After taking so many macro shots, I think that I really love my d40 which allows me to take 1/4000s with external flash and no black out image.

Regards
Leigh

Sync speed can vary with same maker flash units for your camera.

On my Canon cameras, sync with studio strobes is 1/200th.

But if I use my Canon flash unit with high speed sync turned on, I can sync up into 1/2000 range as the camera and flash unit are made to work together.

It really depends on the subject and ambient light. Flash illumination falls off per inverse square law so background may not be sufficiently illuminated if too far relative to subject. Often you can choose a slow shutter speed to pick up better background exposure and use the flash exposure to freeze the subject.