Tuesday, November 18, 2008

Canon EOS Camera Generic Non dedicated Flash Units

By Tim Harris

Prior to using a Generic Non dedicated flash on the Canon EOS camera, you have to check the trigger voltage of the Flash. The Canon lines of Speedlite flashes do not use more than 6 volts with their trigger circuits. The Canon EOS 1, A2/A2E, 10s, 630, Elan, RT and Rebel operate with 6 volts as the maximum voltage going through their triggering circuits. Therefore you have to make sure that the generic flashes also adhere with this limitation.

Those triggers which use more than 6 volts can damage the electrical circuitry of the camera. The connecting wires, the X-Sync contact point and the shutters are most prone to damages. The damage might not be obvious but will happen gradually over time. Beside from the likelihood of circuitry damages, electro magnetic noises generated by the high voltages will cause interference with the Camera operation. The metering system, aperture settings and shutter speed are just some of the possible effects of electro-magnetic noise on the circuit of the camera. Which function will be affected will depend ultimately on the circuits which is interfered with by the electromagnetic noise.

To test a Flash trigger circuit voltage level, you just need a simple voltmeter. This can be purchased at any Radio Shack stores. Just connect the positive lead to the positive of the PC contact of the sync cord and the negative lead to the ground of the PC sync cord. For those Hot Shoe mounted flash units, the positive lead should be connected to the middle of the shoe mount while the negative should be connected to the ground contact on the side of the lock nut. All Multimeters or Voltmeters have different setting for you to test the DC voltages. If you do not know the voltage, then it is best to start testing in the high range downwards.

There is also a way which you can fire a flash without a Sync cord. To do this, you need the Speedlite 420EZ or 430EZ set at 1/32 power under the manual flash mode. Make certain that the optical slave trigger of the flash are turned on. In essence, you are making use of the bounce feature of the flash to redirect the flash light to the optical slave trigger. You can also use wireless radio transmitters and receivers which are connected to the PC contact and Flash Power pack to fire the Studio flash. These wireless gadgets are available from companies like Lindahl and Quantum Instruments.

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

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) Ensure that the Polarities of the Flash Units are correct with the camera X-Sync contact. This is usually caused by a diode connected to the Camera's X-Sync contact to protect the camera internal flash. The solution is to reverse the polarity of the sync cord.

3. If the two troubleshooting tips do not work, just use the method described above on how to fire a studio flash safely. - 15437

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