High-speed sync (HSS) is a technique that allows you to synchronize your flashlight output with your shutter to expose an image.
There is a limit to the shutter speed and the camera’s native sync. So what can we do?
Read on for all the information on how high-speed sync works you will ever need to know.
4. What Is High-Speed Sync?
As we mentioned, a flash syncs with the shutter speed of a camera. Most DSLRs have a native sync of 1/250th of a second. Anything faster than this (i.e. 1/500th) is beyond the camera’s ability to sync.
When the shutter and flash don’t sync correctly, you get a bad image. The flash will partly cover your scene, as seen in your images.
If you happen to encounter a scene that requires a faster shutter speed, you’re in trouble. You will over-expose your image and will start to create black bars over your image.
These black bars are areas where the flash is stopped by the shutter curtains.
By using higher shutter speeds, your focal plane is small. Your entire sensor is only capturing part of the image. To compensate, your strobes will pulse after 1/200th of a second.
This means the only time the light from the strobe is available is in-between your shots.
3. When to Use High-Speed Sync?
You’ll want to use high-speed sync when you’re using a high shutter speed that is faster than your camera’s flash sync speed.
An HSS is also very beneficial for scenes with a very bright background, where your subject is in the shade. Think of outdoor portraits, for example, when you’ll want to use a wider aperture.
A wide aperture to keep a shallow depth of field will force your shutter speed to around 1/800th of a second.
At this fast speed, you will not be able to sync your strobes or flash units, unless you use the high-speed sync technique.
The only way to capture the subject in the shade with a correct exposure is to use high-speed sync. You’ll have more control over the light.
You wouldn’t be able to do this without high-speed sync as the background is brighter than 1/200th of a second.
A curtain shutter falls much faster at 1/100oth of a second compared to 1/200th of a second. The flash needs to start and end while the shutter curtain is open. Only HSS can do this.
2. How to Use High-Speed Sync
A flash in high-speed sync acts similar to a constant light. The faster your shutter speed is, the darker the ambient light will get. This is where you see flash power reduce over higher shutter speeds.
First, you need a light source other than the natural light hitting your background. There are many mono-light manufacturers you can use, such as Baja, Profoto or Flashpoint.
Second, place your model in the shade while you photograph a well-lit background.
Aim for getting the depth of field you want first. You don’t want to change the aperture and shutter speeds at the same time while working with the mono-light.
Set the exposure value to the background. This is because we can’t add or take away light from the background. We can strengthen the light falling on the subject.
Third, set up your light. Attach the receiver to your camera and turn everything on. Hold down the high-speed sync button on the receiver to turn it on.
Next, press the HSS button on the back of the light. Start with H5 or anywhere in the mid-level power output. From there you can increase or decrease the power for the correct exposure on your subject.
1. How Does High-Speed Sync Work
As we pointed out before, with shutter speeds, anything above 1/200th of a second is unmanageable with a normal flash feature. At 1/1000th of a second, the curtain falls too fast for the flash to light up the entire image.
When you set your flash unit to working with high-speed shutters, something magical happens. The flash or strobe will pulse bursts of light, faster than normal.
This action ensures the entire image is lit correctly. The only difference is the rate at which the flash can fire, activated by the HSS feature on the flash unit.
Set your shutter speed, then dial it into your strobes. That’s the secret! When you change your shutter speed faster or slower, make sure you change the settings on the strobe.
This works wonders when your aperture isn’t changing. Start off by getting the depth of field you want. This way, you won’t be confused by changing many variables at the same time.
There are only two downsides that I can see with this technique. One is that you get this high-speed sync advantage is having to use your mono-light on full power for a lot longer. Goodbye battery.
The second is you may find limitations set by the time of day you want to use this technique.
Here’s to your perfectly exposed image.
If you want to read more on flash photography, check out this guide on flash modes TTL vs Manual Flash.
A note from Josh, ExpertPhotography's Photographer-In-Chief:
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