Canon camera with Godox flash exposure problems

RandomViews · Jul 5, 2025

Hi Phototrio!

Can I have some help figuring out what's going wrong with either with my camera system or my understanding of my camera system?

I have a Canon 7D mark II, 100mm EF F2.8 L macro lens, two EF-25 II extension tubes, Godox MF12 macro flash, and a Godox XProC flash controller.

Manual ISO/sometimes Auto ISO, eTTL II, evaluative metering, manual mode, 1/250 sec shutter, f10, no exposure compensation.

This system worked fine for about year, and then something changed.

The problem is that exposure with flash is all over the place. I can turn the system on, it'll give me a few properly exposed images, but then it will decide that everything needs to be overexposed. I turn down the ISO, over exposed. Use exposure compenstaion on the flash with -0.3 stop, it will underexpose. Somtimes, it will decide to do the opposite and underexpose the image. I've even had one overexposed and one underexposed image consecutavely! I turn everything off and back on, and it will be OK for a few images again.

If I just turn off the flash off, the camera seems able to expose the image properly, but it still struggles with the low low light situations during the macro photography that I do.

I looked all over the interwebs trying to find an explanation or solution. I've reset both camera and flash to factory settings multiple times.

I might be open to buying a new camera or flash, but not both, and I am concerned that the problem won't be with the new thing and remain with the one that I didn't replace.

Any thoughts on what's happening?

Thanks!!

koraks · Jul 5, 2025

Welcome aboard!
Sorry to hear about your flash issues. It's been ages since I seriously used flash on an EOS system, and back when I did, I used canon-brand flash units, esp. the 420EX and 580EX. Never had a problem with those; exposure using eTTL was always spot on.

The first thing I'd try is to do some tests with the built-in flash of the camera. Forget about the Godox stuff for a bit (or macro, for that matter) and just do some shots with a normal lens and the pop-up flash. That'll at least show you whether the camera's eTTL system works reliably. If it does, then proceed to troubleshoot a camera-flash interaction problem - or just a hardware problem with the flash unit as such.

Patrick Robert James · Jul 5, 2025

Since you are using an aftermarket flash I wouldn't count too much on the exposure being accurate on an automatic mode. If you can, use it in manual mode. Especially since you seem like you are super close to whatever you are photographing. (Two extension tubes?)

It is possible that your lens isn't stopping down. You might want to check that. Easy enough. Extension tubes are also a possibility as a cause of your problem. You should try cleaning all the contacts between the camera and the lens. Canon can have an issue with dirty contacts (I've been using Canon for three decades). It doesn't take much although if any contacts are dirty it will usually throw the EE error.

Also try cleaning the flash contacts on the camera and the flash.

Hope that helps.

koraks · Jul 6, 2025

Patrick Robert James said:
It is possible that your lens isn't stopping down.

Easy to test as that will also affect non-flash exposures.

Patrick Robert James said:
Extension tubes are also a possibility as a cause of your problem.

Not so sure about that since the point of eTTL is that it doesn't matter what's in front, inside or behind the lens; the light that reaches the sensor is what's being measured. I've used eTTL in combination with low-end extension tubes (with EF contacts) many, many times.

RandomViews · Jul 6, 2025

koraks said:
Welcome aboard!
Sorry to hear about your flash issues. It's been ages since I seriously used flash on an EOS system, and back when I did, I used canon-brand flash units, esp. the 420EX and 580EX. Never had a problem with those; exposure using eTTL was always spot on.

The first thing I'd try is to do some tests with the built-in flash of the camera. Forget about the Godox stuff for a bit (or macro, for that matter) and just do some shots with a normal lens and the pop-up flash. That'll at least show you whether the camera's eTTL system works reliably. If it does, then proceed to troubleshoot a camera-flash interaction problem - or just a hardware problem with the flash unit as such.

Thanks, koraks! I almost forgot about the camera's built in flash! I just did a quick test of the built in flash with about 25 images at ISO 100 and ISO 3200, and each set of images were comparable and without any over or under exposure. This was using a Canon EF-S 18-135mm lens. I will test the built in flash more and with the 100mm macro lens to be sure. But, initial testing seems to indicate the camera works as expected. Thanks!

RandomViews · Jul 6, 2025

Patrick Robert James said:
Since you are using an aftermarket flash I wouldn't count too much on the exposure being accurate on an automatic mode. If you can, use it in manual mode. Especially since you seem like you are super close to whatever you are photographing. (Two extension tubes?)

