The Usefulness of High-Speed Sync
Among other things, high-speed sync lets you underexpose your backgrounds for dramatic images.
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.
This shot was taken without a flash and is all natural light. You can see the background shares a similar tonality to the subject, reducing the subject’s impact within the frame.
By intentionally underexposing the background with HSS, the subject now dominates the frame.
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).
Some studios strobes (such as the Pixapro Citi600) now come with HSS functionality built in.
- A trigger or some other means to fire your flash. (You’ll need a TTL-compatible trigger if you want to use TTL.)
If you want to use manual mode, a PC Sync cable will do the job. But for E-TTL you’ll need a compatible trigger. (The icon circled in red is the HSS icon.)
E-TTL Mode
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.
Switch your camera to ‘Aperture Priority‘ mode and choose the desired aperture. I’m fond of f/4 and f/5.6 for this technique, but it’s not a rule.
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.
Backgrounds that are already in shadow (such as the one in this photo) may only need one stop of underexposure.
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.
Backgrounds lit by direct sunlight (such as the one in this image) may need up to four stops of underexposure.
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.
Manual Mode
HSS is great for overpowering the sun. Here, three stops of underexposure controlled the appearance of the sun in the frame. Notice how dark the rest of frame (lit in broad daylight) appears.
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.
Adjusting the power in manual mode means dialing through all the increments on your flash. This isn’t a problem, but it’s harder than E-TTL.
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.
That’s It
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.
Though limited by your access to the equipment, this HSS technique is easy to employ and can result in bold, dramatic imagery.
Other Considerations
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.
This HSS technique works well in all lighting conditions. The image on the left was created in overcast conditions, while the image on the right was taken in direct sunlight.
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.
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