Fastest Sync Speed for Alien Bees Studio Lights and 10D

In consulting my manual it states that the fastest shutter speed is 1/60 or slower. I notice that it states for non-canon compact flash it can go up to 1/200 and slower. Can someone explain why this is? Just received my lights and getting ready to stay up entirely too late to play.

What it says is that the 10D can synch to compact electronic flash at 1/200 or slower, or large studio lights at 1/60 or slower.

The reason is that compact flashes (i.e., those with guide numbers under 200 or so), have a maximum flash duration of perhaps 1/500 or even less. Thus, all that is required is that the shutter is all the way open when the flash fires. That's 1/200.

But some big studio lights dump LOTS more juice into the flash tube, resulting in much longer flash duration. My Speedotron, for example, when all 1600 ws is going into one head, has a guide number of something like 540 and a flash duration of around 1/125 or 1/200 if I'm remembering correctly. Bigger studio rigs are even longer. Canon can't know how much time your flash system consumes, so I suspect they suggest 1/60 to be safe.

Plus, if you use studio lights, first-curtain synch is probably the right thing to do, because second-curtain synch depends on a short flash duration.

I don't know about the Alien Bees since I haven't been in the market for studio lights in a long time, but they may say what their maximum-power flash duration is.

Rick "who has used the Speedotron with the 10D at 1/200 with no problem--but not with all power going into one head" Denney

Alien Bees durations are printed on the website and the manuals. (The longest is 1/1600th of a second.) I use them at 1/200th without any problems.

My 10D can sync at 1/250 - I'm sure all the others will as well.

Thanks all, well I was away from the Forum snapping pictures at 60. I'll try again tomorrow at 200 to see how things turn out. Thanks for the info!

Jim

It will synch with the nose flash at 1/250, but not with an external flash (even the 550 EX). When my 550 is on the camera, the camera will not allow me to set speeds faster than 1/200.

Rick "who notes that with an EX flash in very limited circumstances, the 10D can synch at much higher speeds than 1/250, but who hasn't found much practical use for that feature--yet" Denney