It is possible that your lens isn't stopping down. You might want to check that. Easy enough. Extension tubes are also a possibility as a cause of your problem. You should try cleaning all the contacts between the camera and the lens. Canon can have an issue with dirty contacts (I've been using Canon for three decades). It doesn't take much although if any contacts are dirty it will usually throw the EE error.

Also try cleaning the flash contacts on the camera and the flash.

Hope that helps.

Hi Patrick Robert James! The Godox flash worked as expected for some time, so something changed somewhere in the system to cause the exposure issues. The flash on manual flash seems to work as expected, although even 1/128 seems to be too bright (a possible indicator for the flash having an issue). Once I tried eTTL, I was hooked. I photograph insects in the wild, so anything that increases the probablity of getting the exposure right in one image is welcomed. Taking an image and checking to see if the flash level was correct can be tricky because some insects leave the scene rapidly after one flash.

Checking out all the other components is a good idea. I looked at the lens contacts and they appeared clean, but I can run some rubbing alcohol over them just to make sure. I think the lens is stopping down correctly because a low f-stop is obvious in macro photography. The images look like they have the expected depth of field.

I'll also test the 100mm macro lens and each extension tube seperately with the pop-up flash (as best as I can) so see if the lens or tubes are introducting an error into the system. Definately a good idea to try to isolate each piece and test them.

Thanks!!!

RandomViews · Jul 6, 2025

koraks said:
Easy to test as that will also affect non-flash exposures.

Not so sure about that since the point of eTTL is that it doesn't matter what's in front, inside or behind the lens; the light that reaches the sensor is what's being measured. I've used eTTL in combination with low-end extension tubes (with EF contacts) many, many times.

Great looking image, koraks!

When my system works together, I think the results are good.

koraks · Jul 6, 2025

RandomViews said:
The flash on manual flash seems to work as expected, although even 1/128 seems to be too bright (a possible indicator for the flash having an issue).

This is something that's certainly worthy of further investigation; I'd shoot a series of 5-10 images on each power level setting and then see if there's any variance.

RandomViews said:
Great looking image, koraks!

When my system works together, I think the results are good.

Absolutely, that looks nice! And thanks; the fungi shoot was from many many moons ago; certainly >15 years. I used to do that a lot for a while. I used a Canon 20d at the time and as said a pair of Canon flash units. I mostly used those in an eTTL setup with a 580EX on the camera and a wireless-controlled 420EX auxiliary unit on a little stand.

wiltw · Jul 7, 2025

RandomViews said:
Thanks, koraks! I almost forgot about the camera's built in flash! I just did a quick test of the built in flash with about 25 images at ISO 100 and ISO 3200, and each set of images were comparable and without any over or under exposure. This was using a Canon EF-S 18-135mm lens. I will test the built in flash more and with the 100mm macro lens to be sure. But, initial testing seems to indicate the camera works as expected. Thanks!

So you know the nTTL flash automation is fundamentally working properly, and consistently. So that overexposure with the Godox is pointing to the probable issue is that the communication between camera and flash is being inconsistently connected.
When the nTTL is connected well, the camera tells the flash 'flash to pre-exposure', then the camera reads the amount of light reflected back from scene, then the camera commands 'flash to partial output X'.
But when the nTTL connection is flakey, the flash only sees 'Fire' and it outputs full power, and then you get an overexposure.

You can try to clean the flash contacts on the hotshoe and on the hotfoot, using a pencil eraser. Or you can try replacing a flash cord, if it is not the permanently wired connecting cord. Canon nTTL has been demonstrated over the decades to sometimes have this nTTL communication issue show up, regardless of brand of external nTTL flash.

RandomViews · Jul 9, 2025

wiltw said:
So you know the nTTL flash automation is fundamentally working properly, and consistently. So that overexposure with the Godox is pointing to the probable issue is that the communication between camera and flash is being inconsistently connected.
When the nTTL is connected well, the camera tells the flash 'flash to pre-exposure', then the camera reads the amount of light reflected back from scene, then the camera commands 'flash to partial output X'.
But when the nTTL connection is flakey, the flash only sees 'Fire' and it outputs full power, and then you get an overexposure.

You can try to clean the flash contacts on the hotshoe and on the hotfoot, using a pencil eraser. Or you can try replacing a flash cord, if it is not the permanently wired connecting cord. Canon nTTL has been demonstrated over the decades to sometimes have this nTTL communication issue show up, regardless of brand of external nTTL flash.

Thanks, wiltw!

