6D + 580EXII serious TTL metering problem?

[Arthur_Nunes]

I've through a lot of trouble using my new 6D with my 580EXII on TTL mode.

I used to use the speedlight with my T2i using center weight metering and it worked flawlessly all the time

Now with the 6D, it heavily underexposes at random intensities. I have to set it to +3ev compensation to get usable slightly underexposed images (not perfect but ok to lift on post). some times +3ev over exposes and I have to set +2 or +1.

I used that flash with T2i for 3 years so definitely I'm not commiting any dumb misconception while metering or analysing the situation. I always shot events using center weight metering on T2i and it worked great.

ps: I'm using magic lantern. I'm already using it for about 4 years and I know it may have bugs but now sure if it affects the metering

 

[Marsu42]

Now with the 6D, it heavily underexposes at random intensities. I have to set it to +3ev compensation to get usable slightly underexposed images (not perfect but ok to lift on post). some times +3ev over exposes and I have to set +2 or +1.

We're talking about *e*ttl here, right, not dumb old-school ttl? The 6d's metering is somewhat dodgy and this sometimes affects the flash, too, I'm afraid to say... +-1ev miss might be to be expected. Try flash exposure lock before focus & recompose with another metering than evaluative.

But could you please detail your problem? You're setting the *camera* to +3ev *ec*, or the flash to +3ev *fec*, and why would any of these lead to underexposure? If so, it sounds like your flash is broken and only operates with reduced capacity - they do this before they completely brake down (happened to my 600rt).

ps: I'm using magic lantern. I'm already using it for about 4 years and I know it may have bugs but now sure if it affects the metering

It doesn't. But if you want to be sure you'll have to debug it, i.e. start the camera w/o ML and try to reproduce the problem.

 

[Arthur_Nunes]

Manual mode shows that it still have lot of power left by ETTL so there's no capacity issue

I tested the flash with a T2i recently and its Ok.

setting +3ev on camera and on flash is making the same results. ETTL communication is Ok because I can change flash settings via camera (custom functions, etc..)


I'll try to debug ML and to use another metering system on field and I'll come back here later. Thanks Marsu42

 

[brianleighty]

I've through a lot of trouble using my new 6D with my 580EXII on TTL mode.

I used to use the speedlight with my T2i using center weight metering and it worked flawlessly all the time

Now with the 6D, it heavily underexposes at random intensities. I have to set it to +3ev compensation to get usable slightly underexposed images (not perfect but ok to lift on post). some times +3ev over exposes and I have to set +2 or +1.

I used that flash with T2i for 3 years so definitely I'm not commiting any dumb misconception while metering or analysing the situation. I always shot events using center weight metering on T2i and it worked great.

ps: I'm using magic lantern. I'm already using it for about 4 years and I know it may have bugs but now sure if it affects the metering

I think I've experienced what you're talking about to some degree. Can you give me some more details of what shooting settings you were using? When I've had this issue, it's almost always had something to do with the shutter speed. If I work in manual mode while still using ETTL I don't seem to have these issues. For whatever reason it sometimes decides to way underexpose.

 

[Rob]

I have the same problem with my 5D3 & 580 1&2, It just underexposes with the flash attached quite a lot, and other times its perfect, but I have got used to it and can now adjust a bit for it when I think its going to happen e.g back lit subjects always under expose, which I understand why this happens it didn't do this with my other 5Dc & 5D2, they seemed to read the situation better and illuminate the subject correctly with whatever flashgun I had on it. Im not actually sure if its the way the mark 3 meters with the flashgun or if my setup is malfunctioning? but its not that bad to make me go to the trouble of sending it away to get checked yet.

 

[Marsu42]

Im not actually sure if its the way the mark 3 meters with the flashgun or if my setup is malfunctioning? but its not that bad to make me go to the trouble of sending it away to get checked yet. :

I cannot really say because I've got a 6d, but I know with this canon cut some corners and the metering isn't really that reliable. Same might be with the 5d3 in far in between cases vs. the time-tested 5d2/5dc old-school metering... one of the reasons I see to buy a 1d camera as Canon puts much more effort into testing and calibrating these.

