Earlier we reported on what was being called a “light leak” and Canon now confirms that in extreme dark light situations, pressing the LCD backlight may impact metering. Please read the product advisory below.
We'll of course let you know when Canon issues a resolution statement.
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.
Customer Support Operations
Canon U.S.A., Inc
So, while we did agree earlier that there was a possible impact from the LCD light, it again doesn't appear to significantly impact most situations.[source: canonrumors.com]
(cover photo credit: snap from the earlier article)