Theatre Design & Technology - May 1968 - 24

CONCLUSION: Tungsten-halogen lamps provide a method of
improving the performance of luminaires common to the
theatre, television and film lighting industries. It is essential,
however, to understand the required performance characteristics and the methods used to evaluage these characteristics. The significant ones are the lamp properties, the optical performance and the maintenance factors. An examination of these characteristics when tungsten-halogen lamps
are utilized in existing luminaires indicates that some benefits are obtained. Greater improvements, however, are obtained when luminaires of new design take full advantage of

APERTURE

the tungsten-halogen lamp's properties.
LENSES

20,000'r----,--------,r---JL--.~...,___-__.--~~-~r____.---'2000WATT

Figure 10. Schematic diagram of the unit in Fig. 9. The source is
a 500 watt, 150 hour, 3200·K color temperature tungsten-halogen
lamp. The lens and shutter system is similar to a 6 inch reflector
spotlight; the lenses are 6" x 9" plano-convex. The efficiency is
somewhat higher than for conventional units, and the central intensity can be adjusted from 1 '12 to 2 times that of the conventional
unit with a 2 to 3 times improvement in beam uniformity.

TUNGSTEN· HALOGEN
3200° K

15,000

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10,000

There are several methods of using a tungsten-halogen lamp
in these instruments. If the lamp is directly substituted in a
conventional instrument (transverse orientation), the performance does not increase significantly; however, the maintenance gains of the tungsten-halogen lamp will be realized.
The reflector will be less effective due to the compact filament. A new luminaire design was constructed to illustrate
the potential of new design concepts. Figure 13 shows
this device, and Fig. 14 illustrates the system schematically.
The small envelope permits a small reflector to subtend a
large solid angle about the source. This reflector is nearly
elliptical in section. The light is brought to a focus ahead of
the lamp. This concentration of light serves as a source for
the lens. Since more of the lamp lumens are utilized than
for the transverse orientation in a conventional instrument,
the efficiency gain is more significant. The area of light concentration ahead of the lamp has a larger size than the
actual filament (a characteristic of the elliptic form); this can
increase the intensity.1 The reflector departs from a true
ellipsoid to produce a more uniform beam pattern.

1500 WATT PS 52
3200 0 K

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600

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ANGLE FROM FIXTURE CENTERlINE

Figure 12. Intensity distributions for an 8 inch, 1000 watt conventional Fresnel lens spotlight showing the effects of the spherical
reflector.

60·

400

Figure 11. Intensity distributions of an 18 inch scoop using three
different lamps. The standard lamp, the 1000 watt tungsten-halogen
lamp, and the 2000 watt tungsten-halogen lamp produce respectively the following characteristics (beam angle, field angle, beam efficiency. field efficiency): (89·, 115·, 52%. 60%). (88·,111·, 65%,
75%). and (85·, 116·, 58%, 67'12).

Figure 15 illustrates the beam and field efficiencies as functions of the beam and field angles respectively and compares
them to the values for typical conventional instruments.
Figure 16 shows tile intensity distribution of one intermediate setting for the instrument of Fig. 13 in comparison
to a similar size conventional instrument. Since the beams
are not of the same shape, equal settings are not possible.
Settings of the conventional instrument are chosen to match
the field angle of the demonstration tungsten-halogen instrument. For equal field angles the two instruments have
the same maximum intensities. When the beam angles are
matched, the conventional instrument has a higher center
beam intensity. However, the fact that the tungsten-halogen
demonstration unit is 50 per cent of the wattage and has
150 per cent of the life of the conventional instrument will
more than equalize this difference. The instrument of Fig.
13 will vary from a flood setting of 36° beam angle, 59°
field angle to a spot setting of 8° beam angle, 1 1 ° field
angle. The reflector and lens design of this type of system
can be varied to produce different intensity distributions and
different adjustable ranges.

200

ANGLE FROM FIXTURE CENTERLINE

THEATRE DESIGN AND TECHNOLOGY

20·

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