HSS not working with ST-E3-RT and 600EX-RT and 5ds

[mathew_z]

Hello

I cant get HSS to work. Shots are very dark.

The lightnig bolt H is on for both the flash and transmitter.

I'm using a canon 5ds camera set to manual, st-e3-rt transmitter and 600ex-rt is set to ETTL (but it doesnt work in M either) 

Any suggestion are helpful

Thanks! 

[diverhank]

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@mathew_zwrote:

Hello

I cant get HSS to work. Shots are very dark.

The lightnig bolt H is on for both the flash and transmitter.

I'm using a canon 5ds camera set to manual, st-e3-rt transmitter and 600ex-rt is set to ETTL (but it doesnt work in M either) 

Any suggestion are helpful

Thanks! 

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Out of curiosity, how do you know that HSS doesn't work?  The fact that your shots are dark doesn't necessarily mean that HSS doesn't work. It's possible the flash simply has not enough power to light up the scene.  It's also possible that the camera/flash read the light requirement wrong.  Have you tried cranking up the flash exposure compensation?  There should be some changes to the brightness there.  Have you tried the combo with speed less than 1/250?  Are the pictures correctly exposed or are they still dark?

[mathew_z]

The flash is in a small room and there should be more than enough power. With the flash set to ETTL the exposure should be acurate, right?  NO changes when adjusting FEC. WIth HSS off the flash exposure is correct (daylight is over exposed) 

[PLee · Accepted solution]

High speed sync will reduce the power output of your flash. If you feel that your flash exposure is already too dark with it on, then you should really try to turn it off. If it is still too dark and boosting FEC doesn't seem to help, then open up your aperture or increase your ISO depending on what you are trying to get done creatively.

If you are still having trouble, then you need to post the exposure settings and give a better description about what you are trying to accomplish.