Originally Posted by
Arthur Morris
Hi Michael, No probelma; we are here to help. You missed the fine print: High Speed Synch. In order to get your camera to fire at shutter speeds higher than your camera's synch speed, you need to set High Speed Synch on your flash. In the row of four buttons on the back of the flash, the third one, from left ot right, is the High Speed Synch/Rear Curtain button. Depress it once and the HIgh Speed Synch symbol (a lightening bolt in front of a small capital H) appears either to the right of the ETTL symbol or just above and to the left of the Manual Flash ratio, for example 1:1. Press it again and the Rear Curtain Synch symbol appears just above and on the left side of the distance range scale. Perss it again and neither symbol appears.
Once the High Speed Synch symbol appears, you will be able to set shutter speeds higher than the camera's synch speed. Here's how High Speed Synch works: If your camera's synch speed is 1/250 sec., and you set your shutter speed to 1/500 sec., then the flash has to fire twice during the exposure. And so on and so forth as you choose higher and higher shutter speeds. Heres the rub: the higher the shutter speed that you choose, the more the flash output is reduced. That is why I almost always set the flash to 1:1 in Manual Mode when do High Speed Synch flight flash; in effect, the flash is going nowhere at 1/2500 sec so you mazimize the flash output by setting 1:1 (full power) in Manual Mode.
I am going to copy this thread to Educational Resources and title it High Speed Synch. Thanks for asking a good question.