Is there a limit to High-speed Sync?

[rgrebby]

On the Sigma 530 super there is an option to turn high speed sync on.
From what I can tell it lets you have a high shutter speed in order to knock out the ambient light and it does this by firing loads of flashes at once and hoping that it gets one when your shutter is open.

Am I right?

Anyway is there a limit to how high a shutter speed you can go? Also are there any drawbacks like massive battery consumption and possible over heating?

 

[HoppyUK]

I don't know about the Sigma, but I'm pretty sure it's similar to the Canon 580EX and other guns with high speed sync.

For the Canon, it works by strobing the flash very rapidly, at 40,000-50,000 per sec - yes you read that right. It's the same facility that is used to code the pre-flash with all the exposure data in E-TTL mode. The flash is effectively turned into continuous light and it works very well indeed, at any shutter speed.

However, unsurprisingly it rags the flash to death and Canon warns of overheating if you overdo it, plus distance range is reduced, recycling is slower and it eats batteries.

But it gets over the problems of high-speed sync with focal plane shutters in one leap and is just what you need for short range fill-flash in bright sun.

 

[rgrebby]

Great. Just wish I could use it with wireless