Using a flash with the Triggertrap

July 2013

Another way to catch fast moving objects is to darken the room, set the camera to BULB, then trigger a flash at the appropriate moment. The Triggertrap can also be used to trigger a flash... if your flash is a modern low-voltage flash. Older flashes designed for mechanical cameras can show extraordinarily high voltages across their hot shoe terminal. The Strobe Trigger Voltages website explains this in detail.

In brief, before using an older flash you must check the voltage. You do this as follows:

  1. Power up the flash and let it charge up.
  2. Use a high-impedance voltmeter (like a digital meter) and measure the voltage across the two hot shoe connectors.
  3. If you measure more than six volts, don't use it with a digital camera or the Triggertrap!
My "Sunpak Digital Flash" passed the test. If you find your flash has a high voltage, I suggest you go buy a new one.

The otherwise excellent website might lead you to think the Vivitar 283 is usable, don't try it!. It just so happens the HiViz trigger devices are rated for 400 volts. Your camera and Triggertrap are not!

Using an older flash

If you insist on using an older flash, there several web resources that will guide you in modifying it for low-voltage use.

Bear in mind when taking a flash apart that there will still be high voltage present on the big capacitor, even with the batteries removed and the flash flashed!

Bursting balloons again

I thought perhaps using a flash might improve my photos of bursting balloons. At least this would eliminate the delay due to shutter lag, since the shutter would already be open, I even tried putting some water in a balloon to prolong the bursting action. As you can see below, I still didn't get the shot I wanted.

Camera on BULB and triggering the flash.

...and with a little water in the balloon.

Triggertrap brand flash adapter (TT-FA1)

Just after I completed the balloon experiment Triggertrap announced a flash adapter of their own, the TT-FA1. This is a small cube with connectors on four sides:
  1. A hot shoe
  2. A second hot shoe
  3. A 1/8" monophonic socket
  4. A threaded 1/4"x20 socket for tripod attachment.
Click either image to enlarge.

Inside the flash adapter there are no components, simply the two hot shoes wired to the socket. A 1m. long 3/32" to 1/8" stereo cable is included to connect it to the mobile dongle. The price is $29, which seems high for what it is.