EOS 6D auto ISO not changing or being set correctly

[tmitch554]

I haven't used my camera for a few months now but just today after wanting to use it, I'm noticing that the auto ISO setting is not working as I would expect it to anymore. In every mode I have the auto ISO set and have changed all sorts of combinations that would make the shot underexposed but the ISO gets set to 100 in every instance. For example in a somewhat dimly lit room I've set the camera to aperature priority at f/4 with auto ISO. Focusing sets the shutter to 1/1000 and ISO to 100, which makes for a completely black shot. Similiarly, I used shutter priority at 1/200 and focusing sets the aperature to f/10 and ISO of 100. Shooting through LV works fine though, however, I know shooting using LV vs VF works differently so I take that with a grain of salt.

I've checked my settings for the auto ISO and it's all default settings, and I even just reset all the settings to make sure. This essentially makes most of my shots underexposted unless I put it in manual mode and adjust the shutter and aperature appropriately, even with it set to auto ISO since it will default to 100. One thing I have noticed is that sometimes when adjusting/setting the auto ISO, the camera will pick the correct one, but then very quickly change back to 100. I've also turned off ALO and HTP and that has done nothing. I am also using the newest firmware. It's almost as if the camera's light sensor is overly senstitive, thinking that what it sees is going to be overexposed, thus setting the ISO way too low.

[wq9nsc]

Can you manually select any ISO speed that you want?  If so, set it to 800 and adjust aperture and shutter speed so that you are getting a standard exposure (from review of the image) and see whether the metering indicates overexposure while composing/viewing the scene.

Are you sure you didn't accidentally set the auto ISO range to restrict it to only 100?  I have never used a 6D but I know that with my 1DX series bodies, setting regular menu option settings back to factory is done under the fourth set of menu items while custom functions are reset under the fifth set of menu options so putting everything back to factory default requires two choices in two different menu groups.

Rodger

[Waddizzle]

Try resetting the camera back to factory defaults.  

The only reason I an think of for the cameras to change from ISO Auto to ISO 100 is you are using one of the Custom Shooting Modes.  Using a flash, or exposure compensation might explain the behaviors.  Having Safety Shift can cause the settings to change unexpectedly, too.  Also, make sure the ISO Auto setting does not have an upper limit set to ISO 100.

[tmitch554]

Yes I did previously try to reset to factory settings, so the ISO speed settings were set to the default, which the ranges are set to "100-12800" for auto ISO. Safety shift was also disabled.

I set the camera to manual mode with an ISO of 800 with the lens cover on and a shutter speed of 1/1000 and aperature at f/4 and it was showing a metering of almost +3...

[Waddizzle]

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@tmitch554 wrote:

Yes I did previously try to reset to factory settings, so the ISO speed settings were set to the default, which the ranges are set to "100-12800" for auto ISO. Safety shift was also disabled.

I set the camera to manual mode with an ISO of 800 with the lens cover on and a shutter speed of 1/1000 and aperature at f/4 and it was showing a metering of almost +3...

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Are you sure ISO is actually set to Auto?  When the camera is in Manual shooting mode, the photographer controls all of the settings.  If you are metering +3 Ev, you may need to change aperture or shutter speed to bring it down.

BTW, the camera works best with the lens cover removed.

[rs-eos]

Try using the sunny-16 rule.  Set to manual:  f/16, 1/100 sec, ISO 100 should give a good exposure on a sunny day.  If you increase ISO to 800, then shutter would need to be 1/800 to maintain that exposure.

Then try P mode (which I think would work with Auto-ISO).  Set to f/16, 1/100 sec.  Was ISO 100 (or near 100) chosen?   Then set shutter to 1/800 sec.  Was ISO 800 (or near 800) chosen?

[wq9nsc]

With the lens cover on, the light meter should be pinned to/off the bottom of the scale.  It sounds like your camera has a hardware issue.

Rodger

[Waddizzle]

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@wq9nsc wrote:

With the lens cover on, the light meter should be pinned to/off the bottom of the scale.  It sounds like your camera has a hardware issue.

Rodger

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Yes, it could be a hardware fault, or a dirty metering sensor.  I'm just not convinced something is broken, yet.  Not if it works one memoent, then doesn't work the next moment.  And, then go through another cycle of working and not working one more time.  Digital electronics tends to be pass/fail when it goes bad, not intermittent.

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What type of lens are you using?  Have you tried a different lens?  

[tmitch554]

I've used two different lenses with the same results.
Canon 24–105mm f/4L

Canon 70–200mm f/4L

I did another few tests in a room with normal sunlight.

Two shots in Program AE:

First shot with auto ISO on, camera picked 1/160s f/9 ISO 100 and resulted in a black photo.

Second shot in LV with auto ISO on, camera picked 1/40s f/4 ISO 320 and resulted in a regularly exposed photo.

I did notice that if I manually set the ISO higher to 600 that the camera would simply change to f/13 and take another black photo.

Two shots in Manual:

First shot with auto ISO on, camera dialed to 1/200s f/4, camera picked ISO of 100 and resulted in a black photo.

Second shot with ISO manually set to 2000, dialed to 1/200s f/4 resulted in a regularly exposed photo.

[Waddizzle]

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@tmitch554 wrote:

I've used two different lenses with the same results.
Canon 24–105mm f/4L

Canon 70–200mm f/4L

I did another few tests in a room with normal sunlight.

Two shots in Program AE:

First shot with auto ISO on, camera picked 1/160s f/9 ISO 100 and resulted in a black photo.

Second shot in LV with auto ISO on, camera picked 1/40s f/4 ISO 320 and resulted in a regularly exposed photo.

I did notice that if I manually set the ISO higher to 600 that the camera would simply change to f/13 and take another black photo.

Two shots in Manual:

First shot with auto ISO on, camera dialed to 1/200s f/4, camera picked ISO of 100 and resulted in a black photo.

Second shot with ISO manually set to 2000, dialed to 1/200s f/4 resulted in a regularly exposed photo.

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I'm convinced. Sounds like an use with the metering sensor.  You should contact Canon Support, and schedule your camera for a repair.  

I still get the sense that there is something odd going on, though.  The Ev scale in the viewfinder should show you that the image is going to be underexposed before you take the photo.