Flash synchronization
Encyclopedia
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...
, flash synchronization is defined as the firing of a photographic flash coinciding with the shutter
Shutter (photography)
In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene...
admitting light to photographic film
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
or electronic image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
. It is often shortened to flash sync or flash synch.
In mechanical cameras, the synchronization mechanism usually consists of an electrical contact within the shutter
Shutter (photography)
In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene...
mechanism. In electronic digital camera
Digital camera
A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...
s, the mechanism is usually a programmable electronic timing circuit, which may take input from a mechanical shutter contact in some cameras. The electrical connection will be either by means of a cable with a standardised coaxial PC
Prontor-Compur
A Prontor-Compur connection is a standard 3.5 mm electrical connector used in photography to synchronize the shutter to the flash....
(for Prontor/Compur) 3.5 mm (1/8") connector (as defined in ISO 519), or via contacts in an accessory mount (hot shoe
Hot shoe
A hot shoe is a mounting point on the top of a camera to attach a flash unit.- 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...
) bracket.
In general, faster flash sync speeds, usually rated in fractions of a second, are better if the photographer needs to flash-fill subjects that are backlit and wants to avoid motion blur
Motion blur
Motion blur is the apparent streaking of rapidly moving objects in a still image or a sequence of images such as a movie or animation. It results when the image being recorded changes during the recording of a single frame, either due to rapid movement or long exposure.- Photography :When a camera...
, or wants to increase depth of field
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...
by using a high aperture
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are,...
.
M, F, FP, X and HSS sync
Cameras designed for use with flash bulbs generally had one or more of M (medium) sync, F (fast) sync, or FP (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 put the main pulse of light at the best time relative to the shutter opening. Class M bulbs reach their peak of illumination at around 20-25 milliseconds, and class F lamps reach their peak at approximately 5 milliseconds. X sync closes the flash contact just as the shutter blades are almost completely open, and M sync closes the flash contact 20 milliseconds before the blades are completely open. FP sync was designed for use with FP (flat-peak) flash bulbs which were designed for use with focal-plane shutterFocal-plane shutter
In camera design, a focal-plane shutter 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. Most standard flash bulbs used M sync.
The Nikon F
Nikon F
The Nikon F camera, introduced in 1959, was Nikon's first SLR camera. It was one of the most advanced cameras of its day. Although most of its concepts had already been introduced elsewhere, it was the first camera to combine them all in one camera. It was produced until October 1973 and was...
offered FP, M, and ME bulb synchronizations, in addition to the X sync.
X (xenon) 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
Xenon
Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced or . A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
flashes respond almost instantly.
Due to their construction, focal plane shutters, as used on most SLRs
Single-lens reflex camera
A single-lens reflex camera is a camera that typically uses a semi-automatic moving mirror system that permits the photographer to see exactly what will be captured by the film or digital imaging system, as opposed to pre-SLR cameras where the view through the viewfinder could be significantly...
, will only allow xenon flash units to be used at shutter speeds slow enough that the entire shutter is open at once, typically at shutter speed
Shutter speed
In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open....
s of 1/60 or slower, but some modern cameras may have an X-sync speed as high as 1/500 (e.g. Nikon's D40
Nikon D40
The D40 is a now-discontinued Nikon F-mount entry-level digital SLR, announced November 16, 2006. Compared to its predecessor, the D50, the D40 had several features removed, a few added, and a lower price: US$499.95 ESP as of November 2009 with the 18–55 mm G-II kit lens, positioning it as an...
DSLRs). Electronic shutters used in some digital cameras do not have this limitation and may allow a very high X-sync speed.
Leaf shutters, which are generally situated within the lens housing, open to expose the entire image at once, and therefore allow flash sync across all shutter speeds (up to 1/1000 with a Rollei PQS lens).
Higher sync speeds are useful as they enable the brightness of the background to be controlled while maintaining normal flash exposure in the foreground, for example with a back-lit subject.
Today, certain 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 a time interval as short at 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. The downside is that the flash is of less effective intensity since the individual bursts are lower powered than the normal capability of the flash unit. Only certain camera and flash combinations support this feature, and the camera-flash pairings are almost exclusively from the same manufacturer, the first being the Olympus OM-4
Olympus OM-4
The Olympus OM-4 is an interchangeable lens, 35 mm film, single lens reflex camera; manufactured by Olympus Optical Co., Ltd. in Japan and sold as OM-4 from 1983 to 1987 and as OM-4Ti from 1986 to 2002....
with the F280 flashgun. Wireless flash units with this feature are currently very rare.
Rear-curtain sync
Some modern electronic cameras include the ability 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 either rear-curtain sync or 2nd-curtain sync.Wireless sync
Some synchronization methods employ optical or radio triggering that require no electrical connection to the camera or main flash unit. This allows the camera to move without the restriction of cables. Optical triggering requires at least one flash electrically connected to the camera. A sensor either built-in or external to a remote slave flash unit will sense the light from the master flash and tell a remote flash to fire. RadioRadio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
triggering requires a transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
electrically connected to the camera
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 trigger a remote
Remote control
A remote control is a component of an electronics device, most commonly a television set, used for operating the television device wirelessly from a short line-of-sight distance.The remote control is usually contracted to remote...
receiver
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
connected to a remote flash
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...
unit.
One of the problems with optical triggering is that in modern digital camera's the in-built flash releases one or more 'pre-flashes'. Many optical slave units will respond to the pre-flash thus firing the slave flash too early. Sometimes this can be prevented by setting the camera to manual ('M'). However, a good number of camera's will still fire pre-flashes even on a manual setting. This is equally true for the compact camera's as well as the more professional digital SLR camera's. Still, a flash connected to the PC jack on a camera or in the hotshoe, will usually not fire pre-flashes in the 'M' setting and therefore can be used to optically trigger a number of slave flashes.
Many compact camera's however, only have a built in flash and no hotshoe and no connector for an external flash and there is no way to avoid the suppress the pre-flash. In those instances, slave units are used that are able to skip a number of flashes, thus skipping one or more pre-flashes and only firing simultaneously with the main flash firing.
Modern flash units have this capacity built in. At the low end e.g. is the Godox 18, a simple flash unit that can be set to skip a max of 3 flashes. A more advanced flash that can set to skip one preflash is the popular 'strobist' flash the Lumopro160. Also some studio flashes can be set to ignore pre-flash.
Rather than selecting a special amount of preflashes to ignore, Some slave units have a learning mode in which firing one flash teaches them on which flash to synchronise.
See also
- Flash (photography)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...
- Focal-plane shutterFocal-plane shutterIn camera design, a focal-plane shutter 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:...
- Through-the-lens meteringThrough-the-lens meteringThrough-the-lens metering is a photographic term describing a feature of cameras capable of measuring light levels in a scene through their taking lenses, as opposed to a separate metering window...
(TTL) - PocketWizardPocketWizardThe 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...