Movies for TV - Early Television Foundation

LIGHTING 149
temperature, and sometimes by their wave length. In this manner,
irrespective of the type of light-producing unit, it is simpler to
obtain an idea of the actual effect of the lights proposed to be
used. In addition, the old system of referring to the wattage rat-
because the
ing still exists and probably will for a long time yet
latter is so convenient when it is necessary to calculate the amount
of power required for any given production. If the watts consumed
by each unit are known it is the easiest thing in the world to add
them up and produce a figure which will give
the total amount
of power required to provide the set with the maximum lighting
required during the show. Then the cable sizes can be determined
for the lighting and power supply.
But for planning the lights to be used, wattage alone is no help.
Some of the lamps may be the cold light type; that is, fluorescent
lighting. This has a very high efficiency
and is much more con-
venient than the arc or incandescent for it generates considerably
less heat. With less heat generated, the air-conditioning system
has less work to do, power is saved, and the working conditions
for actors where there is no airconditioning are improved.
The color response of the lenses used is important. Color cor-
rection has been mentioned elsewhere, but it should be discussed
again. If a light has a large number of different colors in it and
the lens is not corrected for color, each color will cause its own
color image to focus with a different setting of the lens control.
This means that while red is in focus, blue may be slightly out,
together with green. Another way of putting this is to say
that the
lenses used in television work are not corrected for both normal,
visible light and infrared or invisible light, and if we mix the light
types trouble is likely to result due to double or split focus. (Split
focus is an average focus in which the cameraman tries to do
justice to each image and generally results in a fairly soft, not
very sharply defined image. )
Any type of light can be mixed if the hot lights (incandescent)
are fitted with infrared screens to filter out the infrared rays and
leave the cold light to pass through and affect the tube in the
camera. Also special filters are often placed over the lights to