VHSF

The Very High Speed Flash System (VHSF)

This is a custom system I designed for a client a few years ago, and finally got around to replicating for myself. It comprises of a main power supply, with remote heads. The heads are attached to the supply via 10ft cables, also custom designed, with high-voltage and high-current connectors. The flash duration is around 20 microseconds, or 1/50000^th of a second, and I can shoot hummingbirds at f20, ISO100 with the heads placed a few feet from the subject.

VHSF Specs:

Operating Voltage: 3000V or 3kV

Flash Duration: ~20 microseconds*

Energy: ~45 joules, or wattseconds

Power Source: 120V AC

Recycle Time: ~1.5 seconds

# of Flash Heads: Up to 4

Flash Head Reflector: ~7” diameter, diffused lens, housed in polycarbonate enclosure

Flash Tubes: Color corrected to 5250 degrees Kelvin

Power Supply: 4 output connectors, manual trigger, synch input, polycarbonate enclosure

Cables: MIL-Spec connectors, rated at over 10kV and 1000 amperes. (Yes, that is 1000)

Weight: Heavy.

This design is truly unique, and the flash heads emit the softest light I have ever seen from a High Speed Flash (HSF) unit. It is perfect for photographing hummingbirds around my house, but of course, using it in the field is not possible due to it being AC mains powered.

The main components in this system are:

Flashtube – operating voltage of 3kV

Energy Capacitor – 10uF (microfarads), at 3kV (at least) working DC voltage (WVDC)

This provides output energy of around 45 joules, and a flash duration of around 20uS.

There are numerous parasitic factors that are all detrimental to the flash duration, such as the resistance (and inductance) of the cables, energy capacitor etc. so it is a little bit of black art, as well as science that helps us arrive at a final design.

* The flash duration of this system is adjustable, though not very easily. The capacitor used in this system was a custom designed component that is actually a compound cap – it has terminals that can be connected to provide anything from 6uF to 25uF, depending on the duration required. I have found that 20uS duration is sufficient to stop most action, and still produce a very significant output power.