Rear curtain sync, also called second curtain sync, is a flash technique where the flash fires at the end of the exposure rather than at the beginning. This timing difference creates distinctly different motion blur effects compared to standard front curtain sync, making it particularly valuable for photographing moving subjects with flash in creative ways.
In standard front curtain sync (the default on most cameras), the flash fires as soon as the shutter opens, freezing the subject immediately and then recording any motion blur that occurs during the rest of the exposure. With rear curtain sync, the sensor records motion blur first, and then the flash fires just before the shutter closes, freezing the subject in its final position. This creates motion blur trails that follow behind the subject rather than appearing in front of it.
Why Rear Curtain Sync Matters
The practical difference becomes obvious when photographing movement. Imagine photographing a moving car with a slow shutter speed. With front curtain sync, the flash freezes the car at the beginning of the exposure, and then motion blur trails appear in front of the car—creating the unnatural appearance of motion streaks leading the subject. Rear curtain sync reverses this effect, creating motion blur trails that follow behind the subject with the car frozen in its final position, which appears natural to our perception of movement.
Practical Applications
Rear curtain sync excels for dance photography, where you can show the blur of movement while keeping the dancer sharp in their final pose. Wedding photographers use it to create dramatic first dance images, capturing the twirl of a dress while keeping faces sharp. For example, photographing a spinning dancer at 1/4 second with rear curtain sync creates beautiful motion streaks throughout the exposure, culminating in a perfectly sharp final image. Typical shutter speeds range from 1/15th to 1 second depending on the subject’s speed and desired effect.
This technique works equally well with on-camera flash or off-camera flash setups. When combined with intentional camera movement or panning, rear curtain sync creates especially dynamic results. The technique requires some ambient light to create the motion blur trails—in completely dark environments, there’s no ambient light to record motion. The key is balancing flash power with ambient exposure so the flash provides the sharp frozen element while the ambient light creates the motion blur.