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 The
faster the film the more light the cinematographer uses. Although a paradox
that statement is essentially true. A clearer statement would be to the
effect that as better tools become available, the cinematographer uses
them to improve his work. With an increase in film speed he may use half
the light or he may double the amount. His goal is dramatic effect and
he does it with light. A study of the advances in cinematography during
the past ten years will more than justify his position.
The
new Mole-Richardson Type 450 carbon arc lamp was designed and built as
a result of the insistent demand from cinematographers for a light source
with twice the intensity of the present Type 170 M-R Hi-Arc. The type
of carbon trim, current, voltage, and optical system were all chosen or
designed with the requirements set forth by the cinematographers themselves
as a goal.
Fig.
1 illustrates how these requirements were met. With a 48° beam spread,
which is approximately full flood, the Type 450 gives exactly double the
lumens of the Type 170. With 12° beam
spread on the Type 450 and 10° beam spread on the Type 170 the ratio
is further increased.
Fig.
2 illustrates, the comparison between the Type 450 and the Type l70 lamps
in light intensity, Within a 20 ft. diameter spot. This increase in penetrating
power gives the cinematographer a lighting tool with which he can produce
streak lighting, shadow detail, penetrate the deepest of sets, boost high
levels of daylight or create a "one source" lighting effect even when
the general set light levels are high. By operating at full flood position
he can cover areas with the one lamp.
Fortunately
this 100 per cent increase in light output was obtained with only 50 per
cent increase in current. The Type 450 unit operates with a 16mmx22 super
high intensity positive MP studio carbon and a 17/32" x 9"cored Orotip
negative carbon burning at 225 amperes and 75 arc volts, whereas the Type
170 lamp burns a 16mmx20" MP studio positive carbon and a 1/2"x8 1/2"-
MP studio negative carbon at 150 amperes and 67 volts.
The
newly designed Fresnel type condenser lens on the Type 450 lamp has a
curved surface and is of 24" diameter which gives it a greater light pick-up
angle than the 20" diameter flat surface condenser of the Type 170. The
main advantage of the larger diameter curved surface condenser is that
it provides for a greater arc-to-condenser distance at various beam divergencies,
thereby minimizing the danger of condenser breakage from the increased
heat.
The
Type 450 lamp head is not just a modification of the Type 170. The 100%
light increase and 50% current increase created problems of heat transfer
and ventilation requiring a radical departure from the conventional rotating
high intensity lamp design.
The
arc control motor, motor rheostat, arc switch and pin plugs were all removed
from the beat of the body of the unit and located in a separate compartment
on the rear lamp casting. Inasmuch as the balance of the carbon feeding
mechanism is mounted on the front of this same casting, the whole forms
an integral unit which may easily be removed for servicing.
By these
changes in design it was possible to build a lamp head, capable of continuous
operation at 225 amperes, with no increase in length, only 4"increase
in diameter and slight increase in weight over, the Type 170.
The
color quality of the light from the Type 450 is essentially the same as
from the Type 170 and when used for daylight balance, as in shooting color,
the unit should be equipped with a Y-1 filter.
A number
of the Type 450 lamps have been completed and are now undergoing a production
test routine in the studios. Any additional knowledge gained from this
preliminary work will be incorporated into the final design which will
be set for production in the near future.
In order
to receive the most benefit from this production work Directors of Photography
and A.S.C. members who are using the new Type 450's are being interviewed.
Some of their comments are paraphrased as follows:
John
W. Boyle: "We used the 450 on a Cinecolor picture at Hal Roach. We were
on a theatre set and wanted a shot of the audience from the stage with
a light level to indicate that the theatre was well illuminated. We set
the 450 on the stage and adjusted the beam spread to cover an audience
of about one hundred and fifty people. With the use of scrim we were able
to control the light intensity from foreground to background."
"What
other lamps were used?"
"We
used a few lights here and there for balance, but the main source of light
was from the 450. In that particular shot the 460 replaced several other
lamps because of its ability to carry from the stage to the back row of
seats."
Wilfrid
Cline: "We used the 450 on a Technicolor dance number at Warner Brothers.
It is an excellent source as a main front light unit when operated at
full flood position. We adapted a set of venetian blinds to it and were
able to dim it in that manner.
"A most
interesting use, however, was for or a special effect we were after and
were able to accomplish because of the 450. We wished to project a 20-foot
diameter star pattern onto the floor with sufficient intensity to overcome
the general set level and to enhance the effect by gradually dimming the
light around the star pattern. We hung the 450 about 30 feet above the
set pointing straight down. A few feet below the lamp we hung a board
with the star shape through it. The effect was perfect."
"Did
you try a Type 170 for that effect!"
"Yes,
we did, but it was not powerful enough."
NOTE:
Fig. 2 shows that the Type 450 will deliver three times as much light
as a Type 170 in a 20-foot diameter circle at 30 feet distance.
Sol
Polito: "We wanted a lamp for a particularly large set to be shot with
black and white film at RKO-Pathe Studios. It covered the entire area
of stage 15, and we shot from the adjacent stage 14. There was considerable
open area in the foreground with few characters and a lone wagon. The
problem was to find a single source of sufficient penetrating power and
light volume with which to illuminate the entire area in order to obtain
single shadows. The 450, adjusted to full flood position, was placed about
30 feet and 50 to 60 feet from the action. It did the job in fine shape"
"You
used other lamps, of course?"
"Yes,
for fill light, balance, behind windows, etc., but the main source of
illumination was the 450. It produced just the effect we were after. In
fact we had to use scrim in certain areas to cut down the light."
"Would
you say that most of the photographic light came from the 450?"
"Yes,
it did in this particular shot. As a matter of fact when you light that
lamp everything else seems to be out."
Ray
Rennehan: "We are using the 450 on a current Technicolor picture at Paramount.
On certain shots it provides the main body of front illumination. It is
possible to cover an area with the 450 and build up to it with the other
sources in a more satisfactory manner than if we used a source of lesser
power. This is particularly true if a one-source effect is desired.
"The
need for a more powerful lamp has long been recognized. This does not
indicate that more overall light is required than is available at the
present time- As a matter of fact it could mean that in certain cases
the power used for a given shot may be less because of the wider latitude
of lighting media."
The
Type 450 lamp is not expected to revolutionize the art of cinematography.
It is a new and more powerful tool with which to make better pictures.
Its increased power may mean double the light on the set, and it may mean
half of the light. In either ease it is a small factor. The picture
is the thing.
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Fig 1. Chart indicating relative illumination characteristics of
MR-type 450 lamp burning the 16mm super H.I. studio positive at
225 amperes, and the MR-type 170 lamp burning the 16mm H.I. studio
positive at 150 amperes.
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DISTANCE FROM LAMP IN FEET
Fig 2. Typical curves showing illumination at center
of 20-foot diameter spot at various distances from MR type 450 lamp
burning the 16mm super H.I. studio positive at 225 amperes and MR
type 170 lamp burning the 16mm H.I. studio positive at 150 amperes.
* The diameter of the spot is defined as the diameter at which the
illumination is 10% of the maximum illumination present at the center
of the spot.
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