I think I have a basic understanding of how HSS works, maybe not ;). My question, with the same strobe power setting and in manual mode, does the strobe exposure effectively attenuate more and more as the shutter speed is increased or is the attenuation the same. Say we go from 1/200 max X-sync speed to HSS at 1/250 and 1/500 and then to 1/1000?

Yes, you will experience decreased strobe power at faster shutter speeds. Here's a quick test that I did - shooting a white wall from about two feet away, single Retra Pro on full power ISO 100, f/36 to exaggerate the effect. The 1/160s shot is in normal mode, the rest are in HSS.

 

Interesting. The difference between 1/160 and 1/250 is surprising. Is that possibly due to ambient light when you did the test? I would have thought that all of the flash pulses would still be contained within an interval of 1/250 second? 

Edited April 1Apr 1 by Nemrod

That's the difference between regular flash and HSS. The flickering mode of HSS produces significant reduction in flash power by itself, before higher shutter speeds bleed it further. 

Thanks, now I understand, I think. Thanks.