Summary-This report contains information on three phases of studio lighting as follows: I. Various types of new equipment which have been recently developed and used are described and illustrated. II. New uses for standard commercial lamps are discussed. III. The results of tests conducted to determine the effect of variation of power-supply voltage and lamp maintenance upon color rendition of 16mm commercial Kodachrome are given.

I. NEW EQUIPMENT

Special Effects with Remote-Controlled Shutters

SHUTTERS OF THE Venetian-blind type have been used for some time on set lighting lamps for dimming, color-changing, simulating the turning off and on of lights in a room, and various other types of special effects. Wherever they have been used in groups a need for exact synchronization has been indicated. With manually operated shutters a man must be located at each lamp to operate his respective shutters upon receipt of a cue and with this mode of operation it is impossible to have all of the shutters operate in unison. A remote-control system was indicated where all the shutters would operate in synchronism and from one control point.
In response to this need the electrical department at the Metro-Goldwyn-Mayer Studios developed a direct-current self-synchronous system for remote control of the shutters in groups. They have obtained interesting results in special-lighting effects such as the simulation of the sunrise following the rainy season in "The Yearling," and the Easter sunrise service in the "Three Darling Daughters." -The lighting setup for the sunrise effect in "The Yearling" involved remote control at an extremely slow speed with as many as 40 individual shutters operating in exact synchronism.
Direct-current self-synchronous remote-controlled shutters are now available (see Fig. 1) and are being successfully used in the studios. The shutter is an improved design of the Venetian-blind type, which has been used in the studios for several years. The shutter motor is essentially a direct-current self-synchronous motor constructed integral with a gear-reduction unit. The transmitter is in the form of a rheostat whose brushes can be manually rotated by a handle external to the rheostat housing. Approximately 180-degree motion of the handle is required to rotate the remote-controlled shutter blades through their full travel.

Fig. 1 -- Remote-controlled shutter shown mounted on a set-lighting arc lamp, connected through cables and plugging box to a transmitter capable of positioning up to 15 shutters, as manufactured by the Mole-Richardson Company.

Friction slip clutches are provided in the shutter-motor gear reduction boxes for synchronization. After a group of shutters have been set up and connected to the direct-current supply, one complete movement of the transmitter operating handle from its open to closed position, or vice versa, will result in the synchronization of all the shutter blades of a connected shutters. A reversing switch is included on each shutter motor. With this switch thrown to the "normal" position the shutter blades will follow the movement of the transmitter operating handle in the normal fashion; that is, moving the transmitter handle to the open position will result in the blades' opening, and movement of the transmitter handle to the closed position will cause the shutter blades to close. If the switch on a particular shutter motor is thrown to the "reverse" position, the operation of the blades on that shutter will be out of phase with the remainder of the units. Thus it is possible to cause some shutters to close as others open and vice versa in any desired combination.
Each of the transmitters is capable of operating one to fifteen shutters. The standard equipment includes a plugging box connected to the transmitter with 50 feet of 3-conductor rubber-covered cable. Various shutters can be plugged into this plugging box with their respective 25-foot cables, or a group of shutters can be interconnected in a series-parallel arrangement to the plugging box. If it is desired to operate more than 15 shutters in a unit, provisions can be made to operate more than one transmitter from a single handle.
A direct-current system has advantages over an alternating-current system in the following respects:

(1) Direct current is always available as a power supply on the sets whereas in some locations there might be no alternating current.
(2) The direct-current control motors produce no noise such as might be present in the form of a 60-cycle hum in the alternating current motors.
(3) The direct-current self-synchronous motors cannot be damaged by overload if stalled out of correspondence.
(4) The direct-current system requires three conductors to each motor whereas an alternating-current system would require five.

The position of the shutter blades follows the position of the transmitter and the speed of the shutter-blade movement follows the speed of the movement of the transmitter. For dimming purposes the blades can be made to move as slowly as it is possible to turn the transmitter. There is a limiting maximum speed at which the system can be operated without having the shutter blades fall out of step or lose synchronism with the transmitter. However, in actual service with the shutters simulating the turning off and on of lights in a room from a snap switch, it has been determined that the shutter blades will travel from their full open position to their full closed position or vice versa in four frames on the film. Hence, the time required for the blades to rotate through their full travel is one sixth of a second. This speed is adequate for any situation which is anticipated in studio lighting effects.
"Snap-switch" operation of the remote-controlled shutters was well executed in a recent production at the Warner Brothers studios.

Fig. 2-A group of remote-controlled shutters mounted on arc lamp rigged for studio set lighting. Courtesy of Electrical Department, Warner Brothers Pictures, Inc.

In a scene in this picture an actress walks out of a living room, turns off the living-room lights, and enters a bedroom. She walks to the bed and turns on the bed lamp, then back to the wall switch and snaps off the main bedroom lights. The actress goes to bed and shortly thereafter turns off the bed lamp, at which time moonlight appears through the bedroom window. The set lighting for this rather complicated sequence of light changes was accomplished by means of the remote-controlled shutters on the set-lighting lamps operated by special motor-driven transmitters developed by the Warner Brothers electrical department. The control circuits for the shutters were connected to and operated by the various light switches which the actress operated in the scene.

