Hot shoe; Hotshoe; Hot-shoe
The hot shoe is a bracket on top of a camera. It is designed to receive the bottom part (foot) of an off-camera flash unit. The foot of the flash slides into the restraining slots either side of the hot shoe. Usually the flash has a screw or friction clamp of some kind which is applied to hold the flash unit in place on the hot shoe. The flash should be placed into the hot shoe the correct way around. Incorrect fitting may cause the unit to fail, short out or do mechanical damage to the hot shoe bracket and slider on the flash. The flash unit should slide into the hot shoe with a firm, but gently applied pressure. Any attempt to force the unit is likely to cause damage. The hot shoe bracket dimensions are compliant with the International Organization for Standardization (ISO) specification: ISO 518:2006.
When in place there are at least two electrical contacts between the camera and the flash. The first is a central contact on the flash foot which directly touches a central contact point in the hot shoe bracket on top of the camera. The contact on the flash foot is often a sprung ball-bearing contact allowing the contact to slide into place without damage. The second contact between camera and flash is the hot shoe bracket metal itself. When the flash slides into place the metal of the hot shoe bracket is pushed up against a spring contact in the slider on the side of the flash foot. These two contacts allow an electrical impulse from the camera to fire the flash.
Other contacts may be available inside the camera hot shoe bracket. These are designed to carry data which the camera uses to monitor the internal state of the flash, its performance and to change its settings. The placement of these additional contacts and their purpose is dependent on brand. If the photographer is using a flash unit that is not the same brand as the camera then in most cases the data contacts will be unused.
The central electrical contacts and the voltages used are subject to a standard specification (ISO 10330). This specification allows for 24 volts. However, in practice this flash voltage can differ considerably from under 6 volts to a possible several hundred volts in old flash models. Modern cameras are very sensitive to electrical overload. Photographers are advised to seek advice on which flash units are compatible with their camera model.
The hot shoe may be used for other accessories. These may include radio trigger transmitter to fire a remote flash, microphones for video recording, spirit level, other types of lights (like LEDs), gps units, range-finders as well as light-weight reflectors or diffusers for the pop-up flash. Accessories may or may not draw power or be activated from the camera.