The Use of Non dedicated Flash on Canon EOS Camera

Published: 25th November 2008
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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 Camera's 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 camera's 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

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