High-Speed Sync (HSS)

High-speed sync, or HSS, is a flash mode that allows flash at shutter speeds faster than the camera's sync speed. Instead of one burst, the flash fires a rapid series of pulses while the shutter slit moves across the sensor, so the whole frame receives even light. The mode appears on many speedlights and battery strobes and covers shutter speeds up to 1/8000 s on compatible cameras.

Focal-plane shutters use two curtains that travel across the sensor. At slower shutter speeds, the first curtain opens fully before the second starts moving, so one flash burst lights the entire frame. At faster speeds, the second curtain starts before the first finishes, and the sensor is exposed through a moving slit. A single burst then lights only the strip behind the slit, leaving dark bands. Most cameras set the limit near 1/200 s or 1/250 s.

HSS helps whenever flash and a fast shutter speed must work together. The most common case is an outdoor portrait at a wide aperture in bright sun, where a correct exposure needs 1/1000 s or faster. It also suits flash-lit action, such as sports or dancers outdoors, and any scene where the photographer wants a darker, more dramatic background in daylight.

Pulsing spreads the output over time, so HSS costs about two to three stops of power compared with a normal burst, and the loss grows as the shutter speed climbs. A flash that covers a subject at 3 meters in normal mode may need to sit within arm's reach in HSS. Larger battery strobes handle the loss better than small speedlights.

No. The flash, camera, and any radio trigger must all support the feature. Most current speedlights from major camera and lighting brands include it, as do many battery strobes made for location work. Basic manual flashes and older units often lack the mode. Spec sheets list it as HSS, FP sync, or focal plane sync depending on the brand.

Rear curtain sync changes when a single burst fires during a normal exposure: at the end instead of the start, which places motion trails behind the subject. It works at or below the sync speed. HSS changes how the flash fires, replacing the single burst with rapid pulses so flash works above the sync speed. The two modes solve different problems and generally cannot be combined.

Both let a wide aperture work with flash in bright light, by different routes. An ND filter cuts all incoming light so the shutter stays at the sync speed and the flash fires one full-power burst, which preserves power and battery life. HSS skips the extra glass and keeps the viewfinder bright, but costs two to three stops of flash output. Portrait shooters often carry both options.

Yes, but the shutter does the work rather than the flash. In normal mode, the short burst freezes motion even at slow shutter speeds. In HSS, the pulses behave like continuous light, so the shutter speed itself must stop the action. Speeds of 1/2000 s and faster freeze most sports and dance movement, as long as the flash sits close enough to light the subject.

Yes, when the radio trigger supports it. The trigger passes timing information from the camera to the remote flash so the pulses line up with the shutter slit. Mixed-brand setups need care, since a trigger, flash, and camera from three makers may not share the same HSS protocol. Dedicated trigger systems from the flash maker are the most reliable route.

A common starting point is the widest aperture the lens offers, ISO 100, and a shutter speed near 1/250 s. From there, the photographer raises the shutter speed until the sky or background reaches the wanted tone, then sets flash power to light the subject. Because HSS cuts output, the light often sits 1 to 2 meters from the subject, frequently in a small softbox.