80D sudden exposure flicker in full manual video

[Canoonista_CZ]

Hi guys, I hope you can help me with the following issue, I've been facing with my 80D.

Almost everytime I shoot a video sequence longer than a couple seconds with 80D, there's a sudden and abrupt change in exposure. Everything is turns very overexposed for a couple frames, then it goes back to normal, thus ruins the shot. Does it wide open as well as stopped down to f8+. Seems to me like the camera is hunting for focus - yet all is in manual and AF switch on the lens is turned off. Does the same even when the AF is enabled.

I haven't experienced this kind of behaviour with my 6D, so this is quite new.

Lens used is Tamron 24-70/2.8 Di VC USD.

Thank you.

[Waddizzle]

No way near enough information to give you a wild guess.

What settings are you using when "all is in manual"?  What metering mode are you using?  What are your lighting conditions?  Is it backlit?  Indoors or outdoors?  What is your White Balance setting.

Get the idea.  Try to provide enough information so that someone can try to reproduce your issue.

[Canoonista_CZ]

Hi Waddizzie, ok, let me try to summarize my settings:
- picture profile is almost always CLOG from DELUTS or Marvels Cine
- manual ISO/manual aperture/manual shutter
- evaluative metering
- lighting conditions didn't matter, did it outdoors as well as indoors, backlight as well as front-light
- WB is either Sunny or AWB
- I'm using SanDisk SDXC 64GB EXTREME PRO 95MB/s class 10 UHS-I U3 V30
- recording in PAL 25/50fps
- doesn't really depend on the AF mode, as it had the same behaviour even when the AF on the lens was off

[Waddizzle]

Contact Canon.

[diverhank]

I'm grasping at straws here, but you may want to make sure Exposure Safety Shift is disabled...

[Canoonista_CZ]

It's always disabled 🙂
OK, seems like will need to bring it to Canon...

[Waddizzle]

---

@Canoonista_CZ wrote:

It's always disabled 🙂
OK, seems like will need to bring it to Canon...

---

Yes, contact Canon.  No doubt, they will ask you if this issue occurs with Canon lenses.  Does it?  

Next, they will point out that they cannot, and therefore do not, guarantee compatibility with third party lenses.  Canon does not make the gear, so they cannot guarantee peformance.

Finally, I want to point out that unless you use a fully manual lens, one with an actual aperture ring, then your aperture setting is always under the control of the camera.  I'm not sure how Exp-Sim, exposure simulation, works in video mode, but something tells me that it could be related to your issue.  

I also think that the flash of overexposure you are seeing is being caused by the lens aperture being stopped down to your "setting".  I would almost bet that it does not happen if you shoot wide open.  I would bet that it does not happen with Canon lenses, either.

[tmturver45]

I am having the same issue. Did you find the problem?

[Canoonista_CZ]

Nope 😕
It seems as a Tamron/Canon combination... Might be the reason why I get rid of the 80D.

[Waddizzle]

---

@Canoonista_CZ wrote:

Nope 😕
It seems as a Tamron/Canon combination... Might be the reason why I get rid of the 80D.

---

 I would have dumped the Tamron lens.