Slow sync is a photographic flash technique that combines flash with a slow shutter speed. When shooting in dim light or at night, using a fast shutter speed often produces an image where the subject is brightly illuminated by the flash while the background remains dark. By using a slower shutter speed with the flash, slow sync allows ambient light to register, revealing more background details and creating a balanced, natural-looking exposure.
This technique is particularly useful for night photography, low-light portraits, and creative lighting effects where both the subject and environment need to be visible.