As an accessory shoe (English Cold shoe) or hot shoe (german hot shoe ) is defined as a device to cameras and camcorders, the accessories such as external flash units, lamps, viewfinder, rangefinder or water balances can be infected by a special base or foot.
Originally equipped with no electrical functions, the standard center contact hot shoe allows the simultaneous firing of the flash ( flash sync ) with the shutter release of the camera. This simple contact center basically works with the X-sync and was standardized in ISO 518.
Many manufacturers, especially of camera systems, have introduced more contacts in the hot shoe, which is used to control special functions or enhanced communication between camera and flash (for example on message or TTL flash, AF assist beam, transmission of exposure data ). On such cameras and the flash units is mostly without any special functions possible, it should be noted that older flash units use a Hochspannungszündkreis with sometimes up to several hundred volts (typically up to 400 V), which in modern cameras to damage to the electronics may cause. Before connection of such a flash to a modern, electronically controlled analog or digital camera is now set to check to ensure that the combination is electrically compatible. In general, the firing circuit of the flash may be for only a few volts ( typically no more than about 5 V).
It is also important to note that the extensions of different manufacturers are compatible with each other only in exceptional cases (eg the Leica flash system of the "R " case series largely compatible with the Minolta TTL direct flash system and also within the AF SLR group Minolta, Konica Minolta and Sony with the utmost port and protocol compatibility ); only flash when connecting unmatched foreign Flashes then ignited by the center contact ( through connection to ground ), more extensive, controlled by the camera's automatic functions are not available in this case, but available.
On the accessory shoe and other accessories can be connected as a remote shutter release; use such devices, such as viewfinder, levels, etc., but the shoe just as an assembly point and communicate with the camera via cable connections to the remote release socket.
There are also some vendor-specific holders for flash units that are already purely mechanically not compatible with the standard design.
Minolta introduced in 1988 with the "i" Housing Series AF SLR mechanically a completely different design, a hot shoe, which should allow for an easier, faster and more secure mounting and dismounting and ensure better centering. The electrical signals were compatible, and there are hot shoe adapter, which with conventional ISO shoe allow the connection of accessories to new housing and vice versa. As part of the definition of the new hot shoe was also provided mitzuversorgen plugged accessories special hot shoe contacts from the camera battery, but this has been actually realized in only one case and two small flash units. The sometimes called " reverse hot shoe " called hot shoe was taken over in 2003 by Konica Minolta and 2006 by Sony for the Alpha system. Since the end of 2012 Sony re-used a mechanically compatible to the standard ISO hot shoe.
For camcorders accessory shoe can accommodate, for example, an external microphone or a video light. However, please note that there are several types, for example, connects the intelligent accessory shoe, the electronic devices (microphone, light) with the camera, or the passive accessory shoe, which produces no electrical connection to the camera and only the attachment is used. Examples of such accessories shoes are the " intelligent accessory shoe " with 8 contacts and its successor, the "accessory interface shoe" with 16 contacts, both from Sony. As part of the NEX system, Sony has introduced in 2010 an additional proprietary accessory shoe ("S " ) with 14 contacts, which also leads to the power supply and signals for a stereo microphone next to the flash signals.