Sync speed

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Sync speed is the speed at which the camera's focal plane shutter is able to synchronise with flashguns or studio strobes. Generally speaking, a camera will have a maximum sync speed, typically 1/60 for consumer equipment, and 1/250 for pro equipment. Use of a higher camera shutter speed will cause black bands on the image, because the shutter is only partially open when the flash fires. Any speed lower than the maximum sync speed will, however, work properly.

The actual duration of the flash is typically 1/2500, which becomes the effective speed of capture, except when using fill flash in bright ambient light.

Normally, the flash fires at the earliest moment that the shutter is fully open. With a moving object in ambient light, this gives the impression that the object is moving backwards, because the blur trail seems to end in the fixed, bright point captured by the flash. Many Nikon cameras are able to overcome this using rear curtain sync, which, when selected, causes the flash to fire at the last moment that the shutter is fully open.