Flash sync speed

All cameras have a fastest recommended speed at which they synchronize with a flash. On most DSLRS and Z-series Nikons, the flash ‘sync speed’ is usually either 1/200 sec or 1/250 sec. This is governed by the time it takes for a focal plane shutter to move while revealing the sensor to the burst of flash. A focal plane shutter consists of two curtains, the first opens when you shoot an image, exposing the sensor. The second curtain then follows, moving across the sensor to block out light. At faster shutter speeds, the curtains can both be moving together, with the second curtain closing before the first has opened fully. If you choose a shutter speed faster than that of the sync speed limit, for example 1/500 sec, this does not give enough time for the shutter to open fully, so the sensor can’t fully see the instantaneous burst of flash light. The result is that you see the second curtain in your image, which will most likely be blocking part of the scene. You can get around this by using AUTO FP mode, which fires multiple bursts of flash through the duration of the exposure to evenly light the scene. We will look at this advanced technique in much more depth in Nikon Academy next issue, when we check out techniques for using off-camera flash.