I started some testing and began with a simple cleaning of the lens and tube contacts with a q-tip and rubbing alcohol. After this quick scrub, I went out photographing. The flash worked as expected. It felt good to see image after image come though properly exposed.

But, now, the focus is a little glitchy. It's subtle, but it takes longer to grab focus than before, especially at the near limit. My camera has always disliked focusing so close, but now it's slower than it was before. So the issue "moved" to something else, which to me indicates a possible contact issue. Your explaination of TTL connections agrees with what I found "experimentally" and was very helpful. I knew about the preflash, but I wasn't aware that without/a glitchy "partial output signal" causes full power output.

Why would the focus be glitchy now? The contacts look clean, but clearly something was causing a intermittent contacts. Maybe I move the dirt from one contact to another? I'll try the pencil eraser trick and see if that clears up the issue.

Thanks!!!

wiltw · Jul 10, 2025

RandomViews said:
I started some testing and began with a simple cleaning of the lens and tube contacts with a q-tip and rubbing alcohol. After this quick scrub, I went out photographing. The flash worked as expected. It felt good to see image after image come though properly exposed.

My instructions were to clean the FLASH contacts in the HOTSHOE and HOTFOOT. You say that cleaned the electrical contacts on the lens, which have nothing to do with nTTL automation. Cleaning lens contacts should not have affected focus, but perhaps you accidentally left something behind -- a bit of cotton -- that has degraded the contact which communicats the focus motor signal from body to lens! Brush all the contacts to see if it removes some debris. Or maybe there is some contamination in the alocohol which left residue on the contacts after the alcohol evaporated away...clean again with a fresh bottle of alcohol, even unflavored vodka!

koraks · Jul 10, 2025

wiltw said:
Cleaning lens contacts should not have affected focus, but perhaps you accidentally left something behind -- a bit of cotton -- that has degraded the contact which communicats the focus motor signal from body to lens!

This is a bit of a tangent, but this is not how the EF mount works. The body-lens communication is basically SPI data transfer, which means that it's commands and data going over a bus, with all functions being communicated over the same set of contacts (essentially just 3: DI, DO and CLK). Hence, disruption of this communication would affect everything involving the lens - so if focus is affected, the aperture will likely also not work. And since the communication is bidirectional and involves confirmations, the camera will simply throw an error if there's a lens-camera communication problem. There's basically zero tolerance for any of the contacts being intermittent as in all situations this will immediately trigger an error on the camera on startup.

Also, the focus and aperture motor controls are indirectly controlled in the EF system, by which I mean that the camera sends a command to the lens to run e.g. the aperture motor for x microseconds, and then the processor within the lens actually controls the motor. Focus seems to involve a set of three commands, two of which order the lens to shift focus to max (infinity) resp. min (closest distance), with the third command setting a particular focus point using a 16-bit numerical value as a parameter. The lens then autonomously controls the focus motor to perform the work requested.

RandomViews · Jul 10, 2025

Thanks, wiltw. I took off the flash controller, lens, and tubes to do the cleaning, so maybe that helped get the flash working previously?

I disassembled the camera system and cleaned all the contacts the same way I did before. Now, the flash is exposing all over the place, but it's not a drastic over- or under exposure like before. The exposure is just beyond what could be considered OK, but the image is still not exposed correctly, if that makes any sense. The focus might be acting a little bit better, but not enough for me to tell that it's back.

Koraks, thanks for explaining how Canon lens communications work. Very interesting.

The camera is not providing any error messages on the displays. Are there log files somewhere that are readable? Does this mean that issues with no error messages is either my insanity or these contact issues will plague me indefinitely with this camera system?

Thanks!

koraks · Jul 10, 2025

There's no clear indication of your problem being caused by contact issues. My feeling is that it's most likely to be internal to the flash unit itself. Contact problems within the flash unit may play a role, but could manifest themselves in many places. I'd be tempted to verify the camera works correctly with a different external eTTL-capable flash unit; I expect it will, but might be reassuring to verify this. You can then decide whether perhaps to replace your present flash unit with a new one.

RandomViews · Jul 11, 2025

koraks said:
There's no clear indication of your problem being caused by contact issues. My feeling is that it's most likely to be internal to the flash unit itself. Contact problems within the flash unit may play a role, but could manifest themselves in many places. I'd be tempted to verify the camera works correctly with a different external eTTL-capable flash unit; I expect it will, but might be reassuring to verify this. You can then decide whether perhaps to replace your present flash unit with a new one.

