On this video photographer Matt Granger (aka ThatNikonGuy) looks at a very common topic which many photographers seems to have a hard time understanding – flash sync speed (as well as high speed sync).
As we explained on a previous video on this topic, you first need to understand how shutters work. Most camera shutters have two curtains that open and close. At speeds slower than 1/125th, or 1/60th depending on your camera, the first curtain open completely before the second curtain begins to close. At faster speeds the first curtain of the shutter opens and before it is completely open the second curtain starts to follow it and close. This means that there is no time that the sensor is open to light all at once. A small slit travels across the sensor exposing the frame it as it goes. If your strobe goes off during this time, it show a black bar at the bottom of the frame, basically the part of the image that was not exposed to the strobe flash.
So that sync speed is a mechanical limitation of most cameras. Theoretically cameras that use electronic shutters might be able to eliminate this problem completely and there are strobes that can pulse quickly and allow you to shoot a very fast shutter speeds – but for the most part this issue exist for most cameras and flashes today.
We have already looked at some of the basics of conventional flash sync on several videos in the past including “Understanding Flash Sync Speeds” with Karl Tylor and “Flash Sync Speed and Flash Duration” with Mark Wallace and more recently high speed sync and how it works with photographer Jay P. Morgan.