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So what is flash sync speed?
It is the maximum shutter speed you can use to “sync” with a flash. An external flash is a flash that sits on the hot shoe of the camera or is remotely triggered off camera. An internal flash would be one that is built into the camera itself such as a small pop-up flash.
Why is there a limitation on shutter speed when using a flash?
The camera has a shutter that is basically like curtains that move over the image sensor. The front shutter starts to move and exposes the image sensor to light and then the back shutter follows and covers it up again. The faster the shutter speed, the faster these curtains move and for very fast shutter speeds it’s common that there isn’t a time when the whole image sensor is exposed to light all at once.
So, when you use a shutter speed faster than the flash sync speed, you end up with dark shadows across the image as if the flash had malfunctioned, but this just because the shutter is moving too quickly to allow the flash to be exposed to the entire sensor at once.
The sync speed is the fastest speed that allows the entire sensor to be exposed to the flash to…
