You may have a fault with the diaphragm in the lens (the mechanical bit that gives you the different apertures).
To test this put the camera in M or AV mode, set the lens to the smallest aperture, look into the end of the lens and press the DOF preview button on the camera. Do this repeatedly and you should see the aperture close to the same size opening each time, repeat the procedure for other apertures. Try the same thing with and without the teleconverter.
When using my x2 teleconvertor and 300mm f2.8 mkii I occasionally get over exposure issues. I shoot in manual with auto iso 50% of the time it exposes perfectly. I then get loads of images totally over exposed. Tried all different metering types. Sometimes the over exposure is almost 2 stops. Sometimes by removing the lens and refitting helps. Any solutions please because this is now causing me many hours of grief and 100's of lost pictures.
I used to have this problem with my T5 and 6D. Note the past tense. I never did figure out what caused [it], but it went away.
The fact that it was happening with two bodies made [me] rule out the bodies, and examine what I could be doing. I noticed that it would only happen when I got into a “flow” of taking photos, so my attention was [elsewhere], on the subject and getting the shot, not on the details of using the camera.
As an experiment, I began using BBF, back button focus on the 6D. Coincidentally, I had also begun using a battery grip. It took about a month before I noticed that the occasional bad exposure seemed to have gone on a sabbatical. This was my only clue. And, the problem seems to have cured itself.
My best guess as to what I was doing wrong was that my thumb was wandering around, and locking focus. I had a habit of keeping the camera “awake”, so that I could take a quick shot. But, taking quick shots did not seem to have any impact on when a bad exposure would show up.
Once i started using BBF, my thumb had something to do, and was no longer locking exposure without me noticing. But, like I said, all of this is guess work and assumptions. All I know for certain is that I changed the way I handled the camera, and the problem went away.
When it happens it seems to last for over 50 shots in succession. I'll change from auto iso to manual I'll also under expose by up to 2 stops and still it will appear very washed out with it clipping the right on the histogram. Seems to happen more when the sun is in my face. I definitely think it's lens orientated as ive never had these issues with other lenses on the body.
I have the 1DXII and a series of L lenses. I have never had it happen for a long sequence of shots like you describe, but I always have it happen on some shots during a night of shooting sports. I can never figure out why, and generally it's only a few in a long sequence, so I just chalk it up to the fact that I'm panning/zooming while taking high rate bursts so the lighting is changing quite a lot from a sensor perspective, though perhaps not human perspective. I use BBF and tend to take my finger off the shutter button (set to Metering Start) from time to time during a burst. It's never so extreme that I cannot easily adjust the RAW file in post processing, so I don't worry about it too much. But again, I haven't had something like you describe with 50 shots in a row consistently improperly exposed.
I've received some feedback from the shop I got it from. They say check and clean the connectors between lens and camera. Will give this a try. I found with the amount of over exposure it has also lead to the images being very soft. To the point of unrecoverable.
Nonsense. Do not waste your time cleaning the contacts, not unless you can SEE something there.
Do you wear eyeglasses? Did you know that light entering the viewfinder through the eyepiece can affect the measured exposure? I wear eyeglasses and have long suspected this as a reason for a bad exposure.
I suggest looking less at the camera, and look more at what you are doing.
09/26/2023: New firmware updates are available.
08/18/2023: Canon EOS R5 C training series is released.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
03/30/2023: New firmware updates are available.