GE MARC-350/16T "EZT" Metal Halide Projector

The GE family of "Marc" and "Gemini" lamps are short arc metal halide products, which were developed during the 1970's specifically for the projection of 16mm films. They are characterised by the very short arc gap, made possible by operating the lamp at very much higher pressures than would normally be encountered - typically in excess of 50 atmospheres. All types are intended for DC operation, hence the asymmetric appearance of the arc tube to account for the different electrode sizes.

Despite being made from quartz and with no front glass, a unique feature of these lamps is that they generate no UV output. This is owing to the high concentration of indium bromide in the arc tube, a useful feature of indium being that its vapour absorbs radiations below about 380nm. Consequently any UV generated by the discharge is absorbed by the indium vapour in the arc tube, and is unable to exit the lamp.

The arc tube is mounted axially within a dichroic coated reflector. This delivers a cool beam of light forward, while allowing some 60% of the heat to escape out the rear of the lamp. This particular lamp has a reflector designed by Emmett Wiley and Robert Downing, and features a series of asymmetrically shaped radial bands extending from the apex to the open rim. Their purpose is to produce a substantially rectangular shaped beam for more uniform illumination of the film gate.

Electrical connection is by means of a special 2-pin plug, asymmetrically designed to ensure that the correct arc tube polarity is maintained.
Manufacturer: General Electric Co. of U.S.A.
Lamp Power: 350 Watts
Lamp Current:
Lamp Voltage: 45 Volts (DC Only)
Cap: Special 2-pin plug
Bulb Finish: Dichroic Mirror
Bulb Type: PAR-76 PAR-24 (in eighths/inch)
Overall Length:
Working Distance: 52 mm
Electrodes: Solid tungsten
Atmosphere: Argon
Luminous Flux:
Luminous Efficacy:
Colour Temperature & CRI: CCT: 5000K CRI:
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Beam Horizontal
Rated Life: 50 hours (based on one hour's use per start)
Factory: Bellevue, OH U.S.A.
Date of Manufacture: April 1984 Date Code: D052
Original / Present Value: 150.13 (1991) 194.87 (2001)
References: 1) GE Lamp Catalogue, USA, 1989, p.111
2) GE-Tungsram UK Price List, 1991