sync speed question

[goodoneian]

around 2 weeks ago i picked up a pair of cybersyncs and an ab800. so far i've really enjoyed using them, but there's one thing i don't understand. i can now sync my camera at 1/320th of a second at any power with the ab800 while using the cybersyncs. is this because i have high speed sync enabled on my d300? although i'm quite glad i can do this i'm just curious as to what makes it possible

 

[Overread]

from my understandings of this it allows a faster shooting speed, but the power output of the flash will be less. That means that it won't have the range that it would normally have and you might encounter problems if the flash is to be the main light source if the main subject is also far off.
For closer work or where flash is being used for fill it won't be a problem much of the time - though I have read that if your shutter speeds get very fast you can end up catching the shutter movement in the shot (you get black bars which is the shutter closing/opening) though I have no idea at what speeds this starts to become a problem

 

[JerryPH]

Actually, you can come close to it becuase the AB800 has a very short pulse duration and the D300 has a native 1/320th sync speed. However, I bet if you take a close look at your pics, you *will* have the beginnings of a dark area in the picture. Put the camera on a stand, take 2 shots of the EXACT same white wall and compare the shots... you will find that the one at 1/320th has a bit more black across one of the sides. I did this with an AB1600 and my D700... it was there (using both my modded Cactus and PWII's).

The only time you will get perfect 1/320th sync speeds is with the new PocketWizards using HyperSync or when using all Nikon flashes.

 

[Garbz]

There is always a tiny safety margin for syncing. No electronics are perfect, so actual sync speed will be a tiny bit higher than 1/250th

 

[Gailpetersen]

You can also get inconsistent exposures as monolights often take longer to reach peak output than a camera strobe requires. With some monolights a shutter speed of 1/160 or slower is needed to get all the light from the strobe to the camera's sensor regardless of the sync speed of the electronics that trigger the flash.

 

[JerryPH]

With some monolights a shutter speed of 1/160 or slower is needed to get all the light from the strobe to the camera's sensor regardless of the sync speed of the electronics that trigger the flash.

Those would have to be some very low quality or old monolights. Most modern ones have a T.5 (flash duration) in the thousandths of a second.