Slow sync flash photography: how to shoot portraits with movement

In this tutorial we show you how to combine a constant light source with an off-camera flashgun and waltz  your way into slow sync flash photography.

Capturing dance through stills photography can be a real challenge; the movement of a dancer has to be conveyed in a static image. Some photographers will photograph a dancer mid-leap, others will get the dancer to hold intricate poses. But there’s another way to capture dance: using slow sync flash photography.

What does slow sync flash photography mean? Well, it’s the simple act of using a long exposure, combined with a flash firing at either the beginning or end of the period when the shutter is open.

The long exposure allows ambient light to expose the scene, and the flash provides a momentary burst of light to freeze any motion. For our photo we worked with a professional dancer, but you could just use an enthusiastic friend running and leaping into the frame.

Depending on the power of your lights, your settings will vary. Our settings were f/10 at 4 secs and ISO200. This kept the depth of field nice and deep, maintaining good focus on the performer as he moved around the scene. The four seconds were all the dancer needed to complete his move, while ISO200 ensured that our images would be free of noise.

It’s best to shoot against a plain wall or black backdrop. Have your dancer stand in front of the backdrop, and position a flash to the right of the camera shooting into the scene, and a continuous light (or desk lamp) to the left, to provide the ambient light.

The key to this technique is to set so-called ‘rear-curtain sync’, which means the flash fires at the end of the exposure rather at the beginning. If your dancer is moving from left to right, this will result in an image with a blur of movement and colour on the left, and a crisp, sharp dancer at the end of the blur trail on the right.

SEE MORE: Flash photography made easy: how to use rear curtain flash for cool motion effects

How to set up your slow sync flash portrait

01 Fade to black
Put up a plain backdrop and turn on your continuous light. Keep your ISO at 200, and your shutter speed at roughly 4 secs. Experiment with the time, though, as what works will depend on how fast the dancer moves. An aperture of f/10 will give you a good depth of field.

SEE MORE: How to shoot outdoor portraits using flash

02 Take remote control
We set our camera on a tripod and used the Nikon WMU app on our smartphone to view the scene and trigger the shutter. Not all bodies have this connectivity – if yours doesn’t, you could use a remote shutter release or your camera’s self-timer to avoid camera shake.

SEE MORE: 3 photos made easier by a tripod and remote release

03 Go wireless
Put the flash on a light stand with a wireless receiver attached (we used a Pocketwizard Flex TT5). Put the wireless trigger on your camera. Aim the flash at the right-hand end of the frame, and the continuous light, floor lamp or desk lamp at the left-hand end.

SEE MORE: Best wireless flash trigger: 6 top options tested and rated

04 Raise the curtain
To set your camera to rear-curtain sync, press the flash button on your camera body and scroll the wheel until it displays: REAR and the flash symbol. Not all bodies are the same, so check your manual if you get stuck (you may find it’s in the menu on your camera).

SEE MORE: How to always get exposure right – your camera’s exposure settings explained

05 Strike a balance
You’ll need to balance the two lights (continuous and flash), so turn them on one at a time, starting with the continuous light. Once you’re happy with the effect of this ‘ambient’ light, turn it off and do the same with the flash, adjusting the power manually as needed.

SEE MORE: How to shoot portraits with continuous light sources

06 Get dancing!
Once you’re all set up, it’s time to get dancing. Have your dancer move from left to right across the frame, and try to time the exposure so that it starts when they are at the left of the frame, and ends when they get to the far right. You may need to experiment with shutter speed.

Final tip
There are two forms of curtain sync: front-curtain sync and rear-curtain sync. As its name suggests, with front-curtain sync the flash fires at the beginning of the exposure, then leaves the shutter open for however long you’ve set. With rear-curtain sync, the flash fires at the end of the exposure, just before the shutter closes. You may want to play with this at home and see how the results differ.

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