Introduction

The Source Four is manufactured by ETC, Backstage own several different versions of source 4's this guide covers the source 4 fixed. The source 4 fixed is a profile light, it can be found in the backstage cupboard in four different beam angles: 19,26, 36 and 50 degrees, but it is also available in 5, 10, 14 and 70, 90 degree beam angles. The lens tubes are separate and interchangable. It uses a 575 watt quartz-halogen bulb, but the optics of this lamp make the light output equal to or exceeding that of a standard 1kW lamp. The newer Source 4's can be lamped at 750 watts and have a slightly diffent heatsink to deal with the extra heat. ETC say that you can't just lamp your 575's up to 750's due to heat issues.

Focussing

The light provided by the lamp is reflected by a parabolic mirror through a gate and a lens. The lamp itself can be finely adjusted by means of a screwthread on the back to position it exactly at the focal point of the reflector. The gate has shutters that can be used to shape the beam so that it can be made to have flat edges where desired ans also facilitates the insertion of a gobo. Finally, the lens unit at the front can be moved closer to or further away from the gate which focusses the beam; this allows the edges of the beam to be softened or hardened as required.

Lamps

A Backstage Source 4 fixed should be lamped with a HPL 575 (575W). The lights that have a plastic backend with a handle can also be lamped with a HPL 750 (750W).

Things you need to look out for

The back of the Source Four gets very hot, very quickly. It is now standard for Source 4's to have a shield on the back to protect focussers, however, not all of BTS's source 4's have one. When focussing, avoid having the lamp lit for long periods of time and if possible, focus at 50% to keep the lamp cooler for longer. The gate and shutters stay much cooler, though care should still be taken.

Further information

Source Four User Manual (326k, PDF)

Credits:
The Backstage Lighting Guide was written by Chris Dickson and is © BTS 2000. Updates made by Colin Paxton © BTS 2008
No reproduction in whole or in part in any means whatsoever is permitted without written consent.