Grossly over exposed images during rapid shooting Canon Mk III

[Bundu]

Recently I had a problem with my new Canon 5D Mk III. My passion is photographing birds in flight and suddenly and ocasionally during rapid shooting the images are grossly over-exposed. I use manual exposure of 7.1 or 8.0, Auto ISO, High-speed continuos shooting, AI Servo AF mode and AF area selection.

The images below illustrate tha issue. All of a sudden the ISO shoots up from 800 in normally exposed images to 12800

in the over-exposed photos?

Has anyone experienced the same problem and if so how was it resolved/

[cicopo]

I stopped using Auto ISO because it's not very consistent in picking a "Best ISO" for most situations. It seems to favor allowing a high SS over everything else.

[Bundu]

Thank you for your advice. Would you say the ISO jump is an inherent fault of the Camera, and how is it resoled?

[cicopo]

I don't have that body but I'd say it's the fault of the software wrote to instruct the full line up of bodies with Auto ISO.

[TTMartin]

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@Bundu wrote:

Recently I had a problem with my new Canon 5D Mk III. My passion is photographing birds in flight and suddenly and ocasionally during rapid shooting the images are grossly over-exposed. I use manual exposure of 7.1 or 8.0, Auto ISO, High-speed continuos shooting, AI Servo AF mode and AF area selection.

The images below illustrate tha issue. All of a sudden the ISO shoots up from 800 in normally exposed images to 12800

in the over-exposed photos?

Has anyone experienced the same problem and if so how was it resolved. 

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I use Manual exposure mode with Auto ISO all the time on my 7D Mk II with no issues. 1/4000 is about twice as high a shutter speed than you need for birds in flight. I don't see that causing the issue so that was more of an observation.

The date stamp on the two photos are 5 minutes apart and the numbering indicates they are 10 frames apart. It might be more helpful to see the photo immediately preceding the overexposed one. 

[Bundu]

Above is a sequence of for images all taken at the same burst on TV prioity, the details for the first and second above are depicted below. The same story for the 3rd and 4th as far as the iso jumping from 640 to 12800 then back to 640 for the last image.

In the previous example of flying birds I have normally exposed images following imediately after the overexposed images taken at the same time

I look forward to your comments.

[kvbarkley]

You really need to try it in manual mode so that there is no autoexposure.

The only thing I can think of is that there is a loose flap of something that occasionally covers the exposure chip when the mirror is moving rapidly.

You might take the lens off, put the camera in cleaning mode and look inside to see if you see something.

[Waddizzle]

I had a similar issue with random over/under exposures.  I never really figured it out, because it seemed to resolve itself when I started using back button focus.  My best guess is that my thumb had nothing to do, so it may have hitting Exposure lock button.

[TTMartin]

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@kvbarkley wrote:

You really need to try it in manual mode so that there is no autoexposure.

The only thing I can think of is that there is a loose flap of something that occasionally covers the exposure chip when the mirror is moving rapidly.

You might take the lens off, put the camera in cleaning mode and look inside to see if you see something.

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I agree it could be that the mirror is sticking up, which would keep light from reaching the metering sensor.

[Bundu]

Thank you for your comments and suggestions.

Yes I do use manual for flying birds, normally an F stop of 7.1 or 8, and Auto ISO  - these are illustrated in the first images where the ISO set at 800 for the normally exposed and then suddenly jumped to 12800

In the next sequence I used TV -shutter priority @ 1000. the normally exposed image F7.1 and ISO 640, and the next photo adjusted the exposure to F6.3 and the ISO jumped to 12800.

So it happened in rapid shooting both in manual and shutter priority?