American Cinematographer - December 1960 - 10

WALTER STRENGE'S

QUESTIONS & ANSWERS
Need advice on a picture making problem? Your questions are invited
and will be answered by mail. Questions and answers considered of
general interest will appear in this column each month.

Q

Can the factor established for a
given filter be relied upon to apply
under all light conditions? For example:
when the sky is cloudy and a filter is
used to improve rendition of trees,
foliage or even faces?-A. D. McC-

For narration, post-recording, dubbing, timing, or
any operation involving synchronous film timing.
Two synchronous timing motors and two precision
footage counters measure your total footage and
its equivalent time in minutes and tenths.

Answer: The amount that exposure
must be increased, when a correction
or contrast filter is used, is determined
by the multiplying factor established
for the filter. This factor is governed by
1) the photographic material used and
2) the light source. Thus, when a filter
is used outdoors, regardless of whether
the sky is clear or cloudy, the factor
established for use of that filter in sun¬
light will apply.
Filter factors specified by a film
manufacturer for its respective negative
and positive stocks can be relied upon
for accurate results. In practice, the
normal exposure time (for photography
without filter) is multiplied by the
filter factor and the lens diaphragm
set accordingly.
Now in situations where quality of
illumination may be different than that
on which the filter factor has been com¬
puted, a different factor will apply. To
determine the correct factor in such a
case, it is advisable to shoot a test, or
series of tests, utilizing a neutral test
or grey-scale card for the exposure.
Generally speaking, if the factor
specified by the film manufacturer is
used and the film corectly exposed,
any filter used will render its own color
lighter and its complimentary color
darker. Thus a yellow filter would re¬
cord yellows lighter or wash them out
completely, and record blues darker.

16mm or 35mm footage 00
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Single 16mm or 35mm ^45 00
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QWhat

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Length 16"
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Length 36"

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is the simplest and most prac¬
tical method of producing day-fornight shots in black-and-white photog¬
raphy?-J. J. O.

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716

Answer: The illusion of night in B&W
photography is best produced by a com¬
bination of contrast filters and under¬
exposure. The position of the sun with
relation to subjects in the scene is an
important factor, too.
Since the sky is bright by day and
dark by night, it is the principal area
in the scene requiring correction. For

this, use any of the yellow-orange or
red filters, such as Wratten 21, 23A,
25, 29 or their equivalents. An effec¬
tive combination is a 23A plus the
green 56.
It is important to remember that
only a clear blue sky can be filtered
down for a realistic night effect; no
amount of filtering will produce the
same results when strong haze or over¬
cast exists.
Underexposure, in addition to use of
filters, should range between l1/^ and 2
stops. Where the sky is not sufficiently
blue to produce the desired effect with
filters, it is advisable to eliminate the
sky from the scene entirely by chang¬
ing the camera angle.
QI

have experienced difficulty in pro¬
ducing satisfactory traveling mattes
for live action. One method I have
tried is frame-by-frame projection ol
scenes from a fine-grain dupe, using
a Bell & Howell Standard camera with
auxiliary shutter, then making tracings
on animation paper. Cels were then
overlaid on the tracings and matte
paintings made which were in turn
photographed on high-contrast film
stock. This method proved too costly
and resulted in considerable movement
between the mattes and the live action.
In another method, I made a series
of frame enlargements, then had the lab
paint the underside black and shoot
mattes. But this method produced an¬
noying image movement, too. I use an
Oxberry printer equipped with an Acme
camera.-L. C. D.

Answer: This type of work requires the
utmost precision in every step of the
way. Your problem seems to be that
there is too much margin for matte
line error in both of the methods you
use. Satisfactory results can be ob¬
tained with the first method described
if extreme accuracy is used in tracing
the iamges and where the matte is
painted directly on the tracing with
great care, thus eliminating the need
for using the extra cel.
We recommend for study the article
"Special Photographic Effects In Mo¬
tion Pictures," which appeared in our
October, 1957, issue, and of which re¬
prints are available at 25(2" per copy.
Other articles of interest on this sub¬
ject appeared in our November, 1960,
issue (pages 668 and 670). ■

AMERICAN CINEAAATOGRAPHER
American Cinematographer - December 1960

Table of Contents for the Digital Edition of American Cinematographer - December 1960
