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It says on Camerapedia that PC Terminal and Hot Shoe are both types of flash sync connections. If that's so, then what are their differences and primary uses?

I'm confused about it because I understand that cameras that do not have PC terminal require a separate accessory which is mounted to the hot shoe. That doesn't make sense to me, because if I can mount my Speedlite to the hot shoe, why would I need the PC terminal?

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The main purpose of PC connections is to fire, via a wired connection, studio flash units not mounted directly to the camera. The only signal a PC connection carries is that the shutter has opened and the flash should fire. It is not capable of carrying any other data. As the capabilities of wireless triggering methods have increased, wired connections of any kind between camera and external flash units not mounted on the camera are waning in popularity. Many newer camera models don't even include a PC connection in the design. If a photographer needs to signal external flash units via PC connection, then an adapter attached to the camera's hot shoe can accomplish this.

The hot shoes of most current cameras, though, are capable of communicating much more data beyond a single triggering signal to a compatible flash. Canon's E-TTL system, Nikon's i-TTL system, as well as the systems of other manufacturers use multiple contacts on the hot shoe to communicate in both directions between the camera and flash unit. This allows things such as automatic flash metering, power adjustment, second curtain sync, and controlling multiple flashes via optical pulses between the hot shoe mounted 'master' flash and several external 'slave' flash units.

If a photographer desires a wired TTL connection off camera, hot shoe cables that include wires for all of the connections between the hot shoe and speedlight are available. Wireless triggers can also attach to a hot shoe. Some wireless units only transmit a single signal, like the old PC connection, that tells the flash to fire. Others allow the full communication between a camera and flash that enable the same functionality as if the flash where mounted directly on the camera's hot shoe.

Which of these connections will work best for you depends on what flash units you have, what camera model you are using, what amount of communication you need between the camera and flash, and how much your budget is.

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The PC terminal is for operating your flash off-camera.

When a flash is in the hot shoe you are stuck with it right on top of the camera, when you us a PC cord the position of the flash is only limited by the length of your cable (or the range of your wireless triggering device).

Some more things to know about the PC terminal:

  • The PC terminal does not support TTL, you can only use it with the flash in manual mode (or, for flashes that support this, the older less useful flash auto mode that uses a light meter in the flash itself)

  • The PC connector isn't very good mechanically, newer devices tend to replace the PC terminal with (or add to it) a audio headphone-style jack

  • There are cables and remote triggers that connect directly to the hotshoe, A PC connector or a hotshoe-PC adapter isn't always required for off-camera flash

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The pc cord when plugged in isolates the hot shoe center contact. If you are using flash remote triggers this is required to protect the trigger from the high voltage from the flash gun. Eg old cobra 720Af gun gives 240 volts out at its base which will destroy a dslr cam or electronic trigger. This means you can use the RF trigger with high volts old guns like viv 283 etcbut still put the gun in the trigger shoe.I think this clears up a number of points along the way cheers john m

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