When you use a flash, the shutter speed is not that important. Since the flash fires all its power in 1/1000th sec or less, it is not important whether your shutter speed is 1/200th second, or 1/100th, or 1/4 second. Only the ambient light will be affected; not the flash part.
Take this, from a Goldcorp goldmine I shot earlier this year in Timmins, Ontario:
3200 ISO, f/4, and 1/4 second. Handheld.
Why so long? Because I wanted the light at the end of the tunnel to look like, well, the light at the end of the tunnel. And I needed f/4 for depth of field, hence 3200 ISO and 1/4 second.
But Michael, things will be blurry!
Not if they are lit by the flash. 1/1000th sec is 1/1000th sec! And if they are also lit by a little ambient light, then a little ghosting will appear, mainly in the moving parts:
But that is still better than not having any background light. So I shot the goldmine at slow shutter speed, and you should feel free to try the same. Here I did it to capture the hard hat lights:
Use a wider lens, and go slow, even very slow, any time you are using flash and it’s mainly flash lighting the important bits!
If you want to freeze water drops or something similar, it works better to use sync speed or a little slower, relying on the flash to stop motion, than to use a higher speed and High Speed Sync. Using High Speed Sync gives blur because of the multiple flashes.
And what’s more : low power for freezing water drops. The reason I have outlined before: the lower the flash power,t he faster the flash.