1/800 flash sync not working

[rmtz00]

One of the many advantages of the Hasselblad H system is the fact you can have 1/800 shutter time to shoot with flash. I tried it in my studio and it doesn't seem to work. 1/150 works fine, like it should, but from about 1/200 to 1/800 the image gets darker the shorter the shutter time. This is weird, because shutter time should have no effect on the image's brightness, only the aperture does this. What could be the problem.
I shoot with a Bowens flash-set that can sync 1/1200, so it should be fine. Also I use the Pocketwizard PlusX. What do I do wrong?

[jerome_m]

Try your flash with a direct sync cable and see if you have the same problem. If you don't, your wireless controller is too slow. If you do, your flash is too slow.

[NickT]

Yes. What Jerome said. Some flash units have really long flash durations meaning that fast shutter speeds will reduce the exposure (even though in theory it shouldn't).

Nick-T

[rmtz00]

Thanks for the quick replies! I've been checking several things today and came to a solution. First of all the True Exposure feature was on. When I put it off images suddenly looked fine up to 1/400, more or less. When I hooked a sync cable up (instead of the Pocketwizard remote) I could achieve sync times of 1/800.