EOS 80D Overexposure on 80D problem

[BlairW]

I have a Canon 60D and an 80D, using a couple of my lenses or a Tamron 2x TC on the 80D (I know you guys are not a fan of converters) but I wanted to see if I could reproduce the same problem. That shooting in sunlight the camera is three f-stops too bright. If I manually correct it the exposure is just right. I noticed too even thou I set the ISO at an upper limit of 400 it is shooting at 6400 in green mode or program mode. I’ve cleaned the contacts with a contact cleaning kit. I don’t know if the camera has a metering problem or if I’ve changed one of the settings. BTW I'm not shooting into the sun or have the sun at my back, it's overhead. thanks, Blair

[Waddizzle]

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@BlairW wrote:
So, when I send the camera erroneous data (thru my mirror lens or combo of TC +lenses) it thinks it’s making the right exposure?

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Your mirror lens does not transmit data.  Only your AF lenses and extender transmit data.  Your initial question blurred the lines between two entirely different shooting scenarios.  In both cases, conditions are present bad data to the camera body.

The mirror lens neither transmits or receives data with the camera body, so the camera may yield unexpected results when the camera is in modes that try to control aperture.  If you are not using M or Av modes with the lens, then you are not using it properly.

Lenses transmit aperture data to the camera when it focuses.  The camera typically focuses at the maximum aperture setting of the lens, and then stops down when the shutter is activated, which causes the lens to transmit an aperture setting.  Until the most recently released Canon DSLRs, except for the flagship models, none of the cameras could focus with apertures as narrow as f/8.  

The firmware in the camera disabled the AF systems with apertures smaller than f/5.6.  Your 80D has no idea what the aperture setting is for your mirror lens.  Have you tried to use Live View with the mirror lens?

[LorraineS]

i have two copies of canon 80 d...while the detail is awesome iso is problematic.  on manual the auto iso is always overexposed on one body.  the other body has a noise problem.  i'm a bird photographer and usually set the shutter speed at least 1600 should a bird take off.  aperture i set from 5.6 6to 7.1.  i choose auto iso.  it is so frustrating becaue the shots are overexposed even though they look great.   i have used two copies of the 70d for three years with no problems at all.  i shoot with a canon 100-400 mm  ii lense.

also the sports mode does not go above 640 shutter speed?  the 70d went to 1600 at the gate.

i'm so disappointed.