Flash synchronization
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In photography, flash synchronization or flash sync is the synchronizing the firing of a photographic flash with the opening of the shutter admitting light to photographic film or electronic image sensor.
In cameras with mechanical (clockwork) shutters synchronization is supported by an electrical contact within the shutter mechanism, which closes the circuit at the appropriate moment in the shutter opening process. In electronic digital cameras, 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) 3.5 mm (1/8") connector[1] (as defined in ISO 519[2]), or via contacts in an accessory mount (hot shoe) bracket.
Faster shutter speeds are often better when there is significant ambient illumination, and flash is used to
X sync
X-sync (for xenon sync) is the simplest mode; the
Due to their construction, focal plane shutters, as used on most
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
FP sync was used with FP (flat-peak) flash bulbs designed specifically for use with focal-plane shutters. 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 offered FP, M, and ME bulb synchronizations, in addition to the X sync.[5]
The
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.[6][7] This mode is called rear-curtain sync or 2nd-curtain sync.[6][7]
See also
References
- ISBN 0-240-51574-9.
- ^ ISO 519:1974, ISO 519:1992 (November 25, 1992). Photography -- Hand-held cameras -- Flash-connector dimensions. Geneva: International Organization for Standardization.
- ISBN 0-02-864387-9.
- ^ Confused about flash bulbs Graflex.org
- ISBN 1-57990-592-7.
- ^ a b Sahlin, Doug. "How to Use Second Curtain Sync on Your Canon EOS 6D". Dummies.com. John Wiley & Sons. Retrieved June 28, 2021.
- ^ a b Farren, Peggy (2019). "Front and Rear Curtain Sync on your Flash". UnderstandPhotography.com. Retrieved June 28, 2021.