Thanks, koraks. I'll see what I can do about trying another flash unit. In the meantime, I’ll keep on with what I have and roll with the glitches. I'm at a junction where I need to decide if I want to put more into this system, upgrade to a newer Canon system, or try another brand. There’s a lot to choose from and I’m not in a rush to try to figure out what new system does what (and if that’s what I want), spend a bunch of money, and then realize that it really doesn’t do what everyone says and all has all this fancy stuff I probably won’t use.

I've learned several new things in this thread, and I appreciate that. Thanks!

koraks · Jul 11, 2025

You're welcome; I trust the situation will resolve itself one way or another. Hopefully you have some more clarity on how to move forward!

wiltw · Jul 11, 2025

Let me write about what I have directly experienced over 20 years with Canon nTTL flash automation, using different flash units and different camera bodies, to give a bit of insight...

I have experienced very 'ephemeral' (read 'flakey') flash exposures using Canon nTTL

with a nTTL flash on hotshoe, things would do from 'working properly' to 'overexposure', simply by putting a flash extension cable between the camera and flash...and this happened with four different flash extension cords -- two different generation Canon flash extension cords and two other different aftermarket brands, all of them new out-of-box cords!
with nTTL flash on hotshoe and camera mounted on tripod and shutter pressed very gently to avoid jiggling anything, in a series of a dozen exposures SOME (at random) would be overexposed while others would be exposed properly

...in view of tests with a variety of cameras (20D, 30D, 40D, 7DII) and flash units (Metz 54MZ, 58AF) and connections (direct hotshoe, 4 different brand/model extension cords), and in view of complaints from other users, I can only conclude there is something inherently weak in Canon nTTL design which makes it subject to connection/command transmission variability which randomly causes the system to fail to transmit the partial-flash-output command to the flash unit. As a result, when flash exposures go flakey, I immediately abandon nTTL and resort to using the photosensor Auto mode on the flash unit to eliminate use of the nTTL flash system entirely.

RandomViews · Jul 11, 2025

koraks said:
You're welcome; I trust the situation will resolve itself one way or another. Hopefully you have some more clarity on how to move forward!

This was very helpful. Knowing that the flash unit and its connection can be tempermental is very helpful and helps me ask good questions when it comes time to make a decision.

wiltw said:
Let me write about what I have directly experienced over 20 years with Canon nTTL flash automation, using different flash units and different camera bodies, to give a bit of insight...

I have experienced very 'ephemeral' (read 'flakey') flash exposures using Canon nTTL

with a nTTL flash on hotshoe, things would do from 'working properly' to 'overexposure', simply by putting a flash extension cable between the camera and flash...and this happened with four different flash extension cords -- two different generation Canon flash extension cords and two other different aftermarket brands, all of them new out-of-box cords!

with nTTL flash on hotshoe and camera mounted on tripod and shutter pressed very gently to avoid jiggling anything, in a series of a dozen exposures SOME (at random) would be overexposed while others would be exposed properly

...in view of tests with a variety of cameras (20D, 30D, 40D, 7DII) and flash units (Metz 54MZ, 58AF) and connections (direct hotshoe, 4 different brand/model extension cords), and in view of complaints from other users, I can only conclude there is something inherently weak in Canon nTTL design which makes it subject to connection/command transmission variability which randomly causes the system to fail to transmit the partial-flash-output command to the flash unit. As a result, when flash exposures go flakey, I immediately abandon nTTL and resort to using the photosensor Auto mode on the flash unit to eliminate use of the nTTL flash system entirely

Thanks, wiltw, for your experiences. They are very much in the same direction as what I’m seeing and have helped me think more clearly about this.

Do you know if the newer Canon cameras, like the R7 through to the R5markII, have these same idiosyncrasies?

Do you know of a camera brand that is solid when it comes to flash exposure consistency? I understand no system is perfect, but in terms of averages, who is the most consistent?

koraks · Jul 11, 2025

The 'random overexposure' issue can originate from poor contacts on the hot shoe. The flash will probably just fire at maximum power. The degree of overexposure will in that case depend on the regular factors like subject distance, aperture and ISO.

I don't expect newer cameras will be more immune to this. Nothing has changed structurally about the hot shoe. What might help is to move the flash unit away from the hot shoe (e.g. by means of an extension cable) since a unit balancing on top of the camera can create leverage on the hot shoe, which can produce poor contact problems. However, since you're shooting macro, I assume you're already working with an off-camera flash setup.

Any wireless communication mode would be immune to these physical connection problems, but may bring problems of their own.

In my experience, Canon's eTTL system is really quite reliable.

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