High speed sync is an essential tool for creating professional-looking portraits on location and in the studio. Wedding pros as well as fashion and beauty shooters in particular use it to dial down the illumination on a brightly-lit background and light the subject with their flash. It’s the key to creating a balanced-looking photograph.
Your camera has a sync speed that’s typically around 1/160-sec. - 1/250-sec. On the Sony a7R II, for example, it’s 1/250-sec. On cameras with a mechanical focal plane shutter, it’s the fastest shutter speed at which the entire frame is exposed to light. If you shoot faster than sync speed with a mechanical shutter camera, you’ll see a dark area in the frame where the shutter hadn’t fully opened or had already started to close when the flash fired. With mirrorless cameras that have electronic shutters an analogous phenomenon is happening. The sync speed is the fastest shutter speed at which the entire sensor is recording exposure.
The problem with the sync speed is that it doesn’t give you a lot of latitude for balancing a bright background. For example, consider a typical wedding situation when you’re photographing the bride against in late afternoon sun you want to have her backlit. You’d typically want to light her with flash, but you also want to dial down the background to create that rich, balanced look. If you shoot at the sync speed, your only tool left is the aperture and it’s possible that even f/22 wouldn’t be sufficient. Plus you can get sharpness-killing diffraction and you need a whole lot of light from the flash when you shoot at a very small aperture.
Enter high speed sync. If your camera and flash can use high speed sync, you regain the shutter speed as a control to bring down the background. Instead of being limited to 1/250-sec. you can push the shutter to 1/2000-sec or more and shoot at the lens’ sweetspot of f/8 or so to expose the background beautifully while still getting fully-exposed flash illumination on your bride.
How does this work? When set to high speed sync in the camera and flash, the flash actually fires multiple times as the sensor (in the case of Sony mirrorless cameras) is being exposed. Imagine a narrow slit moving across the sensor from top to bottom, exposing the photosites as it goes. Let’s say the slit is 100 pixels tall. Every time the slit exposes a 100 new rows the flash fires, thereby exposing the entire frame in multiple flashes. And it works beautifully.
Not every flash is capable of high speed sync. In the Sony system, the HVL-F60M, HVL-F43M and HVL-F32M can do it. All of these flashes are part of the Sony Lens & Accessory Event which gets you special discounts when you buy an eligible lens along with accessories.
To see a good example of high speed sync in action, check out this video by Sony Artisan Jason Lanier. He shows how he uses high speed sync with his α7R II and a Sony HVL-F60M for a bridal shoot in Hawaii. In the video Lanier is using the flash off camera with a Pixel Kings wireless trigger. The new Sony TTL + HSS Wireless Flash Control System is expected to be available at retailers this spring.
In these frames from the video notice how harsh the light is and how blown out ths blue sky and clouds are versus how balanced and rich the photo looks.
During the Lens & Accessory Event, the HVL-60M is included in 2 of Sony’s recommended bundles, the Perfect Portraits and Flawless Wedding bundles. The HVL-32M is part of the Travel recommended bundle.