Godox AD600 and TT685 - Significantly Underexposed in TTL - Suggestions?

I have been unhappy with the exposures I have been getting with my Godox/Flashpoint AD600TTL and decided to try a test to see what was going on. The Flashpoint AD600 is at the newest firmware and I upgraded both the T865 and X1T to the newest software this morning (1.7 and 13)

Camera is the Sony A7RII with Sony 85 1.4 lens.

The problems with underexposures seemed to be mostly with the AD600 but I decided to test both that unit and the TT685. All photos were taken at ISO 100, f4 on an A7rII with a GM 85 1.4.

The first line starts with a manual exposure (metered) to f4 with the AD600. In order are Manual f/4 - ETTL flat , ETTL +1, ETTL +1 1/3, ETTL 1 2/3, ETTL +2. All set via the trigger.

The second line starts with a manual exposure (metered) to f4 with the ATT685 In order are Manual f/4 - ETTL flat , ETTL +1, ETTL +1 1/3, ETTL 1 2/3, ETTL +2. All set via the trigger.

It looks as if my system is consistently underexposing by around 2 stops.

Any suggestions or ideas?

Jim

Another series as above metered to f/4 but using the TT685 as the trigger and the AD600 as the flash.

The sequence is the same -metered - flat ETTL - ETTL +1, 1 1/3, 1/2/3, 2.

Using the 685 as a trigger it looks like the AD600 is underexposing in ETTL by 1 1/3 stops.

Jim

All three together

First series using X1T as trigger with AD600.

Second series with X1T as trigger with TT685

Third series with TT685 as trigger and AD600.

In all cases it seems as if the system is underexposing considerably.

Are other Sony users seeing the same thing?

Jim

I have the Cheetah 600X and the Godox TT685S and neither underexpose in the examples that you mentioned.
Did you check to ensure that you do not have FEC in camera set to -2?

My A7rii, A7II is spot on in ETTL on the 600X and the TT685S....

Just to be sure I just checked No, the FEC in camera is set to "0".

The TT685 only underexposes by a little bit, the AD600 by a lot. Both work fine in manual mode.

Jim

Jim,
I'm going to do some testing following your model. I have noticed under exposure in TTL but it seemed circumstantial so I was discounting it.

Which camera metering mode do you have set?

I have found that metering mode has an impact on TTL metering.

And, since the metering mode changes the center weighting of the metered illumination, what reflector/modifier do you have on the light?

David,

I used Center Weighted. However all 3 choices seemed to have the same relative issues.

I used a small (24") SMDV Speedbox 60 softbox in all shots.

I would be very interested in your results.

This hasn't yet driven me to drink but I am considering it

Jim

I think you might well have a point. I just looked at the exif from my shots from the last studio shoot I did with the ad600. All my shots show at least +1 flash exposure compensation. I have another studio shoot later today and will pay closer attention.

Please let me know what you determine after the shoot.

Jim

What versions of firmware are in each of the devices?
Latest for AD600 is 2.2
Latest for TT685s is 1.7
Latest for X1Ts is 13

The reason for asking is that I updated by TT685s and X1Ts triggers with the latest firmware and when I did a test just now got really weird results.
I had the new firmware in the devices for my wedding last Saturday and didn't seem to have a problem with the TT685 on camera bounced, but there are under exposed frames with 4 AD600s at the reception. As well as a lot that are properly exposed.

While testing just now in the garage I had the TT685s on camera direct at Manny and it would underexpose and then would climb exposure to over exposed on subsequent frames without doing any changes to the settings. Both at 0FEC and +1FEC.
Same behavior with X1Ts on the A7RII. With TT685s as Slave in Gr A.


I wanted to do another test to confirm some things, so I took Manny into our sitting room to eliminate any glare that was coming back into the lens from the garage door.
What I discovered, is that the camera was set for a 5 frame 1EV bracket. I was using that for shooting outside at a car show Sunday.
Apparently affixing a speedlite or X1Ts to the hotshoe disables the continuous shutter firing but the exposure bracket still is controlling exposure.

Once I got the shutter set to single shot, the exposures are consistent. Now its a matter of looking at them in LR to see how far they deviate from property exposure.

I tried all three metering options, and all the flash setting options including wireless which resulted in a black frame.

I did a lot of testing with the trigger and TT685s before and did not experience this behavior.

I just looked on my windows computer and can't find the earlier version firmware. Nor do I know if its possible to retrograde the firmware.

I think Godox broke something with the latest update.

The TT685s update notes;
"Optimize the agreement with SONY camera hotshoe."
"Adjust the HSS function: adding SYNC button to control HSS function."
"To solve problem that the camera flash cannot achieve HSS flash when attaching to X1S"

I can't open the notes for the X1Ts so not sure what the updates were but probably similar.

I am using the most recent firmware in each device:
AD600 is 2.2
T685s is 1.7
X1Ts is 1

I did not run multiple tests at each setting but they appeared to be consistent from my experience. My previous experience with the TT685 ( with previous firmware) was that it seemed to be correct but that was in shooting in an uncontrolled environment with no testing. No way to go back and check now.

The X1T seemed to be underexposed with the AD600 in previous shoots (with the older firmware in the X1T) and is definitely underexposing with the AD600 (with the most recent firmware in the X1T) now.

Jim

Not sure about e-mount cameras, but in a-mount there is an option to disengage the flash exposure from the ambient exposure. By default the EC affects also the flash exposure, so if you have an exposure compensation of "-1", the flash is also compensated with "-1" even if the FEC is set to "0". To avoid this you must change the option "Exp.comp.set" from "Ambient&flash" to "Ambient only".
Maybe this is not the problem, or even the option is not available, but just in case.

Juan

Juan,
I just checked and the same option exists in "E" mount cameras. I had it set to Ambient & Flash(the default). I will change it to Ambient Only and see what happens. It should not have had an impact as the exposure compensation was set to zero but it's worth a try.

Thanks.

jim

Juan,

I appreciate the insight. I had not noticed this option before.

Unfortunately it did not solve the problem. Set either way the flash exposure is still considerably underexposed.

Jim

Jim,
I'll do some more testing tomorrow. One thought, the flash setting is called Fill-in Flash.
I wonder if Sony, like Canon, has an exposure bias for the flash presuming that its intended to complement the ambient.
I realize it makes no sense but that may be their logic. Especially since they also have a wireless option for multiple speedlite groups that Nissin uses but that Godox has chosen to ignore.