High-Speed Sync – When the flash is faster than the shutter – Or: How to shoot with flash and open aperture in sunny conditions
There are moments in photography when you want everything at once: open aperture for beautiful bokeh, great lighting mood in the midday sun and a clean flash effect on top.
The only problem is that your camera suddenly says “Nope, flash doesn’t work” at 1/1000 s.
And this is exactly where High-Speed Sync, or HSS for short, comes into play – the superhero among the flash functions.
What is High-Speed Sync anyway?
Normally, a flash can only be used with relatively slow shutter speeds – with most cameras, this so-called sync speed is 1/200 s or 1/250 s.
Why? Because the shutter consists of two blades that move across the sensor like a slit at short speeds. When the flash fires, only part of the sensor is open – the image becomes partially dark.
High-Speed Sync does things differently:
The flash fires not just once, but several times in succession in ultra-fast pulses as the slit moves across the sensor. This ensures that every part of the sensor is evenly exposed – even at 1/4000 s or 1/8000 s.
Think of it as a mini strobe flash that “flickers” along with the shutter.
When is HSS used?
HSS is always exciting when you need very fast shutter speeds and want to flash at the same time. Typical situations:
1st portrait in daylight with open aperture
You want f/1.8 – but the sun is glaring. To expose correctly, you would have to go to 1/2000 s or faster.
→ You can’t do it without HSS. With HSS: Sharp portrait, soft background, controlled light.
2. freeze movement
A skater jumps through the air, you want to “freeze” him – and still put some light on his face.
→ With HSS you can capture the moment and set targeted light.
3. creative lighting design with backlighting
The sun is shining into your picture, but you still want to expose your subject perfectly without everything “burning out”.
→ HSS gives you full control – over the subject and background at the same time.
How does HSS work technically? (Don’t worry, clearly explained)
Normal flashes fire a short pulse of light – perfect at shutter speeds up to approx. 1/200 s.
From approx. 1/250 s, however, the entire sensor is never open – only a wandering slit.
HSS flashes pulse synchronized over the entire exposure time – so every part of the sensor is exposed without streaks or dropouts.
Important: Your flash AND your radio transmitter must support HSS. Otherwise it won’t work.
Advantages of High-Speed Sync
✔️ You can take photos in daylight with an open aperture
✔️ You can darken the background, make the subject bright
✔️ You don’t need an ND filter if you have HSS
✔️ You have full creative freedom – in sun AND flash
Disadvantages – where HSS reaches its limits
❌ Less power – As the flash pulses several times, the energy is distributed – the brightness decreases significantly.
❌ Battery guzzler – HSS is exhausting for the flash. Batteries are drained more quickly, charging times are longer.
❌ Not every flash can do HSS
You need HSS-capable devices – often more expensive, not always compatible with older cameras.
❌ It gets difficult over long distances
If you want to illuminate a large area outdoors, you will quickly reach the power limit.
Conclusion: When is HSS worthwhile – and when is it not?
HSS is perfect for:
- Portraits with bokeh in daylight
- Backlit situations with targeted brightening
- Reportage with fast light changes
- Creative flash looks “on location”
HSS is less useful if:
- You want to illuminate large rooms or backgrounds evenly
- You are working with a closed aperture and slow time anyway
- Battery life or maximum performance are more important to you than flexibility
Tip from the field
If you are shooting outside with flash and want to use HSS, start with the following values:
- Camera: 1/2000 s, f/2.8, ISO 100
- Flash: HSS activated, high power (e.g. 1/1 to 1/2)
- Take a test picture, if necessary use a flash closer to the subject or a reflector
Alternatively: Use an ND filter if you prefer to stay in normal flash mode and do not have an HSS function.
