Manufacturer: Osram
Model: Halospot 70 50W 12V.  41990 FL BA15d 24
Application: Specialist - Directional/display lighting
Wattage: 50W
Diameter (max): 70mm
Length: 50mm
Tube Length: --
Bulb/Tube material: Quartz lamp, aluminium reflector
Colour Temperature: ?
Peak output wavelength: N/A - Broadband emission
Total light output: ?
Rated lifetime: 2000 Hours
Cap: BA15d
Operating voltage: 12V
Operating current: 4.16A
Warmup/restrike time: None
Cost (original): Unknown
Value (now): 8.44 (Compatible lamps available from BLT Direct)
Place of manufacture: Germany
Date of manufacture: Unknown - Code i768 present on lamp crown.
Current Status: Working
Notes: The market for display lighting is a hugely competitive one.  Companies are continually battling to provide brighter, more tightly controlled beams of more uniform colour, and of course higher energy efficiencies.  While this does mean that it's a lighting field where progress tends to be somewhat ahead of general lighting (hence the relatively commonplace use of compact metal halide and WhiteSON lamps), it does mean that technologies have an annoying tendency to become obsolete quickly.  These lamps are now quite rare, as compact quartz halogen lamps with external dichroic reflectors have become far cheaper alternatives - offering an added advantage of a (relatively!) cool beam.

This Osram product is a smart unit.  A complete unit consisting of a 12V quartz halogen incandescent lamp, a solid aluminium reflector, a glare shield and a BA15d bayonet cap.  All in a box, ready for service.  The complete optical system and lamp unit means that with every lamp change, a perfectly aligned beam is maintained, and a new, clean reflector is fitted.  Unfortunately, this convenience comes at a cost.  The Halospot lamps were and still are very expensive when compared with other systems using an open reflector and a replaceable lamp.  Even in bulk, I imagine these lamps probably run to 5 apiece, whereas a cheap capsule style 12V halogen lamp can be snapped up for well less than a pound.  If you're running display lights 24 hours a day, you don't need me to tell you that over a year, that's a considerable difference.

The glare shield, axial filament and specially designed reflector produce a perfect beam (though I have not yet powered this example up, as I need to track down a suitable cap, know I have one somewhere!), which is devoid of the off-axis glare common to open lamp systems.  Unfortunately, this highly concentrated beam contains not only all the light produced by the lamp, but all of the heat.  The reflector, being aluminum, reflects heat just as well as it does light.  Meaning that at anything less than long range, these lamps really are only suitable for lighting of items which will not be bothered by (considerable) heat.  This is a problem not encountered by lamps using dichroic reflector, where the vast majority of the heat is dissipated out to the rear of the lamp.

Once these lamps were highly popular for display lighting, but since then, dichroic reflectors and cheap halogen lamps have come and stolen its place, which is in turn being slowly advanced on by the ever more accessible compact HID formats.  Now however, this one forms an interesting part of my collection.

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Lamp added to the Virtual Display Shelf on Thursday 28th August 2006 at 20:21.

References: None.  I'd have loved a datasheet if I could have found one though!

Acknowledgements: Many thanks to the website user who kindly donated this lamp for display!