Special Flash Effects Second-curtain sync for a natural-looking, moving subject. With normal flash, the flash fires when the shutter curtains are fully open. This is called first-curtain sync. Since there is no time lag, it makes it easier to capture the decisive moment. However in this case, an unnatural effect may result with a moving subject as shown in the sample Photo A. The person appears after the trail of the fireworks. By selecting the second-curtain sync mode either on the EOS camera (custom function) or on the EX Speedlite (availability varies from model to model), the flash fires right before the shutter curtain closes. As shown in Photo B, second-curtain sync and a slow sync speed makes the picture look more natural with the fireworks trail following the child instead. Stroboscopic flash Stroboscopic flash to reveal movement Stroboscopic flash is a series of flashes fired successively within a short period of time. With stroboscopic flash, muliple images of the moving subject appear in the photograph. The 550EX's stroboscopic flash frequency can be set from 1 to 199 Hz (the firing interval within 1 sec.). Set the flash frequency, number of flashes, and sync speed suiting the time period of the subject's movement. The photo above was shot with the stroboscopic flash set to 2 Hz, number of flashes to 5 and the shutter speed to 3 sec. to capture Eleonora bringing a pizza. << Back to Main . 1 . 2 . 3 . 4 . 5 . 6 . 7 . 8 .