The EG&G Microflash was manufactured (I believe) from the early 60′s through to the early 80′s. Designed by Harold “Doc” Edgerton and his team, it was the original commercially available high speed flash unit. It cost thousands of dollars new, and boasted a 0.5 microsecond flash duration. In fact, the flash was an air-gap spark, about an inch and a quarter long, guided through a notch in a quartz tube. The Microflash is sufficiently fast to stop bullets and other supersonic projectiles, though the flash-to-subject distance had to be quite short, as there wasn’t much illumination.
The image above shows the flash head of the EG&G Microflash 549
The anode voltage is around 18kV, with a couple of pulse caps storing the energy. The system comprises of a power supply and separate flash head – the 18kV being generated locally in the flash head unit. These systems are notoriously temperamental, but the images they have created over the years are legendary.
The front panel of the power supply unit to the EG&G Microflash
Notice that the power supply has a number of controls – you can program in a delay between the Microflash receiving a trigger signal, and actually firing the flash. The two pin remote input socket is for any triggering sensor, and EG&G provided a microphone as part of the system. The sensitivity control adjusts the gain of the microphone amplification, and could be set anywhere between a quiet click of the fingers to a gunshot. A separate BNC connector for an external synch is also available.
The rear panel of the EG&G Microflash 549 High Speed Flash Power Supply Unit
Here we can see the pop-off cover for an optical slave trigger, along with the AC input, and cords to the flash head unit. You can also daisychain the head to the power supply to provide AC mains power to the head. Alternatively, it could be plugged directly into an AC mains socket. The grey lead connects to a multi-pin Jones socket and provides an approximately 200V trigger pulse to the flash head. The black lead is the AC mains input. These can be seen in the image above this one.
This is the rear panel of the flash head of the EG&G Microflash 549
Here we see the Jones socket that accepts the plug from the power supply that produces the triggering pulse. The black lead is the AC mains lead that can plug into either the power supply unit or another AC mains socket. This unit is quite light, and has an aluminium plate underneath with a threaded tripod socket for mounting.
It is possible to connect two flash heads to a single trigger supply unit, by creating a spliced cable with Jones connectors, and I have done this. I own two flash heads, but only one trigger supply. It is very difficult to synch the two flash heads perfectly – there can be as much as 40% jitter over the width of the output light pulse, but unless you are photographing something REALLY fast, this is not an issue, and you will not see any double exposures. I love working with these units, but I am very selective about when I use them, as they have a very finite lifetime, and they haven’t been made for around 30 years. Oh, and they fire with a very loud (and satisfying!) BANG!!
My good friend, and photographic pioneer extraordinaire Andrew (Andy!) Davidhazy of Rochester Institute of Technology (RIT) has kindly posted the entire operating manual (including circuit schematics) for the EG&G Microflash at his RIT website. The manual is available as a PDF here.
In fact, if you are at all interested in photography, his website is a goldmine of information – from deep theory, to fun and simple experiments. You will learn a lot, I promise. His website is here.
Fortunately in the last few years, there is a new unit that has been developed to supercede the EG&G Microflash. It is produced by Prism Science Works, and is called the SPOT Flash. It improves upon the Microflash in that it is a single integrated unit, has a Fresnel lens and is modestly priced. You can read more about it here. The design of the Microflash tube/reflector combination does not provide very even illumination, and one has to be careful to avoid hotspots in the resultant images. The new SPOT flash eliminates this problem with the use of a Fresnel lens, and I have heard it produces a very uniform distribution of light over the illumination area.