Speedlite 430EX II & Speedlite 600EX-RT underexposed.

[rrnkp]

Hi,   I have 430 EXII and a 600 EX. On my t6i both flashes set to E TTL  work properly in all modes  auto, program and manual, with the exception of the exposure confirmation lite on the 600 EX. It does not illuminate.

Now the weird part when I use either flash,E TtTL, on the the 70d both flash are under exposing but the exposure confirmation light flashes on the 600 EX, meaning it was properly exposed. Either I have to go +3 on exposure compensation or manual 1/1 for the pics to come out properly. This occurs in all modes auto, program and manual.

I'm photographing dimly lit parking lots/ streets at all distances. Both cameras have 18-135 Canon lens. 
I’ve tried the Canon 18-55 and 50mm f1.8 on the 70d still under exposed.  
 Any ideas on what’s going on?

[rs-eos]

I'm trying to follow... are you saying you have two camers (T6i and a 70D) and with the same exact two flashes, you're seeing differences?

First thing to rule out... are the flashes in the same positions in both of your scenarios?

Also, is there a possibility that during the setup with 70D, that one of the flashes was able to "see" the other one?  When all flashes are in E-TTL and they "see" each other, that will affect the amount of power chosen for the flashes.

[deebatman316]

First of all how are you using these speedlites. Are the speedlites fully recharged when this happens. To clarify you are using the 600EX not the 600EX-RT or 600EX II-RT. Please clarify each issue with BOTH cameras. Its hard to follow along how you're describing the problem.

[Anonymous]

Is it possible that you have external flash settings (flash exposure compensation) set in the 70D that might be overriding the FEC in the flashes themselves?

[deebatman316]

When FEC is set on the speedlite it overrides the camera body's setting. Regardless of which one has more or less FEC dialed in. Also FEC doesn't work in Full Auto so there are more things going on. We need to know the "big picture".

[Anonymous]

I tested with my 5D IV and a 600EX-RT, and if the flash has zero FEC, and the camera has -1 set in the external flash menu, the camera will change the flash FEC to -1 with a half press of the shutter button. So, I disagree that that could not happen. The camera can override the flash FEC,

[deebatman316]

Just as I said. If the speedlite already has FEC dialed in (ie NOT set to 0 FEC) and you set FEC in the camera. The speedlite overrides the camera body's FEC. Also that's if the speedlite is set to 0 FEC and you add for instance +1 FEC. The camera body's FEC will be applied. If there isn't already FEC dialed in on the speedlite. If the speedlite has +1 FEC dialed in and you dial in -2 FEC in the camera the speedlite's FEC is used and the camera's is ignored it's in the manual. 

[Anonymous]

But if he doesn't realize that he has FEC set in the 70D camera, it would explain his problem with the 70D. His T6i may have zero FEC set in the camera, so it works as expected. See my point?

[deebatman316]

He said it was happening in Full Auto mode too. FEC can't be used in Full Auto and the speedlite is locked. So all settings return to default and E-TTL can ONLY be used. Try your camera and speedlite out in Full Auto mode. You can't change speedlite settings it will report "Locked".

[Anonymous]

How about we let the OP decide if my advice is good or not. There is no need for you to criticize someone else's advice. My advice is free and worth every penny!