photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...

, flash synchronization or flash sync is the synchronizing the firing of a

photographic flash A flash is a device used in photography that produces a brief burst of light (lasting around of a second) at a color temperature of about 5500 K to help illuminate a scene. The main purpose of a flash is to illuminate a dark scene. Other use ...

with the opening of the shutter admitting light to

photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...

or electronic

image sensor An image sensor or imager is a sensor that detects and conveys information used to form an image. It does so by converting the variable attenuation of light waves (as they refraction, pass through or reflection (physics), reflect off objects) into s ...

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

s with mechanical (

clockwork Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement (clockwork), movement) or other mechanisms that work similarly, using a series of gears driven by a spring or wei ...

) shutters synchronization is supported by an

electrical contact An electrical contact is an Electronic component, electrical circuit component found in electrical switches, relays, Electrical connector, connectors and circuit breakers. Each contact is a piece of electrically conductive material, typically meta ...

within the shutter mechanism, which closes the circuit at the appropriate moment in the shutter opening process. In electronic

digital camera A digital camera, also called a digicam, is a camera that captures photographs in Digital data storage, digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film or film stock. Dig ...

s, the mechanism is usually a programmable electronic timing circuit, which may, in some cameras, take input from a mechanical shutter contact. The flash is connected electrically to the camera either by a cable with a standardized coaxial PC (for Prontor/Compur) connector (as defined in ISO 519), or via contacts in an ''accessory mount'' (

hot shoe Canon EOS 350D Hot shoe Proprietary hot shoe used by Minolta and older Sony cameras (Konica Minolta Maxxum 7D)">Sony">Minolta and older Sony cameras (Konica Minolta Maxxum 7D">Sony.html" ;"title="Minolta and older Sony">Minolta and older Sony ...

) bracket. Faster shutter speeds are often better when there is significant ambient illumination, and flash is used to flash fill subjects that are backlit without

motion blur Motion blur is the apparent streaking of moving objects in a photograph or a sequence of frames, such as a film or animation. It results when the image being recorded changes during the recording of a single exposure, due to rapid movement or l ...

, or to increase

depth of field The depth of field (DOF) is the distance between the nearest and the farthest objects that are in acceptably sharp focus (optics), focus in an image captured with a camera. See also the closely related depth of focus. Factors affecting depth ...

by using a small

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

. In another creative use, the photographer of a moving subject may deliberately combine a slow shutter speed with flash exposure in order to record motion blur of the ambient-lit regions of the image superimposed on the flash-lit regions.

X sync

X-sync (for ''xenon sync'') is the simplest mode; the

xenon Xenon is a chemical element; it has symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

flash is fired at the instant the shutter is fully open.

Electronic flash A flash is a device used in photography that produces a brief burst of light (lasting around of a second) at a color temperature of about 5500 K to help illuminate a scene. The main purpose of a flash is to illuminate a dark scene. Other use ...

equipment produces a very short flash. X sync is a mode designed for use with electronic flash. In this mode, the timing of the contacts coincides exactly with the full opening of the shutter, since xenon flashes respond almost instantly. Due to their construction, focal plane shutters, as used on most

single-lens reflex camera In photography, a single-lens reflex camera (SLR) is a type of camera that uses a mirror and prism system to allow photographers to view through the lens and see exactly what will be captured. SLRs became the dominant design for professional a ...

s (SLRs), only allow normal xenon flash units to be used at shutter speeds slow enough that the entire shutter is open at once, typically at

shutter speed In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light (that is, when the camera's shutter (photography), shutter is open) when taking a photograph. The am ...

s of 1/60 or slower, although some modern cameras may have an X-sync speed as high as 1/500 (e.g. Nikon's D40

DSLR A digital single-lens reflex camera (digital SLR or DSLR) is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor. The reflex des ...

s). Special electronic flash units for focal-plane shutters fire several times as the slit moves across the film. Electronic shutters used in some digital cameras do not have this limitation and may allow a very high X-sync speed.

S, M, ME, F, FP, and V sync

Cameras designed for use with

flash bulb A flash is a device used in photography that produces a brief burst of light (lasting around of a second) at a color temperature of about 5500 K to help illuminate a scene. The main purpose of a flash is to illuminate a dark scene. Other use ...

s generally had one or more of S (slow) sync, M (medium) sync, F (fast) sync, or FP/FPX (flat peak) sync, designed for use with corresponding bulb types. These sync modes close the contacts a few milliseconds before the shutter is open, to give the flashbulb time to reach peak brightness before exposing the film. Class M bulbs reach their peak illumination 20 milliseconds after ignition, and class F lamps reach their peak at approximately 5 milliseconds. FP sync was used with FP (flat-peak) flash bulbs designed specifically for use with

focal-plane shutter In camera design, a focal-plane shutter (FPS) is a type of photographic shutter that is positioned immediately in front of the focal plane of the camera, that is, right in front of the photographic film or image sensor. Two-curtain shutters ...

s. In these shutters, although each part of the film is exposed for the rated exposure time, the film is exposed by a slit which moves across the film in a time (the "X-sync speed") of the order of 1/100"; although the exposure of each part of the film may be 1/2000", the last part of the film is exposed later by the X-sync time than the first part, and a brief flash will illuminate only a strip of film. FP bulbs burned close to full brightness for the full X-sync time, giving time for the moving slit to expose the whole frame with the light of the flash. The

Nikon F The Nikon F camera, introduced in April 1959, was Nikon Corporation, Nikon's first Single-lens reflex camera, SLR camera. It was one of the most advanced cameras of its day. Although many of the concepts had already been introduced elsewhere, it ...

offered FP, M, and ME bulb synchronizations, in addition to the X sync. The

Friedrich Deckel Friedrich Deckel GmbH, also known as F.Deckel, was a German company founded by Friedrich Deckel and Christian Bruns in Munich as Bruns & Deckel in 1903. Its most famous product is the ''Compur'' line of leaf shutters used on many photographic lense ...

Synchro-Compur Friedrich Deckel GmbH, also known as F.Deckel, was a German company founded by Friedrich Deckel and Christian Bruns in Munich as Bruns & Deckel in 1903. Its most famous product is the ''Compur'' line of leaf shutters used on many photographic lense ...

leaf shutter In photography, a shutter is a device that allows light to pass for a determined period, exposing photographic film or a photosensitive digital sensor to light in order to capture a permanent image of a scene. A shutter can also be used to allow ...

of the

Braun Paxette Reflex Carl Braun Camera-Werk of Nuremberg, Germany, or Braun, as it was more commonly called, was founded as an optical production house. It is best known for its 35mm film cameras named Paxette, and for slide projectors named Paximat. History The c ...

offered V, X, and M flash synchronization, whereby V (German: "Vorlauf") was used in conjunction with self-timer.

High-speed sync (HSS)

Some modern xenon flash units have the ability to produce a longer-duration flash to permit flash synchronization at shorter shutter speeds, therefore called high-speed sync (HSS). Instead of delivering one burst of light, the units deliver several smaller bursts over a time interval as short as 1/125 of a second. This allows light to be delivered to the entire area of the film or image sensor even though the shutter is never fully open at any moment, similar to FP sync.

Rear-curtain sync

Many digital SLRs include an option to fire the flash just before the closing of the shutter, so that moving objects will show a streak where they came from and a sharp image where they were at the end of the exposure—useful for moving objects to convey a sense of speed. This mode is called ''rear-curtain sync'' or ''2nd-curtain sync''.

References

{{Photography Flash photography Photographic lighting