Mazda FA.5 Xenon Photoflash
Created in 1951, the Mazda FA.5 lamp was the first commercial light source capable of matching the luminance of the sun.  Its arc operates between solid tungsten electrodes in an atmosphere of pure xenon containing in a tubular hard glass envelope.  It is designed to be operated continuously from the mains with an inductive ballast, or as a powerful electronic flash tube on a 2000V supply.

Under continuous operating conditions its spectral characteristics are those of a normal xenon arc, but under high-intensity flash conditions there is a slight shift towards the blue end of the spectrum, so that the colour approximates to that of North-sky daylight.  Colour rendering is excellent.  Full light output is reached almost immediately and dimming can be effected with negligible variation in the colour of the light.

As a flash tube, the unusually small arc and high intensity makes it especially suitable for use with precision optical systems.  Setting up and focussing can be facilitated by continuous operation of the tube.  Its excellent performance in optical systems made this lamp the first light source that enabled retinal photographs to be taken inside the human eye, and it made a huge contribution to medical knowledge in this area.

As a continuous burning lamp, its main advantage was its low cost and simplicity compared with quartz high pressure xenon lamps.  A standard hand-held tesla coil was used to ignite the arc which ran in series with five 400W mercury lamp ballasts.  In continuous burning it had to be run vertically with the electrode having the heat shield disc above
Manufacturer: Thorn Lighting Ltd.  (Lamp Ref. 97-2005)
Lamp Power: Continuous : 230 Watts Pulsed : 150 Joules
Lamp Current: Continuous : 18.5 Amps  Pulsed : (75mF capacitor)
Lamp Voltage: Continuous : 13.5 Volts Pulsed : 2kV (12kV trigger)
Cap: 3x S9
Bulb Finish: Clear
Bulb Type: T-32 with 5.0 mm arc gap
Overall Length: 148 ± 4mm
Light Centre Length: 74 ± 2mm
Electrodes: Solid tungsten
Atmosphere: Pure Xenon
Luminous Flux: Continuous : 2750 lm  Pulsed : 200 Megalumens
Brightness & MHCP: Arc centre : 2,000 stilbs MHCP : 300 cd
Luminous Efficacy: Continuous : 12 lm/W  Pulsed : N/A
Flash Duration: 1/10 Peak : 250msec  1/2 Peak : 65msec
Rated Life: Continuous : 500 hrs  Pulsed : 10 million flashes
Factory: Leicester, England
Date of Manufacture: October 1973
Original / Present Value: £18 12s 6d (1969) £185.41 (2001)