>>2840522Sure no problem. The way your shutter works at fast shutter speeds is not the same as the way it works at slower shutter speeds.
Your flash doesn't light the scene for the whole exposure. It pops very very quickly, and then goes dark. Most flash duration is in the realm of 1/10,000th of a second. That's why in a totally dark room, you can set up a 1 minute exposure and in the middle, pop your flash off, and at the end, your scene will look super sharp with no motion blur.
Below 1/250th, the first curtain opens, and exposes the whole scene to light. 1/250th of a second later, the second curtain follows it and closes off the sensor. So between those two curtains firing, your flash goes off, and the bright scene is captured by the sensor.
For faster shutter speeds, doing it that way would put a lot of stress on the shutter mechanism because it would have to move so fast. So in stead, what happens is this:
The first curtain fires, and starts to expose the sensor. Before it makes it all the way to the bottom of the sensor, the second curtain fires and starts to follow it. This means that at 1/500th, when the first curtain is still covering the bottom 1/4 of the sensor, the second curtain is following it and starting to cover the top of the sensor.
At something like 1/4000th, there's only a tiny slit of the sensor exposed at any time. The first shutter curtain fires and almost instantly after it, the second is firing too.
So since the whole sensor isn't exposed to the scene at once, your flash's super quick duration only happens while a part of the sensor is exposed.
It's sort of tough to explain in words, so ask more questions if I've been unclear.
