[FIXED] Godox TT685c Flash - underexposed images in ETTL-II mode on Canon 6D


2 x 5D IV
Feb 26, 2017
I bought a little Godox TT685c speedlite and having some issues with underexposed images in ETTL-II mode on Canon 6D.

regardless of the camera mode used: AV, Tv, M, on camera flash or remotely triggered by X1T-C in radio slave ettl-II mode– makes no difference!
I tried many lenses and result is the same – underexposed images, badly. it almost as if pre-flash has never fired or camera has not enough time to analyse the pre-flash and set the exposure correctly.

If I bounce flash of the ceiling, underexposure even stronger. Shooting into soft box in ettl mode results in up to 3 stops of underexposure depending on how far the subject is located...

I found a workaround:
I push FEL (*) button each time prior to the shutter button release in order to force pre-flash and camera to record the correct exposure value... it works but...

Image with the same framing on tripod taken with FEL button pressed before taking the image is always perfectly exposed and without FEL button pressed can be up to 3 stops underexposed.

The necessity to push FEL button for every shot in ETTL-II mode drives me a bit uneasy :)
Godox TT685c firmware v.3.1, Canon 6D ( 1.1.7 firmware).
Camera works well with Canon, Godox ad360 II and Yongnuo speedlites in ETTL-II mode and exposure always applied correctly.
is this a known issue with Godox TT685c flash, firmware bug or the unit seems to be faulty?

[FIXED] it turns out to be the "user Issue". I failed to confirm that set of batteries I used were fully charged. and they were indeed at low charge level! but what is interesting - no low charge indicator came up on the speedlite screen. the rest is just logical. underexposure were the direct result of camera and speedlite incorrect ETTL interactions at such a low battery levels. forced preflash via FEL button set exposure levels correct though.
note to yourself: use the GODOX PB960 battery pack (as I should anyway) or swap rechargable AA batteries as soon as underexposed ETTL shots detected. pay close attention to the presence of the low charge indicator on the speedlite's LCD screen.


Dec 11, 2015
Re: Godox TT685c Flash - seriously underexposed images in ETTL-II mode on Canon 6D

Definitely worth replacing, because it sounds like a lot of unnecessary pain in the b@tt.


Jul 22, 2011
This semi similar problem is what i have using Godox trigger X1Tc ... TTL is so unreliable and always underexposing. When using YN622 TTL is spot on.

Doesnt matter which flashes I use. I suspect its TTL interpretation of Godox.