The Usefulness of High-Speed Sync
High-speed sync (HSS) is easily one of the most useful features in lighting. Not only does it let you overpower the sun for more flattering light in the middle of the day, it also lets you use your largest apertures in broad daylight.
It also lets you use another useful technique – underexposing your backgrounds by several stops. With a powerful enough light you can even underexpose the sun by three or four stops, thus making it a compositional element in your frame. This lets you create dark, dramatic backgrounds for visual impact. It also brings your subject forward in the frame, ensuring they’re the dominant aspect of your image.
Fortunately, using HSS to create dark backgrounds like this is easy. And in this short tutorial, I’ll show you how to do it using both E-TTL and manual exposure modes.
Why Darken Your Backgrounds?
While you won’t want to darken the background in every situation, dark backgrounds in scenes that would normally be very bright look great. It may be a stylised affair, but it’s a cool style.
Darkening the background brings your subject forward in the frame(providing they’re well lit), and emphasizes them as the focal point of the background. And the inherent contrast added by putting extremely dark tones in the frame helps to make things pop.
What Do You Need?
To get started with this technique you’ll need:
- A flash with HSS capability (and TTL capability if you don’t want to use manual).
- A trigger or some other means to fire your flash. (You’ll need a TTL-compatible trigger if you want to use TTL.)
To use this technique with TTL metering, turn on the flash, trigger, and camera of whatever system you’re using. Set your flash mode to HSS and E-TTL. (If you don’t know how to do this, refer to your manual.) You should also zero out the flash exposure compensation settings on your flash.
Now dial between -1 and -3 stops of exposure compensation into your camera. What this does is underexpose all the ambient light in your scene. It’s how you achieve the dark backgrounds – everything that isn’t properly exposed by your flash will be darkened.
For dark backgrounds already in shadow, -1 stop of exposure compensation will be enough. For bright backgrounds or backgrounds in direct sunlight, you’ll need to underexpose more. To overpower the sun, you’ll need to underexpose by at least three stops.
Take a test shot, evaluate the image and the histogram on your camera, and adjust the flash exposure compensation as needed.
That’s all there is to it.
The steps for manual mode are almost identical to using E-TTL mode.
- Set up the flash, trigger, and camera of your system.
- Set the camera to aperture priority mode.
- Set the camera to your desired aperture.
- Dial in -1 to -3 stops of exposure compensation.
- Take a test shot.
- Adjust your flash power as needed.
However, in manual mode, the meter in your camera doesn’t relay any exposure information to your flash as it does in E-TTL mode. That means you’ll need to set your flash power yourself by evaluating your test shot and turning the flash power up or down as needed. You may need to alter the flash power a lot more than you would with E-TTL. Just keep taking tests shots and evaluating the exposure until it’s where you want it.
As an aside, light meters are now available that can measure HSS such as the Sekonic L-858D. However, they’re very expensive. A Slovenian company called Lumu also makes a light meter that plugs into an iPhone to measures HSS. I saw these being demoed at a trade show and was very impressed with the results. They’re less expensive, but they currently work only with iPhones.
Provided you have the necessary equipment, the technique is quite easy. And it can give you a variety of results, so make sure you experiment with different amounts of exposure compensation.
Here are a few things to keep in mind while using this technique:
ISO. Generally speaking, you should keep your ISO as low as possible. Of course, if you have a particularly low-powered flash you may need to bring it up.
Flash Meters. Most flash meters can’t meter for HSS exposures. There are specialist meters that can, but be prepared to pay through the nose for them.
Daylight Conditions. This technique works in all sorts of lighting conditions, from direct midday sun to diffused light on a cloudy day. You’ll need a powerful light to overpower the sun on a bright day, but if you do the technique works really well.
Flashguns / Speedlights. Many flashguns have HSS functionality built in and are capable of great results. If you have a flashgun, consider using them for this technique.
Give it a try
Now that you’ve seen what can be accomplished with this relatively easy technique, I encourage you to get out and try it for yourself. And let us know how you went in the comments.