Fig. 3-MoIe-Richardson Type 400 arc lamp.

The synchronization of the variations in lighting with the operation of the various light switches was perfect, and there was no possibility of missing a cue.
The remote-controlled shutters were again used in a recent Warner Brothers production to simulate the illumination in a room coming through a window from a flashing neon sign. The neon sign, complete with its flashing mechanism, was installed on the set outside of the window. Its operation was such that it flashed from red to white, to green, to white, to red, to white, and so on. Lamps were rigged on the set with red filters to stimulate the red portion of the neon-sign lighting, green filters to simulate the green portion, and no filters to simulate the white portion. Remote-controlled shutters operated by the specially constructed motor-driven transmitters were mounted on the lamps. The circuits between the transmitter and the shutters passed through relays which were electrically operated by the neon flashing mechanism. Thus the operation of the various shutters was automatically synchronized with the flashing mechanism of the neon sign, and a perfect lighting illusion was created.

Small Arc Lamp for Close-to-Camera Work

A small lightweight arc lamp is now available which can be located close by the camera lens or concealed behind relatively small objects (see Fig. 3). It is essentially one half of a Type 40 Duarc and when supplied with a reflector and diffusing glass will produce an intensity of 125 foot-candles at 10 feet with a spread of about 140 degrees. It can also be equipped with a spherical mirror and Fresnel lens to produce an intensity of 250 foot-candles at 10 feet with a narrower spread of about 80 degrees. The arc current is 40 amperes. The lamp weighs about 35 pounds and is capable of being operated in either the vertical or horizontal position. A separate grid unit is located about 25 feet from the lamp.
This small arc lamp has been used in several productions close by the camera for close-ups to produce a soft front fill light to wash out undesirable shadows, or in locations slightly on one side of the camera to give a close-in key light. Being small in size it lends itself to concealment behind relatively small objects, columns, or beams.

The "Brute" Lamp

The Mole-Richardson Type450 "Brute"¹ (see Fig. 4), having twice and in some cases more than three times the illumination of any single source previously used, has proved itself to be an extremely valuable tool. One of its chief uses is to create an illusion of "one-source" lighting, casting single well-defined shadows through the complete scene of action. The Brute has in numerous cases made it possible to illuminate sets adequately with fewer lighting units than otherwise would have been required. For large, deep sets this lamp can provide the required level of illumination throughout the full depth of the scene. It has also been found to be useful for providing "booster light" on outdoor sets.

Small Incandescent Bulbs for Special Effects

One of the lamp-manufacturing companies has developed and introduced a small line of incandescent bulbs for special-effect lighting. One of these lamps is known as catalog No. 25S6 (see Fig. 5) and has a 25-watt, 115 to 125-volt filament placed in a bulb 3/4 inch in diameter and about 1 1/2 inches long. This motion picture effect lamp has an average life of 50 hours.

Fig, 4-Mole-Richardson Type 450 "Brute" Molarc.	Fig. 5-Small special-effect incandescent lamp, Catalog No. 25S6.

Another has a 25-watt, 50-hour filament placed in a small bulb 1 1/2 inches in diameter having a built-in reflector and is known as catalog No. 25R12DC (see Fig. 6). It is in effect a miniature reflector photoflood. This lamp will produce a light intensity of approximately 75 foot-candles at 20 inches.
Both of the above midget-size lamps lend themselves to being concealed behind small objects and have a number of special uses for small lighting effects.

II. NEW APPLICATIONS OF STANDARD COMMERCIAL LAMPS

Airplane Landing Lights Used for Automobile Headlamps

Fig. 6-Small incandescent reflector lamp, Catalog No. 25R12DC.

Out-of-door scenes simulating night conditions are frequently made in broad daylight with a filter over the camera lens in order to obtain a night effect but still have the entire scene illuminated so as to produce good definition on the screen. Ordinary automobile headlamps under these conditions do not appear lighted unless perhaps the headlights are aimed directly at the camera. Many attempts have been made made to illuminate more brilliantly the headlight lens by paralleling filaments in a bulb, using 50-candlepower bulbs, overvoltaging filaments, etc., with mediocre results.

An outstanding successful method is to use sealed beam-type airplane landing lamps developed for military craft which are rated at 450 watts and fit the regular sealed beam-lamp assemblies on automobiles (see Fig. 7). Such a lamp is so powerful that in a recent color picture the headlight beams on an actress's dress showed clearly on the screen as she walked in front of the automobile even though the picture was actually taken in sunlight with the camera filtered to simulate a nighttime setting. This lamp is available as a No. 4540 which is rated at 450 watts, 13 volts and No. 4541 which is rated at 450 watts and 28 volts. Both lamps have a 25-hour average life.

