High Speed Sync problem--

[jpharbour]

I have a question about high sync speed please. I've watched many video but I am misunderstanding something basic I guess. I have a canon 6D with a 600ex ii-rt. When I take a portrait at f4 and 1/200, the model is lit nicely, but the background is too bright. I want to darken the background, but as soon as i go into high speed sync, everything is darker, not just the background (say a 1/500 holding at f4). I thought the f stop regulated the light from the flash and that would keep the subject lit properly, while the shutter speed regulates the ambient light for the background. Why am I losing light to the subject in high sync flash? I am on manual mode. The 600 ex ii-rt does show high speed sync as does the camera. Thanks

 

[fundy]

My understanding is that both aperture and shutter control all the light from the scene.
So if you want brighter subject you would need to crank up the flash power - maybe you can try adding flash exposure compensation. As the light from the flash should affect the closer objects more (square law).

 

[Bebulamar]

High Speed Sync flash wastes a lot of flash power so much so I wouldn't not use it.

 

[table1349]

Flash Photography with Canon EOS Cameras - Part I.