High speed sync is a flash mode that lets you use shutter speeds faster than the camera normal flash sync speed. Instead of one short burst, the flash fires a rapid series of pulses while the shutter slit travels across the sensor. This allows wide apertures in bright light, at the cost of much lower flash power.
Why It Matters
Outdoors in sunshine you often want a wide aperture for a blurred background. That needs a fast shutter speed, but ordinary flash sync stops at about 1/200 or 1/250 second, so the picture is overexposed.
High speed sync solves this and lets you fill shadows with flash while keeping background blur. Knowing its limits helps you decide when to use it and when a neutral density filter or a stronger flash is better.
Beginner High Speed Sync Flash For Beginners
With a focal plane shutter, two curtains move across the sensor. At slow speeds the first curtain opens fully before the second one starts to close, so a single flash lights the entire frame. At fast speeds the second curtain starts before the first has finished, so only a moving slit is open at any moment. A single flash would light only a band of the picture.
What High Speed Sync Does
In this mode the flash fires a long train of very fast pulses that behaves almost like continuous light for the time the slit travels. Every part of the sensor gets light. The picture is evenly lit at speeds like 1/1000 or 1/8000 second.
When To Use It
| Situation | Why High Speed Sync Helps |
|---|---|
| Portraits in bright sun at f/1.8 | Fast shutter keeps exposure correct while flash fills the face |
| Freezing action outdoors | Allows short shutter times without losing the flash |
| Overpowering the sun for a dramatic sky | Lets you underexpose the background and add light to the subject |
| Outdoor fashion or sport portraits | Combines shallow depth of field with controlled light |
How To Turn It On
- Use a flash and camera that support it. Look for an HSS or FP setting on the flash, or high speed in the camera flash menu.
- Set the camera to Aperture Priority or Manual and pick your aperture.
- Choose a shutter speed above the normal sync speed, such as 1/1000 second.
- Take a test shot and adjust flash power or aperture until the face looks natural.
Common Mistakes
- Using it when you do not need it. Below the sync speed, normal flash is more powerful and uses less battery.
- Standing too far away. The pulses are weak, so the subject must be close, often within 6 to 10 feet.
- Forgetting to enable it, which gives a black band across the image at fast speeds.
- Expecting the same reach as normal flash, then wondering why the light looks weak.
A Starting Recipe For Sunny Portraits
Put the subject with the sun at their side or back and the flash on a stand about 4 feet away. Set Manual, ISO 100, f/2.8 and 1/1000 second, then adjust the flash power until the face is bright without looking lit. If shadows are too dark, move the flash closer or open the aperture. Take a few frames and check the histogram so the sky is not blown out.
Handy for this: Speedlight Flash — add light anywhere. (affiliate link)
Advanced Power Loss, Duration And Alternatives
Why Power Drops
The flash must spread its energy across a long series of pulses, and each pulse is only a small fraction of full power. A flash that delivers a guide number of 60 meters at normal sync might deliver the equivalent of about 30 or less at 1/4000 second. See flash guide number for the math behind these figures. Each doubling of shutter speed beyond sync costs roughly a stop of effective flash power, though the exact amount depends on the model.
Flash Duration And Motion Freezing
HSS does not freeze action as well as a single short burst. A regular flash at low power can last 1/20,000 second or shorter, but pulsed light behaves like long duration light, so freezing depends on the shutter speed instead. For true motion freezing in dim conditions, use a short flash at normal sync speed, as described in flash duration.
Flash Types And Compatibility
- Speedlights from major brands support HSS with matching cameras, often through TTL communication.
- Many studio strobes cannot do HSS, because their flash tubes are built for single bursts and long recycle times.
- Some strobes have a pulse or hypersync feature, or use IGBT circuits to produce a long flat flash.
- Radio triggers must pass HSS information, so check that your trigger and receiver support it. See flash triggers.
Alternatives To HSS
A neutral density filter lowers the ambient light and lets you stay below sync speed while keeping a wide aperture. A 3-stop ND turns a 1/2000 setting into 1/250. This keeps full flash power, shorter flash duration and less battery use, but it dims the viewfinder and adds a filter to carry. A leaf shutter lens syncs with flash at any speed, and some mirrorless cameras offer electronic shutter flash modes, though they come with their own limits. Read about ND filters as a tool for bright light.
Balancing Flash And Ambient
Shutter speed controls the ambient exposure and aperture controls both flash and ambient. In HSS, a faster shutter darkens the background without changing the flash power much, until the pulses become weak. Set ambient first, then adjust flash power to the amount of fill you want. For natural results, keep the flash about one to two stops under ambient for fill, or use it as the main light for dramatic portraits. The lesson on ambient and flash explains the balance in detail.
Battery And Heat
HSS drains batteries quickly and heats the flash head, so use fresh batteries, an external pack or lithium cells for long sessions. Many speedlights reduce output or stop firing to protect themselves when overheated.
Try It
- On a sunny day, place a friend in open shade or sun with the camera in Manual mode.
- Set f/2 and 1/200 second without flash. Note how overexposed the background is.
- Turn on HSS, raise shutter speed to 1/2000 second, and add flash at about half power.
- Compare the background blur and sky color with the first test.
Common Questions
What is the normal flash sync speed?
Most focal plane shutters sync at 1/160 to 1/250 second. The exact value is listed in your camera manual, and many mirrorless cameras with mechanical shutters sit around 1/200 or 1/250.
Does high speed sync reduce flash range?
Yes. The flash output is divided among many pulses, so the effective power at 1/4000 second may be a quarter of its normal full-power output. Move the flash closer or open the aperture.
Can I use HSS with off-camera flash?
Yes, if your triggers and flashes support it. Radio systems from camera makers and several third-party brands pass HSS commands to compatible flashes.
Is HSS better than an ND filter?
Neither is always better. HSS is convenient and needs no filter, while an ND filter keeps full flash power. Use HSS for quick work and ND for stronger light.
Related Lessons
- Off-Camera Flash to place the light for better portraits.
- Flash Guide Number for how flash power and range are measured.
- Ambient And Flash to balance flash with existing light.
- Flash Triggers for radio systems that pass HSS signals.
- Rear-Curtain Sync for another way to control timing with flash.
Gear That Helps With This
Hand-picked kit that makes this lesson easier to put into practice.
Some links are affiliate links: if you buy through them we may earn a small commission at no extra cost to you. How this works.