Fig. 7-Airplane landing lamp Catalog No. 4540.

Photo Reflector Lamps Applied for Fill-Light Illumination

A reflector photoflood designated as the RFL2 (see Fig. 8), a 500-watt, 115- to 120-volt floodlamp, was used in 1947 much more extensively than in the past for delivering a flood of light used for fill-in purposes on locations. Occasionally where greater distances were involved or where small key-lighting effects were desired, the RSP2 photospot was used. The photospot lamp is identical in size, shape, wattage, and color temperature with the photoflood but has a much narrower and several times more powerful beam. Generator capacity is often at a premium on locations and although these reflector lamps have a short life, they can be employed advantageously under such conditions to obtain a relatively large amount of light with the limited power supplied. Being light in weight, these lamps simplify the transportation problems but however, do not allow the flexibility of control of illumination which is characteristic of the focusable Fresnel lens units.

Fig. 8--The RSP2 photospot, left, and the RFL2 photoflood, right.

III. RESULTS OF TESTS PERTAINING TO COLOR RENDITION OF 16-Mm COMMERCIAL KODACHROME

Effect of Arc-Lamp Supply Voltage Upon Color

Tests were recently conducted at the Mole-Richardson Company in conjunction with the Eastman Kodak Company to determine the effect of variations in arc-lamp conditions upon the color rendition of 16mm Eastman commercial Kodachrome (3200-degree Kelvin) film. The tests were made using an M-R Type 170 Molarc lamp with a new Y-1 filter for illumination with a Wratten No. 83 filter and the proper emulsion color-correction filter over the camera lens. The normal current drawn by a Type 170 arc is 150 amperes with a line voltage -of 115 volts. Photographic tests were made under the following three sets of conditions:

(1) The line voltage was varied from 108 to 118 volts with the carbons adjusted so that the arc current was maintained at the normal value of 150 amperes in each take.
(2) The line voltage was maintained at 118 volts and the arc current varied from 134 to 158 amperes by adjustment of the position of the carbons.
(3) The arc lamp was adjusted for normal operation of 150 amperes with a line voltage of 115 volts, and then the line voltage was varied from 108 to 118 volts with arc current varying in correspondence with the variations in line voltage.

In each take the lamp was spotted or flooded as necessary to maintain the same light intensity of approximately 1200 foot-candles on the subject. No noticeable visual effect in color was observed under the above variations of arc-lamp illumination.
The Committee plans to make similar tests, the results of which can be published in a subsequent report, to determine the effect of variations of incandescent lighting on the color rendition of commercial Kodachrome film. Information published in the Photo-Lab Index² indicates that the color temperature of incandescent illumination will not visually distort the color on the film unless it departs as much as approximately 100 degrees Kelvin from the correct value. The color temperature of photographic incandescent lamps changes from the rated value about 10 degrees Kelvin for each volt difference between the actual supply voltage and the rated voltage of the lamp. Hence a 115-volt lamp operated at 125 volts will have a color temperature which is 100 degrees Kelvin higher, or if operated at 105 volts its color temperature will be 100 degrees Kelvin lower than the rated color temperature.
The above tests would indicate that color is not appreciably affected by the usual expected operating variations encountered with illumination. However, the importance of maintaining correct line voltage should not be minimized. Even though line voltage can vary to a certain extent without appreciably affecting the color, such variations definitely affect the intensity of illumination and the efficiency of arc operation. Line voltage therefore should be maintained as closely as possible to the normal value in order that variations in light intensity and abnormal are operation are kept to a minimum.³

Effect of Maintenance of Arc Lamps Upon Color

The importance of maintaining clean arc-lighting equipment was demonstrated in split-screen tests recently conducted at the Mole-Richardson Company in conjunction with the Eastman Kodak Company. A subject was illuminated with a clean M-R Type 40 Duarc lamp and photographed on Eastman commercial Kodachrome (3200 degrees Kelvin) film with a Wratten No. 83 filter and the proper emulsion color-correction filter on the camera. This exposure was made on one side of the film. The other half of the film was later exposed with all conditions remaining the same except that the clean Duarc was replaced by one whose front-door glass and reflector were considerably contaminated with the arc-flame residue material which accumulates with time if the lamps are not properly maintained. This split-screen test clearly indicated that the color in the picture tends strongly toward the yellow if dirty lamps are used for illumination. All arc-lighting equipment should be kept clean to avoid such off-color effects.

REFERENCES

(1) M.A. Hankins, "Recent developments of super-high-intensity carbon-arc lamps," J. Soc. Mot. Pict. Eng., vol. 49, pp. 37-47; July, 1947.
(2) Photo-Lab Index No. 10-ILL-20, Quarterly Supplement No. 28 (replacement page), pp. 10-13, published by Morgan and Lester, New York, N.Y.
(3) "Report of the Studio Lighting Committee," J. Soc. Mot. Pict. Eng., vol. 45, pp. 249-260; October, 1945

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