90D: High Speed Synch flash ?

[Casey Cheung]

Is there a setting to enable shooting in high speed synch flash mode? I know the X synch speed is 1/200th sec, but I want to shoot in outdoor sun at 1/8000th sec using either my Godox 685 or Godox AD200Pro flashes. When I change the shutter speed to 1/8000th sec on the camera body and fire a flash, the 90D body automatically changes the shutter speed down to 1/250th sec...without my permission, LOL! I went through all the layers of menus but couldn't find anything. Thanks!

 

[DavidArmenPhoto]

If the flash supports HSS, it will be one of the sync modes. For example, the options should be Front Curtain Sync, Rear Curtain Sync, or High Speed Sync.

Right now, your setting is most likely the default Front Curtain Sync which is 1/250th in most newer cameras.

 

[MitchAlsup]

Is there a setting to enable shooting in high speed synch flash mode? I know the X synch speed is 1/200th sec,

The synch speed is the fastest shutter speed where the shutter is fully open. In order to illuminate a sceen with a flash, the shutter has to be fully open.

but I want to shoot in outdoor sun at 1/8000th sec

At 1/8000 second shutter, both the top and bottom curtains are moving at the same time, enabling a sliver of light across the sensor through at a time. The traversal rate of the shutter is (you guessed it) 1/200 second, so to get 1/8000 effective shutter rates (40× faster), the shutter is open 0.0236" (0.0147" cropped), whereas if the shutter speed was 1/200 second, the top of the shutter moves 24mm (15mm) before the bottom of the shutter begins to move.

using either my Godox 685 or Godox AD200Pro flashes. When I change the shutter speed to 1/8000th sec on the camera body and fire a flash, the 90D body automatically changes the shutter speed down to 1/250th sec...without my permission, LOL! I went through all the layers of menus but couldn't find anything. Thanks!