What is flash sync speed?

• A. The maximum shutter speed at which the flash can evenly expose the frame
• B. The minimum shutter speed recommended when using flash
• C. The color temperature of the flash
• D. The power setting of the flash

Answer: (A)

Flash sync speed is the fastest shutter speed at which the flash can evenly illuminate the entire frame. In a camera with a typical focal-plane shutter, the shutter curtains move across the sensor, and the flash must fire while the sensor is fully exposed. If you shoot faster than the sync speed, the flash fires while the curtains are still moving, which can create a dark band or partial exposure because part of the frame isn’t exposed when the flash fires. That’s why you stay at or below the sync speed to get a complete, evenly lit image. Some cameras offer High-Speed Sync to use faster speeds with flash, but that changes how the flash outputs light and can reduce range and efficiency. The other options describe color temperature (the warmth of the light), a recommended minimum shutter speed for using flash (not about full-frame synchronization), and the flash’s power setting (brightness), none of which define the timing needed for a full-frame flash exposure.