The standard lantern with a single lens gives beam angles up to 22 degrees. The shape and size of beam are varied by using one of the four standard diaphragms, a special mask, an adjustable type mask, or iris diaphragm. The beam angle may be decreased to 11 degrees max., and intensity increased over three times the standard, by fitting a front with a 6-in. lens, instead of the standard tube. The lantern is then suitable for long throws. Ventilated die-cast aluminium body and lens tube assembly designed with medium prefocus lampholder for the alternative lamps listed below.
Body is hinged at the rear to give access for lamping and cleaning.
Rear part carries a 7-in. Four diaphragm masks with circular holes supplied as standard. Front of lens tube has runners for and is supplied with one metal colour frame. Stem can be unscrewed and replaced by any three-eighths inch Whitworth bolt for fixing to standard L clamps and other suspensions. Wired with 3 ft. heat-resisting tails and stoved crystalline black outside, matt black inside.