rugged enough to
handle rough conditions, and if not handled
with care, they
won't last long.
However, they are
inexpensive and
quick to make.
The screen kit was
$10 and the liner's
silk, which can be
found at any
fabric store, was
$3. Total cost:
$13.
- JH

October 2017

This diagram illustrates the light rays' path in an ellipsoidal reflector spot (ERS) fixture, from
the light source, to the ellipsoidal reflector, and through the conjugate focal point.

Because of their flood and spot
functions, Fresnel units are versatile fixtures
that can adapt to coverage and intensity
needs without requiring additional hardware, and since the rays of light are
refracted in a focused pattern, they can be
easily cut with flags. They require a single
source such as an incandescent bulb or, in
the case of an HMI, a gas-discharge lamp;
because they employ a single source,
there's no danger of multiple shadows.
The Fresnel is a true workhorse in
motion-picture lighting. Having a few of
them on-hand in different sizes and
wattages will keep you covered in an array
of lighting scenarios you might encounter.
ERS
Next up is the ellipsoidal reflector
spotlight (ERS). Often referred to by the
nickname "Leko" (based on Strand Lighting's Leko Lite) or, sometimes, "Klieg light"
(after the erstwhile Kliegl Brothers Universal
Electric Stage Lighting Co.), you might
know this fixture as a Source Four, which is
the name used by Electronic Theatre
Controls (ETC), which manufactures a highquality, advanced and versatile version of
the ERS. ERS fixtures are great for spotlighting an object in the background, giving a
specific shape to the light on set, or introducing a pattern to the light.
An ERS features a built-in reflector in
the shape of half an ellipse. The light source
is placed within the elliptical reflector, and
the light rays are bounced off the reflector
American Cinematographer

surface into a single point called the conjugate focal point, or CFP. With lenses placed
just past the CFP, the rays are then refracted
and focused into an intense, concentrated
spotlight that can be projected over great
distances.
Additionally, an ERS features an aperture - called the gate - just before the
CFP that cuts off beams of light and forms
the shape of the light that will be projected
through the lens. The gate has four
adjustable shutters: solid metal blades that
can be inserted into the gate to further
shape the beam of light. This is like building
four flags into the fixture in order to cut the
light off of unwanted areas and shape the
beam into almost any simple linear shape.
As any interruption of the light at the
gate's position can be precisely focused in
the fixture's projected beam, we can insert a
template, or "gobo," into the fixture; a
gobo is any object that cuts or shapes light.
Whatever pattern is cut into this gobo - a
window frame, tree branches, etc. - will
be projected onto the surface being lit.
GAM, Lee, Rosco and other manufacturers
offer templates for almost any pattern
imaginable.
All ERS fixtures feature a series of
lenses that can be adjusted closer to or
farther from the CFP to focus or defocus the
beam as desired. ERS units come in various
sizes, generally described by the diameter of
the lens, the length of the barrel, and the
field of projection for the beam angle (the
center, hottest portion) of the light. The

Table of Contents for the Digital Edition of American Cinematographer - October 2017