High speed sync

[Firotechnics]

Can someone explain to me exactly how high speed sync works

[SYS]

I'm no expert on this topic, but I'll take a shot at it...

Each DSLR camera comes with the maximum X-sync speed. I believe your 30D is 1/250 like my 40D, but I don't know what it is with your 5DII. The max sync speed is the speed at which the flash can capture the full image when the pair of moving curtains (shutter) inside the camera is fully open.

In order to allow the flash to work in higher speed than the maximum sync speed, the camera engineers came up with the flash throwing continuous pulse of light through the curtains' slit throughout their movement. That in essence is what the high speed sync is about. Because of weak pulses of light, typically the high speed sync is used as "fill" in outdoor shooting when the proper exposure requires the speed higher than that of the camera's max sync speed, 1/250th in your 30D's case.

[Mark1]

It simply fires the flash many times in extreeme succession. It has to do this because with shutter speeds faster than 1/250 the second shutter begins to close before the first is completely open. If it was to fire only once the area that was covered by one of the shutters will not be exposed properly. So HSS kinda makes it a constant light for as long as needed to make an even exposure.

[zeva]

OOO! good explanation i did not know that! lol

[dann22]

That answers my question. I got to practice at a coworkers wedding the weekend before last (she had a paid photog there)and when shooting outside in the bright sun I decided to use the flash to kill some of the harsh shadows in the face. It was so bright, it blew out half of the black tux. Later after thinking about it I remembered that the flash wont let the shutter go above 200-250 depending on which camera.

[Curtis N]

http://web.canon.jp/imaging/flashwork/ettl2/high/index.html

[calraisin]

Another great link on HSS: http://pixsylated.com/2008/11/simple-truths-about-high-speed-sync/

[canonnoob]

What about when shooting off camera?

[Curtis N]

What about when shooting off camera?The only way to get HSS off-camera is to use the Canon wireless flash system or an extended Off Camera Shoe Cord.

[tsw910]

not if you're using the latest fro Radio Popper .. than HSS can be used and TTL

[mrgooch]

Just to clarify. If I am using off camera with cybersyncs I won't be able to use high speed sync.

[Familiaphoto]

Correct, no HSS with cybersyncs.