The flash circuitry inside a disposable camera may contain
dangereously high voltages even when there is no battery in the
camera.
If you don't have experience with this kind of projects
or don't know what you are doing, for your own safety, don't attempt
to follow these instructions.
It is easy to make an underwater slave flash out of the flash unit
of a disposable camera (or for that matter any flash), a slave flash trigger
from a photo store and the shell of an underwater light.
Remove the circuit board from the camera and connect the slave
trigger to electronically close the two long contacts on the left hand
side of the board. To get more coverage for the trigger, a
transparent casing would be ideal.
One final thing you willl need: a flash reflector. The idea is to
block the light from the internal flash from illuminating the subject
(the internal flash causes the backscatter) and reflect the light upwards
so that the slave flash is triggered. A piece of e.g. aluminum
twisted into an interesting shape works.
In my experience the unit is excellent for macro work in low
visibility. Holding the flash above the Aquashot at about a
forty-five degree angle to the optical axis prevents backscatter. At
such a short distance the flash is so powerful, that 100 speed film
provides correct exposure. If you are using a standard disposable with
400 speed film, the bottom of a white 16oz sour cream container works
nicely as a diffuser to cut down the amount of light.
A piece of black plastic tied to the top horizontal bars of the
macro framer is useful as a shade to prevent the light from the flash
from illuminating the water between the lens and the subject.
