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August, 1953
For Colour Photograph)
HOULT, HARPER AND STAFFELL '. PROCESS PROJECTION IN COLOUR
39
Camera Stop
Lumens
f72.5 f/4.5 f/6.3
17,000— 84,000
50,000—260,000
120,000—650,000
Suitable Types of Still and Moving Projectors
We have at Pinewood excellent equipment, not only projectors but screens, screenholders, meters for assessing exposure and density, floor mirrors (for " folding " the projector beam into a compact space) and a very comprehensive range of projection lenses, from a 22-inch f/4.5 to a 4-inch f/1.4.
However, the projector is the most important single item and the three principal types of projectors will be described briefly.
The J.A.R.O. 35mm. Single-Head Projector
This is assembled on a mobile platform (Fig. 1). The main column can be extended
manually to give a rise of 30 ins. from the base.
The optical platform carries the arc lantern, the cooling cell, the relay condenser, the light-controlling shutter, the projector head and driving motor, the objective lens and the blimp assembly. Optical alignment of these components is maintained by a common keyway on which they are mounted. Axial adjustments can be made accurately and quickly without upsetting alignment. The optical platform can be tilted and panned manually.
The arc lantern is the Mole-Richardson 1250B, using a 16mm. positive carbon and a 9mm. uncoated negative carbon. The positive head assembly is water-cooled. The feed for the positive carbon is automatically controlled by a photoelectric unit and two motors. The feed for the negative (which is also watercooled) is by one motor and a variable potentiometer.
The light-beam is collected by the watercooled first condenser unit which also contains a heat-absorbing glass filter.
The second or relay condenser throws an image of the first condenser on to the gate
Fig. 1.
The J.A.R.O.
35mm. Single-Head
Projector