 

[Arthur_Nunes]

Exposure Configuration used on the described situations is:

Manual mode
Usually wide open (95% of the time)
bouncing light on ceiling and/or wall
happens with any ISO, whether LV or VF

I have a theory that 6D may have some sync problem with the ETTL preflash. It keeps firing the wrong output while the composition or camera position remains similar, but changing both will make a different ettl reading and consequently wrong output

 

[rado98]

Similar issue here with a 7d and a 430ex2, coming from a 600d.
Never had an issue with the 600d, with the 7d I get some 1 to 2 stops underexposing, depending on the situation, coloured/high ceilings/walls that would require close to full power seem to make the issue worse. Seems to work fine with the flash pointing forward, not that there is much use in that.
I tried reseting all settings on the flash and camera and uninstalling ML.
Sometimes powering off the camera and flash or changing a couple of settings seem to help bit not predictably.

 

[Marsu42]

I tried reseting all settings on the flash and camera and uninstalling ML.

You don't need to uninstall ML, just pressing SET (on most cameras, some have another key) on camera start disables it.

coloured/high ceilings/walls that would require close to full power seem to make the issue worse.

That points to a broken flash - just because it's still flashing doesn't mean it's 100% ok.

Flashing at or near max power can introduce small cracks in the tube, leading to unpredictable behavior. Letting the flash cool can "repair" it - that's probably the reason why it's hard to trace. I imagine a semi-broken flash might very well fire prematurely when the power build up is too high for the tube to carry.

Always use your gear properly, and in this case this means rather buying a "big" flash and not flashing at max power with a "little" flash esp. in quick succession.

 

[tdrive]

My 6D and 430EXII was also very unreliable. So much so that you either were forced to use FEL or manual flash. Strangely the flash worked reliably on my 60D, and both had magic lantern software on it. In the end i sold the 6D body and slowly but surely (regrettably because of the expense) starting to use Nikon again.

 

[Joey]

It used to puzzle me that I found it difficult to get decently exposed shots with my 580 or 430 flash units on my EOS 30D in a room with light coloured walls and ceilings and bouncing the flash. I often had to dial in 2 or 3 stops extra exposure to get it acceptable.

I still have the same flash units but on my EOS 7DmkII they both expose fine as far as my initial tests show. Problem with the EOS 30D flash exposure algorithm? It was particularly galling since years ago my old Canon T90 with its dedicated 300TL flash worked so beautifully well together, whether providing primary lighting indoors or fill lighting outdoors. Never had to adjust the automatic settings.

 

[jepabst]

I have experienced same with the Canon 6D. Massive under exposures on center weighted e-ttl on multiple flash manufactures; in fact, when using 6D in ttl mode, I just use average now - which seems to get the shot right.

I've gotten these massive under exposures on Yongnuo, Gotix, and Canon 480

 

[brianleighty]

I have experienced same with the Canon 6D. Massive under exposures on center weighted e-ttl on multiple flash manufactures; in fact, when using 6D in ttl mode, I just use average now - which seems to get the shot right.

I've gotten these massive under exposures on Yongnuo, Gotix, and Canon 480

I'll have to try that out. Thanks.

 

[Spiros Zaharakis]

I always use "average" instead of evaluative mode. Evaluative will always underexpose if there is enough ambient light.
I only had some issues with underexposure using bounce flash in high ceilings or far away walls. It seems like auto flash exposure wouldn't allow the flash to shoot at high power output.
However I have switched to manual flash when i shoot bounced flash as it is more reliable and predictable.
I only use TTL when I shoot with direct flash.
Also check that you haven't set FEC on both the camera body and the flash. I am not entirely sure which is correct but I think that FEC in camera overrides FEC on the flash or it is the other way round.

 

[alexturton]

This happened on my 7d. Turned out to be a dirty contact on the flash