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Tips & Tutorials >> All Tips & Tutorials In Focus: The Basics of External Flash Photography- Part7

Capturing Portraits with Slow Sync Flash

Despite the extremely short flash duration, which is about several thousandths of a second, Canon's Speedlite is able to produce light strong enough to illuminate subjects. Therefore, when a shot is taken in low-light conditions, only the subject brightened by the flash light of the Speedlite will be captured in the image regardless of the shutter speed of the camera. This is the principle underlying the slow sync flash technique. (Reported by: Koji Ueda)

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Making Effective Use of Subject Blur with Slow Shutter & Flash Light

By combining flash light with a slow shutter speed, the subject can be expressed artistically by superimposing subject blur with a fleeting pose. The tip to using slow sync flash is to carry out the shoot at a location with little ambient light so that the background would not turn out too bright even at a slow shutter speed. Have the subject move his or her body to create motion blur, and overlap it with the image captured at the instant when the flash is fired. This is an effective technique for expressing the movement of the subject.

EOS 600D/ EF17-40mm f/4L USM/ Shutter-priority AE (0.4 sec., f/20, -1EV)/ ISO 100/ WB: Auto/ Speedlite 430EX II (E-TTL, exposure compensation: -1.7EV)


  • Use a slow shutter speed at a dimly-lit location in the shade
  • Fire the flash to "freeze" a fleeting movement

Shooting Condition

The shot was taken in the shade with the camera positioned 1.5m away from the subject. To create blur in the subject, I selected Shutter-priority AE and set the shutter speed to 0.4 second. The camera was mounted to a tripod, and the flash was fired directly at the subject.

Position of the subject, camera and Speedlite

A: Approx. 1.5m

Capturing Both Nightscape & Portrait Clearly

You can capture night portraits clearly by combining a slow shutter speed with a flash. A slow shutter speed helps to brighten the background, while the flash light illuminates the subject. To prevent camera shake when taking a handheld shot, secure a shutter speed that is equivalent to "1/focal length" seconds. In this example, I raised the ISO speed to 3200 to obtain a shutter speed of 1/30 second so that camera shake would not occur. As I was kneeling down on one knee for a low-angle shot, I placed the camera on the other knee as another measure to prevent camera shake. To ensure that focus is achieved precisely on the subject, I stopped down the aperture to f/4.5 while paying attention to the depth of field.

EOS 600D/ EF-S10-22mm f/3.5-4.5 USM/ Manual exposure (1/5sec., f/4.5, -0.7EV)/ ISO 800/ WB: Auto/ Speedlite 430EX II (E-TTL, Flash exposure compensation: -0.7EV)


  • Use a slow shutter speed to brighten the background
  • Use Speedlite to illuminate the subject
  • Raise the ISO speed to obtain a fast shutter speed

Shooting Condition

The camera was positioned at about 2m away from the subject with the nightscape of the city in the background. In order to include the full view of the high-rise buildings up to the topmost floor, I took a handheld shot from a low angle. Although it was necessary to slow down the shutter speed in order to produce a bright shot of the nightscape, doing so would have caused camera shake to occur, so I fired the Speedlite directly at the subject.

Position of the subject, camera and Speedlite

A: Approx. 2m

Steps for Using Slow Sync Flash

1. Select a slow shutter speed

Set the shutter speed to a slow setting. In a dimly-lit scene, the shutter speed slows down naturally to obtain the appropriate exposure. In a bright scene, however, the aperture needs to be stopped down to slow down the shutter speed so that proper exposure can be achieved. The Tv or M mode would be handy in this case.

2. Secure the camera

Even when you want to make good use of subject blur, camera shake should still be avoided. To prevent shake in a handheld shot, hold the camera firmly. If you have a tripod, make use of it wherever possible.

3. Select first curtain or second curtain

Select first-curtain or second-curtain synchronization by pressing the "Shutter curtain synchronization" button on the Speedlite. If this button is not available, select a synchronization mode using the setting menu on the camera.

4. Press the shutter button while paying attention to prevent camera shake

Press the shutter button while paying attention to prevent camera shake. If you are using a tripod, the use of the self-timer feature or remote shutter release is recommended.

Koji Ueda

Born in Hiroshima in 1982, Ueda started his career as an assistant for photographer Shinichi Hanawa. He later became a freelance photographer, and is now engaged in a wide range of work from magazines to commercials while shooting different cities and landscapes all around the world. He is also a writer and a lecturer at photography lectures and workshops.