American Cinematographer - December 1988 - 94

optical printer cameraman optimum control
of the matte and the image on a frame-by-

the other side when the shot ended. Be¬
cause we have incorporated motion control

frame basis.
The

technology in

importance of this control
became apparent when Edlund described
two points about lenses. "When you are
photographing a large area of a scene that
is one particular color - in our case it's
blue
then you are going to get a certain
amount of flare in the lens from that light. It
doesn't matter what lens you have or what
coatings are on the lens. That's another
reason for masking off any unnecessary
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Therefore, you may photograph a
or

with the

film

lens, the same cam¬
the live action director of

same

as

photography, but if you have that over¬
whelming blue fill, you cannot ever really
time the effects of that light 'veiling' out.
"The second point is camera¬
men are always after manufacturers to
develop very fast lenses - T 1.4s, for in¬
stance, and wide angle lenses. In order to
give a cameraman a fast lens there are
certain trade-offs that must be made. One of

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those trade-offs has to do with the chromat¬
ic aberrations in the lens. Chromatic prob¬
lems always get progressively worse as you
get further towards the corners of the lens
field. You may have perfect chromatic cor¬
rection in the center of the lens, but as you

get out to the edge, the colors start focusing
on

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slightly different planes. You don't notice

that, generally, when you are watching a
film, but when you are extracting a matte
from the very far end of the color spectrum,
the blue part of the image can actually turn
out to be a little bit larger
from the other colors.

than the images

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up.

It's pretty amazing to think about, but
is available in off-the-

that kind of precision
shelf technology."
As for

simply put, if you are
photographing an object that is in the center
of the screen, then the matte will be a

white beachball and

develops

You fit the matte

on one

side and

the screen she has a matte line on one side.
In the past, you would have opted to fit her
would have

she

a

matte line on one side when

began her walk

06109 U.S.A.
December 1988

across screen

and

on

for checking the light.

According to Edlund, "When you
light you want a densitometer
reading of .08 to .12 in the red, .65 to .70 in
the green and about 2.2 in the blue on the
negative. You can shoot that at T22 with
enormous amounts of light or you can be
shooting at T1.5 with less than 25 foot
candles. None the less, you want the blue to
read at 2.2 regardless of the stop you are
shooting at and the blue reading has to do
with the brightness of the screen. To control
the brightness of the screen we use large
NDs on the screen for gross changes, and a
dimming circuit for fine tuning."
Finally, special effects facilities
have very different relationships with the
read the

film laboratories from their live action

coun¬

terparts. The professional labs are used to
develop color negative and to print and time

composites. An in-house black and

white lab is very important to the blue
screen process. "It's economically sound, of

but also we

always playing with
separations and matte
development. We can change emulsions,
dryer temperature, development time and
so on if necessary, to meet the require¬
course,

are

black and white

have

screen.

a system

The difference in blue screen photography is
what the blue screen photographer needs to
know about the light in his blue screen shot.

further outward of the other colors, which
would make its matte a little bit larger.

by the time she walks to the other side of

a grey card. One cam¬
hot-rodded Pentax meter,

a

another a digital spot meter. As in the case
of live action cinematographers, each one

our

the

has

eraman

perfect fit. But when you have a large object
that fills the frame, the matte may be
oversized slightly on the outside because
the colors aren't focusing in the same plane.
The blue is usually focusing a little bit

"Consequently, you get on the
printer and you realize that even though
you've done everything right, the matte
doesn't fit. For example, you can have a
situation where an actress is walking across

metering the light in blue

it's every cinematographer for him¬
self. Edlund has watched great, old-time
cameramen go at it with a paddle meter, a
screen,

the final

"More

in the center and live with the fact that she

The Film Group

our printer, if we have a twothousandths of an inch matte line around
the girl, we can fly the image in the printer a
thousandth this way or that way and line it

ments of each shot and with our own lab we
a

lot

more

control," explains Edlund.

In the final

analysis, then, light¬
ing for blue screen would seem to require a
book to understand. But Edlund isn't sure
that a book would help. The basics are fairly
easy to understand, but how to finesse all
the variables is the lesson of experience.
"We at Boss Film Corp. have done more blue
screen shots than I can count and we are

pretty proficient at it, but we are still not
undaunted by the process. Even if you do a
lot of work, your problems are not over. It is
difficult to do a good blue screen shot

because every

shot is different."

A
American Cinematographer - December 1988

Table of Contents for the Digital Edition of American Cinematographer - December 1988
