The Use of Non dedicated Flash on Canon EOS Camera
The Use of Non dedicated Flash on Canon EOS Camera

The Use of Non dedicated Flash on Canon EOS Camera

If you wish to use a generic non-dedicated flash unit on the
Canon EOS camera, you will first need to check the
triggering voltage of the flash unit. The Canon Speedlite
flash units triggering circuits is not more than 6 volts.
Furthermore, the Canon EOS 1, A2/A2E, 10s, 630; Elan, RT and
Rebel also operate with 6 volts as the maximum voltage going
through their triggering circuits. As such, you must make
sure the generic flash unit also uses no more than 6 volts
for their trigger.

Any trigger circuits which requires more than 6 volts could
possibly damage the X-Sync contact of the camera, the
shutter units or connecting wire. Damage might not be
immediate and may result over a period of time. Furthermore
the high voltage passing through the Camera connecting wire
might also generate electro magnetic "noise" resulting in
unwanted adverse effects on the camera. Errors can occur
with metering, shutter speed, aperture size etc depending on
the camera models and which part of the circuit layout is

Testing the voltages of the flash triggering circuit is a
simple task. Just use a voltmeter which is available at any
Radio Shack stores. Connect the positive lead to the
positive point of Sync Cord. The Negative lead should be
connected to the ground of the Sync cord. With shoe mounted
flash, just connect the positive lead to the center point of
the mount. The negative lead has to be connected to the
grounding point of the camera located at the side of the
lock nut. Voltmeters have different setting which you can
use. If you are unaware of the voltage of the Flash unit,
just use the highest setting on the voltmeter than work your
way downwards.

You can actually fire a Studio Flash unit safely without a
Sync cord. To do so, just use a Speedlite 420EZ or 430EZ at
1/32 power setting under manual flash mode. Make sure the
optical slave trigger is turned on before firing. What you
are actually doing is utilizing the bounce features of the
Speedlite 420EZ or 430EZ to divert the flash light to the
optical slave trigger. On the other hand, you can use slave
triggers which are linked by radio signals to fire the
Studio flash. These radio transmitters and receivers, which
are connected to the Cameras PC contact and the Flash power
packs, are manufactured by companies like Lindahl and
Quantum Instruments.

If the EOS camera is not firing the Studio flash, check the

1. Ensure that the PC socket adapter does not come with
metal shoes. Metal shoes will cause a "short" in the
triggering circuit. To avoid this problem, use a Canon PC
socket adapter made from plastic.

2. Make sure that the flash units polarities are in the
correct order with the X-Sync of the camera contact point.
The reversed polarities are normally caused by a diode which
is coupled to the cameras X-Sync contact for the protection
of the camera internal flash. To correct this problem,
simply reverse the polarity of the Sync Cord.

3. If after having tired these two suggested solution and
the Flash still wont fire, then just adopt the method
described above to fire the Flash without the use of the
Sync cord.

Tim Harris is a canon camera enthusiast. For tips on
choosing and buying cameras, do check out href="">Canon OS Camera
website. Camera 40D
Digital Rebel XTI 3D