Hot shoe
Encyclopedia
A hot shoe is a mounting point on the top of a camera
to attach a flash unit
.
. Normally the metal of the shoe and the metal of the contact are electrically isolated from each other. To fire the flash, these two pieces are shorted together. The flash unit sets up a circuit between shoe and contact—when it is completed by the camera, the flash fires.
In addition to the central contact point, many cameras have additional metal contacts within the "U" of the hot shoe. These are proprietary connectors that allow for more communication between the camera and a "dedicated flash". A dedicated flash can communicate information about its power rating to the camera, set camera settings automatically, transmit color temperature data about the emitted light, and can be commanded to light a focus-assist light or fire a lower-powered pre-flash for focus-assist, metering assist or red-eye effect
reduction.
The physical dimensions of the "standard hot shoe" are defined by the International Organization for Standardization
ISO 518:2006.
The ISO 10330 specification allows for a trigger voltage of 24 volts, some manufacturers, particularly Canon, ask for no more than 6 volts. Some older flashes may have a high voltage, sometimes in the hundreds of volts. .
It is possible to connect a high voltage triggering flash with a camera which can only tolerate 6 volts, through the use of an adaptor which isolates the two units. Also many radio triggers, e.g. PocketWizard
, while giving a low voltage to the camera, can handle 200V from the flash port thus isolating the camera from the flash's high voltage trigger.
of the "Prontor/Compur
" shutters of the 1930s), or other accessories such as external light meter
s, special viewfinder
s, or rangefinder
s. These earlier accessory shoes were mostly the same U shape, and thus provided the template for the introduction of the hot shoe.
Canon, Nikon
, Olympus
, and Pentax
use the standard ISO hot shoe with various proprietary electronic connections. Since 1988, Minolta
has used a proprietary "iISO" connector
, and Konica Minolta
and Sony Alpha digital SLR cameras are based on Minolta designs and use the same connector.
, one can buy items such as a stereo microphone
or three different models of electronic viewfinder.
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
to attach a flash unit
Flash (photography)
A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light...
.
Design
The hot shoe is shaped somewhat like an inverted, squared-off "U" of metal. The matching adapter on the bottom of the flash unit slides in from the back of the camera and is sometimes secured by a clamping screw on the flash. In the center of the "U" is a metal contact point. This is used for standard, brand-independent flash synchronizationFlash synchronization
In a camera, flash synchronization is defined as the firing of a photographic flash coinciding with the shutter admitting light to photographic film or electronic image sensor. It is often shortened to flash sync or flash synch....
. Normally the metal of the shoe and the metal of the contact are electrically isolated from each other. To fire the flash, these two pieces are shorted together. The flash unit sets up a circuit between shoe and contact—when it is completed by the camera, the flash fires.
In addition to the central contact point, many cameras have additional metal contacts within the "U" of the hot shoe. These are proprietary connectors that allow for more communication between the camera and a "dedicated flash". A dedicated flash can communicate information about its power rating to the camera, set camera settings automatically, transmit color temperature data about the emitted light, and can be commanded to light a focus-assist light or fire a lower-powered pre-flash for focus-assist, metering assist or red-eye effect
Red-eye effect
The red-eye effect in photography is the common appearance of red pupils in color photographs of eyes. It occurs when using a photographic flash very close to the camera lens , in ambient low light. The effect appears in the eyes of humans and animals that have no tapetum lucidum, hence no...
reduction.
The physical dimensions of the "standard hot shoe" are defined by the International Organization for Standardization
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
ISO 518:2006.
Voltages
The trigger voltage (for a flash) between the center contact and the shoe have varied over the years, between manufacturers, and even in the same manufacturer. When the contacts with a shutter were mechanical contacts, the actual voltage did not matter too much as long as it did not cause arcing, but now with electronic triggering, it can cause problems.The ISO 10330 specification allows for a trigger voltage of 24 volts, some manufacturers, particularly Canon, ask for no more than 6 volts. Some older flashes may have a high voltage, sometimes in the hundreds of volts. .
It is possible to connect a high voltage triggering flash with a camera which can only tolerate 6 volts, through the use of an adaptor which isolates the two units. Also many radio triggers, e.g. PocketWizard
PocketWizard
The PocketWizard is a wireless radio triggering system for off-camera lighting developed in the late 1990s, by LPA Design. It requires a transmitter electrically connected to the camera, usually mounted on the camera's hot shoe to trigger a remote receiver connected to a remote flash unit via a PC...
