American Cinematographer - September 2019 - 16

Burum also worked with split-field diopters for a number of shots in Carlito's Way,
directed by Brian De Palma and starring Al Pacino.

single image. There are also "slot"
diopters where the filter covers most of
the frame but has a small slot cut into it
- the opposite of a strip. Tiffen, for
example, refers to these as Letterbox
diopters.
For a moment in Hoffa - directed

by and co-starring Danny DeVito -
Burum effectively created his own
"letterbox" diopter. In the scene,
DeVito's character is having a tense
conversation with John C. Reilly's in the
theater wings, while Bruno Kirby can be
seen in the background, entertaining an

audience from the stage. To hold all
three actors in focus simultaneously, the
lens was focused on Kirby on the stage,
while DeVito and Reilly - positioned on
opposite ends of the frame - each had
his own split-field diopter. (Burum
received an Academy Award nomination
for his work on the film.)
Some split-field diopters come in
circular frames, but rectangular frames
tend to be easier to accurately position
in front of the lens via a geared or sliding
filter tray in the matte box. In some
cases, such as with Lindsey Optics' RotaSplit diopters, the diopter is circular in a
square filter tray with built-in gear
wheels on the top that allow the diopter
to be rotated to any degree.
At times in his work, Burum would
use a "dynamic" close-up attachment,
floating a diopter in or out of the frame
as the camera or talent moved. In Carlito's Way, for example, there's a scene in
which the title character (played by Al
Pacino) is watching Gail (Penelope Ann
Miller) on the dance floor when a waitress comes up to talk to him; Carlito's
attention is then divided between the
conversation and Gail's dance. To hold
focus on both, Burum focused the lens
on Miller in the background and used a
split-field diopter to hold the waitress in
close focus; then, as the conversation
with the waitress ended, Burum zoomed
in on Miller, and as the field of view

Quick Tip
Strictly speaking, when physically measuring focus distance to your subject you should always take the measurement
from the entrance-pupil position of the lens. Unfortunately, that position is not always known, and it can move within a lens
based on focal distance and zoom setting - hence the common practice of always measuring to the camera's focal plane, a
fixed position that doesn't change. In most typical working distances, the few inches of difference between the focal plane
and entrance pupil have no effect on the resulting sharp-focused subject. When working in extreme close-focus situations,
however, those few inches can make a difference in whether or not your subject is in focus.
When using diopters, the entrance pupil is magnified and, effectively, advanced forward beyond its natural position in
the taking lens. The common practice, therefore, is to take your focus measurements from the diopter itself at the front of
the lens, not the focal plane. While this is still somewhat of a cheat, it works most of the time. But always double check with
eye focus and a high-resolution monitor - and if you're shooting film without the benefit of a high-resolution video tap, test,
test, test before you shoot to determine the appropriate revised entrance-pupil position from which to measure in each situation.
"It's important to do a series of tests with the lenses that you're going to be working with," Stephen H. Burum, ASC
advises. He encourages focus pullers to make their own charts with details specific to the lenses actually being used. "Every
brand of lens is a different physical length, so the chart has to be specific to the lenses that you're using." He also cautions
that "if the diopter is in a matte box, it won't be as close [to the lens] as a diopter that screws onto the lens."
For a full "Plus Diopter Lenses Focus Conversion Table," please refer to the American Cinematographer Manual (page
752 in the Ninth Edition, or page 818 in the 10th).
16

September 2019

ASC 100th Anniversary

American Cinematographer - September 2019

Table of Contents for the Digital Edition of American Cinematographer - September 2019