Iplus no matter how you try to trick the camera/flash, most flashes have a max sync of 60 or 125, unless you get a higher end flash that has high speed sync..
Here's why. We tend to think of the shutter as being open or closed. If we take a shot with a shutter speed of 1/125s, the shutter is closed, it opens for 1/125 seconds, and then it is closed again. That's not
exactly how it works.
The shutter consists of two "curtains". When the first curtain pulls away, incoming light hits your sensor. When the seocnd curtain comes down, the sensor is blocked again. So far, that sounds pretty normal.
The trick is when you take picture with high shutter speeds. If you take a shot at 1/500s, your camera's shutter just isn't fast enough. The exposure starts off normally enough, with the first curtain racing across to let light hit the sensor. However, before it gets to the other side of the sensor, the second curtain starts coming along behind it blocking the sensor. At no point in time is the entire sensor exposed. Instead, there is a little moving gap between the two curtains that sweeps across the sensor. The net effect is that no part of the sensor is open for more than 1/500 of a second, but the entire process takes much longer (probably about 1/200 of a second).
When you set your shutter speed faster still, say 1/4000s, the shutters don't move any faster. The gap between then just gets smaller. The time between when the first curtain and the second curtain passes is now only 1/4000s, but it still takes 1/200s for that gap to make its way across the sensor.
There are two important lessons to take away from that. First, using really fast shutter speeds to freeze motion doesn't really work quite the way might think it does. That's because while the exposure might be for 1/4000s and no one part of the picture was exposed for any longer, it still took 1/200 for the entire picture to be exposed.
Second, the normal flash sync speed of your camera is determined by the fastest shutter speed at which the entire sensor is exposed. For most cameras, that seems to be somewhere around 1/125 to 1/500, depending on the camera model. The flash duration is usually extremely fast (from about 1/1000s for a Canon 580EX at full power to about 1/35,000s for the same flash at 1/128 power). It just has to happen during the time between when the first curtain has revealed the sensor and before the second curtain has started to cover it.
Now your probably thinking that I'm an idiot because you've seen flashes capable of operating at much higher speed sync modes. That's true (well, hopefully not the idiot part, just the part about flashes working at higher speed modes). The trick is that they work differently in high speed sync mode. In that mode, the flash starts just before the first curtain starts to reveal the sensor and keeps shining until just after the second curtain closes the last bit of the sensor. So while the two curtains are racing across your sensor for your 1/4000s shot, which I've told you takes about 1/200s to take, the flash is shining for the whole 1/200s.
There are a couple of good points to take away from that as well. First, if you were using a high shutter speed to freeze motion, you'd have done better with the 1/200s shutter speed and 1/10,000s (or whatever it worked out to be) flash duration than you would with a 1/4,000s shutter speed and a 1/200s total exposure duration. That assumes, of course, that your flash was your primary source of light.
Second, running your flash in high speed sync mode all the time comes at a price. Because the flash duration is longer for each shot, you munch through batteries faster and your recharge times are longer. I've never actually tested that, but it seems like it must be the case.
To be honest, all of this is based on observation, various ruminations, conversations with friends that may or may not know what they are talking about, and a few odd references. If you think I'm wrong, don't be cowed by any sense that I must know sometime. Feel free to correct me or disagree.
That is why I used the fully auto mode in the first place. I knew that my creative juices had taken a backseat to the Bud Light demons.
The flash may appear to be on continuously but actually it is repeatedly firing fast enough so it can cover the entire exposure without missing a part. Consider, if the shutter is set for 1/800 but it actually moves at 1/200 then it would be a slit 25% of the total shutter opening. In that case four flashes timed properly would illuminate the entire image as far as the sensor is concerned. That's some difficult timing but if we had many more than four flashes they would not even have to be timed properly. It's no problem (electronically anyway)firing the flash 10,000 or more times a second, that's 50 flashes per shutter actuation!
although i could probably master that one.
I think that the reason for this was the lower, all white ceilings that I was bouncing the flash off of. I really really concentrated on what I was doing at this wedding, but still, I screwed up a large portion of my shooting by trying to figure out how I could push a faster shutter speed from my camera. Well, after about an hour of giving up, I realized that my ISO was set at 100! I never even thought of ISO! Why, why, why can't I remember all the things that go into this hobby? 
Anyways, those photos were somewhat saved by the fact that I shot RAW and was able to PP them enough to make them look good. There is blur in some, of course, but the biggest problem was underexposure and it was somewhat easily correctable. 