, while giving a low voltage to the camera, can handle 200V from the flash port thus isolating the camera from the flash's high voltage trigger.
History and use
Before the 1970s, many cameras had an "accessory shoe" or "cold shoe", intended to hold flashes that connected electronically via an outboard "PC cable" (not meaning a computer: the term goes back to the synchronization methodFlash synchronization
In a camera, flash synchronization is defined as the firing of a photographic flash coinciding with the shutter admitting light to photographic film or electronic image sensor. It is often shortened to flash sync or flash synch....
of the "Prontor/Compur
Prontor-Compur
A Prontor-Compur connection is a standard 3.5 mm electrical connector used in photography to synchronize the shutter to the flash....
" shutters of the 1930s), or other accessories such as external light meter
Light meter
A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph...
s, special viewfinder
Viewfinder
In photography, a viewfinder is what the photographer looks through to compose, and in many cases to focus, the picture. Most viewfinders are separate, and suffer parallax, while the single-lens reflex camera lets the viewfinder use the main optical system. Viewfinders are used in many cameras of...
s, or rangefinder
Rangefinder
A rangefinder is a device that measures distance from the observer to a target, for the purposes of surveying, determining focus in photography, or accurately aiming a weapon. Some devices use active methods to measure ; others measure distance using trigonometry...
s. These earlier accessory shoes were mostly the same U shape, and thus provided the template for the introduction of the hot shoe.
Canon, Nikon
Nikon
, also known as just Nikon, is a multinational corporation headquartered in Tokyo, Japan, specializing in optics and imaging. Its products include cameras, binoculars, microscopes, measurement instruments, and the steppers used in the photolithography steps of semiconductor fabrication, of which...
, Olympus
Olympus Corporation
is a Japan-based manufacturer of optics and reprography products. Olympus was established on 12 October 1919, initially specializing in microscope and thermometer businesses. Its global headquarters are in Shinjuku, Tokyo, Japan, while its USA operations are based in Center Valley, Pennsylvania,...
, and Pentax
Pentax
Pentax is a brand name used by Hoya Corporation for its medical-related products & services and Pentax Ricoh Imaging Company for cameras, sport optics , etc. Hoya purchased and merged with the Japanese optics company on March 31, 2008. Hoya's Pentax imaging business was sold to Ricoh Company, Ltd...
use the standard ISO hot shoe with various proprietary electronic connections. Since 1988, Minolta
Minolta
Minolta Co., Ltd. was a Japanese worldwide manufacturer of cameras, camera accessories, photocopiers, fax machines, and laser printers. Minolta was founded in Osaka, Japan, in 1928 as . It is perhaps best known for making the first integrated autofocus 35mm SLR camera system...
has used a proprietary "iISO" connector
IISO flash shoe
iISO flash shoe is the inofficial name for the proprietary accessory flash attachment and control interface used on Minolta cameras since the i-series introduced in 1988, and subsequently Konica-Minolta and later Sony α DSLRs and NEX-7...
, and Konica Minolta
Konica Minolta
is a Japanese manufacturer of office equipment, medical imaging, graphic imaging, optical devices, and measuring instruments. It is headquartered in the Marunouchi Center Building in Marunouchi, Chiyoda, Tokyo, with a Kansai office in Nishi-ku, Osaka, Osaka Prefecture...
and Sony Alpha digital SLR cameras are based on Minolta designs and use the same connector.
Modern Cold Shoes
There is still a use for "Cold shoes" i.e., a shoe mount without the "hot" connection. These are often used with off-camera flash, with the flash mounted on a light stand, where the sync signal comes from either a photo slave or a radio trigger.Non flash items on the Hot Shoe
Manufacturers in the 21st century still make non-flash items which mount on the hot shoe of their cameras. For instance, for the Olympus XZ-1Olympus XZ-1
The Olympus XZ-1 is a high-end 10.0 megapixel compact digital camera announced and released in January 2011. Its key features are a fast f/1.8-2.5 i.Zuiko Digital lens, a built in imager shift image stabilizer and Olympus' 6 Art Filters that are also present in the E-PEN series.-Features:Key...
, one can buy items such as a stereo microphone
Microphone
A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...
or three different models of electronic viewfinder.