Spring 2012

Spring 2012
by ani

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I am wondering about the 5 contact points on the top of the Canon camera for the flash. The flash I am putting on this camera has only the center contact. What are the functions of all these other contacts?

Also the manual says that the camera flash must be up in order for the camera to send signals to slaves, so if I mount my x brand flash, do I have to have the camera flash up also?

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The extra contacts on the Canon hotshoe are to allow the flash to communicate with the camera, in order for the flash to read camera settings (such as the lens focal length to set the zoom factor) as well as access to the camera's light meter to perform automatic TTL (through the lens) flash metering.

To simply fire a flash in time with the camera shutter you only need two contacts. Your flash has two contacts, the centre one you refer to, and one on the side of the dovetail that makes contact with the hotshoe rails.

In the olden days the hotshoe was a simple mechanical switch that closed when the shutter mechanism moved. Nowadays it's electronically controlled. This means you should be careful when using old flashguns on camera as the voltage of the flash trigger circuit can be several hundred volts, which can damage the camera. In this case the use of a wein safesync or similar is recommended.

The camera's popup flash is only required to communicate with off-camera flashes. When using a third party flash on the camera hotshoe you should not raise the built in flash.

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Did you mean to say "...you should NOT raise the built in flash." – Dave Nelson Mar 21 '13 at 17:10
Do note, though, that some older Canon cameras never used the centre contact (the EOS Elan 7E, the 10D and the original Digital Rebel/300D among them). For those cameras, you would need a hot shoe adapter (or use the PC terminal, in the case of the 10D). And let's be thankful that Canon changed their minds about that, otherwise Canon users would be in the same sort of boat as Sony/Minolta users, except that their useless third-party flashes would appear to fit on the camera. – user2719 Mar 21 '13 at 17:43

The extra pins are used for proprietary communication between Canon camera bodies and compatible flashes (primarily Canon, but some third parties have backwards engineered the communication). It includes information about through the lens metering and also the ability to control settings on the flash from the camera body.

As far as the flash having to be up for slave flashes, that is only if you are using Canon's optical flash sync. The camera body you have is able to remote control Canon speedlites, but if you are using a hotshoe flash (the flash that goes in the groves on the top of your camera, then you do not need to use the optical sync since it is hardwired to the hotshoe.

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