Eric Stoner
Eric Stoner

Eric's professional photographic career spans over 25 years specializing in portraits, weddings and commercial photography using everything from simple lighting to very complex.

Ultimate control of flash outdoors using High Speed Sync

December 10, 2013

One of my favorite tools in the camera bag is my Speedlite, but it can be frustrating in certain situations if you don’t know how to control it. For example, let’s say you’re photographing someone outside with the sun at their back and you want to use flash fill from the camera to brighten up the shadows. It’s certainly a reasonable request from your camera, right? More than likely, it came out looking like the photo below – washed out!

Frustrating, isn’t it? Having an understanding of how the flash system works will help. I’ll explain. Your camera has what’s called a maximum sync speed and it varies slightly depending on the camera you own. What this means is that you are not able to shoot with a Speedlite at shutter speeds over the listed maximum sync speed. For most Canon cameras, it’s either 1/200 sec. or 1/250 sec. The camera simply won’t let you do it if a Speedlite is mounted on the camera. If it did allow you to take a picture, it might look something like this:

A major portion of the frame would be blank and this is caused by the shutter blocking the part of the sensor during the exposure. DSLR cameras have two shutter curtains that follow each other down the plane of the sensor, therefore not exposing the entire sensor at the exact same moment. Maximum sync speed exists to give time for the entire “pop” of the flash to be recorded over the entire sensor as the two shutter curtains travel across the image area. Canon has included this “fail-safe” of not letting the camera shoot faster than the maximum sync speed when it “sees” a Speedlite attached.

You may say to me, “Eric, I shoot with a flash outdoors on sunny days all the time! What are you talking about?” Yes that’s true and you probably were left with images sharp from foreground to background like this one:

It’s a nice shot of my son, but the background is pretty sharp and causes the viewer’s eye to wander all over the picture. There are too many details to look at, pulling your eye away from the main subject. This shot was taken at f/16 with a EF 70-200mm f/4L USM lens, using ETTL flash (Automatic) but we do have proper exposure. Ideally, we’d like to use a much wider aperture like f/4 or 2.8 to allow for shallow depth of field, thus bluring out the background and forcing your eye to look at the subject. Being at f/2.8 just won’t work at the 1/200 sec. maximum sync speed of my EOS 5D Mark III on a sunny day, as shown in the first photo. It’s way overexposed or washed out.

High Speed Sync to the rescue!

There’s a tool on the Speedlite called “High Speed Sync” that allows the user to shoot with flash at any shutter speed the camera has available. It’s a great tool that helps you shoot at 1/8000 sec. if you need to!

This photo was shot in the same place as the last one, but I used high speed sync and was able to go beyond a shutter speed of 1/200 sec. and shot it at 1/1500sec. at f/2.8. Notice the background is much softer. There are no award winning shots here, for sure, but I’m simply showing you the concept!

Now I can take this concept a bit further and ramp my shutter speed all the way up to 1/8000 sec. Do you see the difference in the photo below? The background is much darker, almost looking like night time. I’m essentially overpowering the sun with flash by using a fast shutter speed, yet the exposure on my son’s skin tone is the same.

Below are pictures of the top two Canon Speedlites, the Speedlite 600EX-RT and Speedlite 430EX II, and how to access this feature.


What high speed sync essentially does is allow us to shoot at wide open apertures and high shutter speeds in a fully lit area using a Canon Speedlite. The one issue with this technology is that it greatly diminishes the power output. Rather than one big flash “pop,” it pulses at approximately 30,000 times per second to ensure the flash is firing at every point as the shutter travels across the imaging plane. The other item you should know is that the more you increase the shutter speed, the less power output the Speedlite will be able to produce, so keep them close to your subject. To boost power, I often gang up two or three Speedlites on a rig, like this one below from Wescott. Sometimes, if I need a lot of power, I’ll use six all together but that’s rare.

There’s another benefit to high speed sync that you might have already thought about, given the name of this feature, and that is fast action. At maximum sync speed of 1/200 sec., don’t expect to freeze fast moving subjects like the bat movement seen in the example below.

I took a second photo at 1/6000 sec. and the bat is completely frozen.

To sum it up, high speed sync is a powerfull tool, especially with the Speedlite 600EX-RT because of its radio based wireless technology. Having the ability to shoot off-camera flash at wide open apertures when the sun is blazing affords any photographer the benefit of shooting whenever they want to instead of waiting for the light to be right. Speedlites MAKE THE LIGHT RIGHT!

I hope this shed some “lite” on the subject of high speed sync!

Until next time . . .

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