Theatre Design & Technology - May 1968 - 21

500,000'r-----.---~.....- - - , _ _ - - - _ _ ,

1000 WATT
TUNGSTEN - HALOGEN
150 HOUR LIFE
3200· K
AXIAL MOUNTING
400,OOOI------l--I-~---1-\-'\--+------i

1000 WATT
TUNGSTEN-HALOGEN
HOUR LIFE
3200· K
TRANSVERSE MOUNTING

300,000 1-------4---,I--+-+-+----1f-+-----::==i 150

I
I
J
J

I
".

l'

200,000

,,

r--

1

,

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t
t

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,1

beam appearances. In Fig. 5b, note that the filament
"images" are quite obvious even though they typically represent variations in illumination of about 20 per cent. This is
due to the fact that they are clearly delineated. Although it
is not obvious photographically, the "uniform center" in
Fig. 5c as chosen by most observers covers a range of
about 3: 1 in illumination. This large variation at the center of the beam is generally "recognized" as constant due
to the gradual change involved.

Figure 5. light patterns of the beam projector shown in Fig. 4.
Note that these are not to the same scale so that maximum detail
will show. (a) Standard incandescent lamp. (b) Axial tungstenhalogen lamp. (c) Transverse tungsten-halogen lamp.

1000 WATT
STANDARD
INCANDESCENT
200 HOURS LIFE

a

ANGLE FROM FIXTURE CENTERLINE

Figure 4. Intensity distributions of a 16 inch beam projector using
three different lamps. The standard incandescent lamp, the axial
tungsten-halogen lamp, and the transverse tungsten-halogen lamp
produce respectively the following characteristics (beam angle, field
angle, beam efficiency, field efficiency): (7", 13 ';", 1 1 %, 19%1,
(7';", 12Y,', 22%, 31Y,%). and (4', 10', 6%, 12Y,%).

Figure 4 compares the intensity distributions of a standard
16 inch diameter beam projector using various sources. Due
to the compactness and higher brightness of the filament,
the tungsten-halogen lamps produce a significantly greater.
intensity than the standard incandescent lamp. The axially
mounted tungsten-halogen lamp gives the same nominal
beam size as the standard incandescent lamp with about
twice the axial intensity. The transverse tungsten-halogen lamp
yields the same intensity increase, but the beam is narrower.
As would be expected, the efficiency increases with the
axial lamp by a factor of 1 V2 to 2 due to the intensity increase. The narrower beam of the transverse lamp forces
the efficiency down; this is the price paid for a very narrow
beam. The small envelope of the tungsten-halogen lamp permits use of a smaller lamp shield used to eliminate the
direct lamp light; consequently, less of the paraboloidal reflector is hidden.

b

Figure 5 shows the light patterns of these three lamps in
the same instrument when projected on a wall. The standard
lamp produces the familiar mottled pattern. The axial filament produces a significantly nonuniform pattern. The central hot spot and filament images are typical of axial filament
performance ohen found in paraboloids. These can be corrected by a design modification of the instrument. Diffusion
would smooth the beam, but this works against the objective
of a beam projector. The transverse lamp functions quite
well for a direct interchange with a standard incandescent
lamp. Figure 5 is reasonably representative of the visual

lusm

May 1008

c

21



Table of Contents for the Digital Edition of Theatre Design & Technology - May 1968

Contents
Theatre Design & Technology - May 1968 - 1
Theatre Design & Technology - May 1968 - 2
Theatre Design & Technology - May 1968 - 3
Theatre Design & Technology - May 1968 - Contents
Theatre Design & Technology - May 1968 - 5
Theatre Design & Technology - May 1968 - 6
Theatre Design & Technology - May 1968 - 7
Theatre Design & Technology - May 1968 - 8
Theatre Design & Technology - May 1968 - 9
Theatre Design & Technology - May 1968 - 10
Theatre Design & Technology - May 1968 - 11
Theatre Design & Technology - May 1968 - 12
Theatre Design & Technology - May 1968 - 13
Theatre Design & Technology - May 1968 - 14
Theatre Design & Technology - May 1968 - 15
Theatre Design & Technology - May 1968 - 16
Theatre Design & Technology - May 1968 - 17
Theatre Design & Technology - May 1968 - 18
Theatre Design & Technology - May 1968 - 19
Theatre Design & Technology - May 1968 - 20
Theatre Design & Technology - May 1968 - 21
Theatre Design & Technology - May 1968 - 22
Theatre Design & Technology - May 1968 - 23
Theatre Design & Technology - May 1968 - 24
Theatre Design & Technology - May 1968 - 25
Theatre Design & Technology - May 1968 - 26
Theatre Design & Technology - May 1968 - 27
Theatre Design & Technology - May 1968 - 28
Theatre Design & Technology - May 1968 - 29
Theatre Design & Technology - May 1968 - 30
Theatre Design & Technology - May 1968 - 31
Theatre Design & Technology - May 1968 - 32
Theatre Design & Technology - May 1968 - 33
Theatre Design & Technology - May 1968 - 34
Theatre Design & Technology - May 1968 - 35
Theatre Design & Technology - May 1968 - 36
Theatre Design & Technology - May 1968 - 37
Theatre Design & Technology - May 1968 - 38
Theatre Design & Technology - May 1968 - 39
Theatre Design & Technology - May 1968 - 40
Theatre Design & Technology - May 1968 - 41
Theatre Design & Technology - May 1968 - 42
Theatre Design & Technology - May 1968 - 43
Theatre Design & Technology - May 1968 - 44
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