Fibres

by Colin Gray

Reproduced from in focus 38 (October 1990)

I have lost count of the number of problems that have occurred with leads for underwater flashguns. "Waterproof' leads that leak. "Wet" leads that can in theory be connected and disconnected underwater have an annoying tendency to trigger themselves with any slight movement.

Sooner or later both types can fracture, repeated exposure to pressure breaking the strands of the cable one by one until there is an erratic fault either at the camera or flashgun end.

The recent interest in TTL flash is likely to amplify the problem, because of the extra wiring involved. "Splashing out" on a Motormarine II last season was, for me, initially a step backwards. I have found no real advantage in the TTL system, but it meant reverting not only to "dry" leads, which cannot be unplugged underwater, but also to only one flashgun, with the strong shadows that such a system can produce.

I do have a couple of small Ikelite flashguns, fitted with "wet" leads, that have slave sensors built-in. Now these things are smashing for your buddy to hold so that you can take pictures of your gun firing, but not very sensitive if trying to trigger them yourself.

The solution is, as usual, obvious once you see it. In our local "Aladin's cave" of odds and ends I found a length of fibre optic cable. With a bit of patience and quick setting epoxy resin, I moulded a socket at the base of the 'master", built-in, flashgun and another over the sensor of the "slave", remote, flashgun.

The result is a tiny, waterproof, incompressible "wet" lead that can be replaced very cheaply and quickly when necessary. It should even work if fracturedl The prototype cable has now formed a couple of interesting right angles, but fires the slave every time.

The initial results have been very encouraging. Phase 2 has involved installing a tiny flashgun inside my SLR housing to trigger two slaves, although there is no limit to the number that could be triggered this way.

A slight "technical hitch" occurred at this stage . . at a depth of 20 metres the picture started to wobble! Experts call these shots "split image", but it is not recommended to allow water inside the housing in order to achieve them. Anyway, it was my lucky day and the water did not penetrate the camera itself. The housing has now been rebuilt and phase 2 is working perfectly.

Phase 3 - with the appropriate electronic circuits at each end, there is no reason why even "dedicated" flashguns and cameras cannot communicate with each other down an optical fibre. We might even have a TTL system driven by one lead I

Postscript

The Sea & Sea flashgun leaked after 11 month's use, probably the cable as usual. It was returned as "beyond repair", so I have converted it into another slave, and am using the Sea & Sea built-in flashgun to fire three guns!