Canon has admitted to a classic metering problem in their EOS 5D Mark III that 35mm film SLRs have solved for a very long time: stray light going through the viewfinder affecting the light metering sensor that resides in the viewfinder housing. In the case of the 5D Mark III, it’s the light from the LCD that is affecting the light meter sensor when it’s dark outside. The classic solution: a viewfinder door that shuts out all stray light from entering the viewfinder. It will be interesting to see what solution Canon comes up with in this case.
To Users of the Canon EOS 5D Mark III Digital SLR Camera
Thank you for using Canon products.
The phenomenon described below has been confirmed when using the Canon EOS 5D Mark III Digital SLR Camera.
Canon is now examining the countermeasures and once the countermeasures are decided, we will post the information on our Web site.
In extremely dark environments, if the LCD panel illuminates, the displayed exposure value may change as a result of the AE sensor’s detection of light from the LCD panel.
Canon EOS 5D Mark III Digital SLR Camera
Once the preparations are complete, we will be making an announcement on our Web site.
This information is for residents of the United States and Puerto Rico only. If you do not reside in the USA or Puerto Rico, please contact the Canon Customer Support Center in your region.
Please register the EOS 5D Mark III. By registering, we will be able to notify you via email when service updates are available. If you already registered, please ensure you are opted-in to receive the notification.
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Canon U.S.A., Inc
Contact Information for Inquiries
Canon Customer Support Center
For additional support options: www.usa.canon.com/support
Read the advisory here.