Flash photography can be transformative — but knowing which sync mode to use and when is what separates good shots from great ones. Whether you're shooting outdoor portraits in harsh sunlight or capturing atmosphere at a nighttime event, understanding high speed sync (HSS) and low speed sync flash will give you far greater creative control. Browse our range of flash guns & camera lighting to find the right gear for your setup.
What is High Speed Sync (HSS) Flash Photography?
High speed sync flash photography is a technique that allows photographers to use flash at shutter speeds faster than their camera's native sync speed (typically 1/200s–1/250s). This is crucial for overcoming limitations when using flash in bright ambient light — it enables the use of wider apertures for shallow depth of field and eliminates motion blur caused by fast-moving subjects.
By synchronising the flash pulse with the camera's shutter curtain movement across the entire sensor, HSS ensures proper exposure across the whole image — resulting in well-lit, sharp photographs even in the most challenging lighting conditions.
Putting High Speed Sync Techniques to Use
Photographers commonly reach for HSS flash in these scenarios:
- Outdoor Portraits: Overpower harsh sunlight and shoot at wider apertures (f/1.4–f/2.8) for beautiful background blur and flattering subject separation.
- Action Photography: Freeze fast motion in brightly lit environments where a fast shutter speed is essential.
- Fill Flash in Sunlight: Eliminate harsh shadows on subjects shooting in direct sunlight, while maintaining a fast shutter speed.
- Wedding Photography: Control ambient light during outdoor ceremonies and receptions for consistently flattering portraits.
- Sports Photography: Capture crisp, well-lit images of athletes in action, even in bright daylight.
- Wildlife Photography: Freeze fast-moving animals while using a wide aperture to blur distracting backgrounds.
What is Low Speed Sync Flash Photography?
Low speed sync (also called slow sync) flash photography combines a slow shutter speed with a flash burst to create a balanced exposure between the subject and the ambient background. Unlike HSS — which prioritises freezing motion — slow sync aims to capture both the flash-lit subject and the surrounding environment illuminated by ambient light.
This technique is particularly powerful in low-light situations, where it allows for brighter backgrounds and creative motion blur effects, resulting in images that feel more natural, atmospheric, and cinematic.
Putting Low Speed Sync Techniques to Use
Photographers commonly use slow sync flash in these situations:
- Nighttime Portraits: Illuminate the subject with flash while capturing the ambient glow of the background for a balanced, natural-looking exposure.
- Event Photography (Parties & Receptions): Capture both the subject and the atmosphere of the event — including background lighting and movement.
- Creative Motion Blur: Combine a sharp flash-lit subject with intentional blur of the background or subject for striking artistic effects.
- Indoor Architecture & Interiors: Light a subject with flash while retaining the ambient warmth of the room, avoiding a stark or artificial look.
- Light Painting: Combine long exposures with flash bursts to create light trails and selectively illuminate areas of a scene.
- Cityscapes at Night: Illuminate a foreground subject with flash while capturing the city lights and atmosphere in the background.
Frequently Asked Questions: HSS & Slow Sync Flash
What is high speed sync flash?
High speed sync (HSS) is a flash mode that allows you to shoot at shutter speeds faster than your camera's maximum sync speed (typically 1/200s–1/250s). It works by pulsing the flash rapidly as the shutter curtain travels across the sensor, ensuring even exposure at any shutter speed. It's essential for shooting with flash in bright conditions or when using wide apertures outdoors.
What is a camera's native sync speed?
A camera's native sync speed (also called the X-sync speed) is the fastest shutter speed at which the entire sensor is exposed at once — typically between 1/160s and 1/250s depending on the camera model. At speeds faster than this, the shutter curtain begins to cover part of the sensor before the other curtain opens, causing a dark band across the image if a standard flash is used. HSS overcomes this limitation.
When should I use HSS vs slow sync flash?
Use HSS when shooting in bright conditions and you need a fast shutter speed — for example, outdoor portraits in sunlight, action shots, or any situation where you want a wide aperture with flash. Use slow sync when shooting in low light and you want to retain background detail and atmosphere — such as nighttime portraits, events, or creative long-exposure work.
Does HSS reduce flash power?
Yes — HSS is less power-efficient than standard sync because the flash pulses continuously rather than firing a single burst. This means effective flash range is reduced, and batteries drain faster. For this reason, HSS works best at closer distances or with more powerful flash units. It's a trade-off worth making when the creative result demands it.
What is rear curtain sync and how does it differ?
Rear curtain sync (also called second curtain sync) fires the flash at the end of the exposure rather than the beginning. This means any motion blur trails appear behind the subject rather than in front, creating a more natural sense of movement. It's commonly used in combination with slow sync for creative motion blur effects at events or with moving subjects.
Do I need a special flash for HSS?
Yes — not all flash units support HSS. You'll need a compatible speedlight or strobe that supports HSS for your specific camera brand. Check our range of flash guns & camera lighting to find HSS-compatible options, and always verify compatibility with your camera body before purchasing.
Ready to Take Your Flash Photography Further?
Now that you understand sync speeds, dive deeper into the world of flash with these related guides:
- Everything You Need To Know About Flash Photography — the complete beginner-to-advanced overview
- Flash vs. Constant Light: What's the Best Lighting for Photography? — help choosing the right light source
- Using Flash for Better Macro Photography — specialist flash techniques for close-up work
Explore our full range of flash guns & camera lighting at Ted's Cameras, and check out our studio lights & photography lighting range for more advanced setups.