On the top of Canon cameras is a Hot Shoe that sends signals to an attached flash.
The advancement of camera and external flash technology now has cameras and external flashes communicating with each other. The data that flow from the camera to the flash and back is designed so that the camera and flash work together to produce the best possible picture. At the top of Canon cameras is the hot shoe. This device has four small round contacts and one larger one in a "U" shaped configuration. It is through the hotshot that these data are transferred.
Large Round Contact
The larger round contact is the contact which ultimately sends the signal for the flash to fire. A small electrical charge travels through this contact to the corresponding contact on the flash. If you look at non-automatic flash units, you will see they only have one pin in the center.
Four Small Round Contacts
These contacts are used for the transmission of exposure information between the camera and the external flash. While Canon has not released exactly what each contact does, we know the larger contact sends the flash signal, leaving the smaller ones for data transfer.
Locking Pin
There is one additional pin that is held in a recessed position until the external flash is connected and secured in place on the camera. This pin usually is in front of the larger contact and is exposed when the locking ring on the external flash is tightened.
Tags: external flash, camera external, camera external flash, camera flash, Canon cameras
