Earlier this month, reports started emerging that Canon’s new 5D Mark III DSLR has a “light leak” issue. Photographers found that turning on the LCD backlight in a dark room directly affects the camera’s metering system (as seen in the video above). Canon published a product advisory today acknowledging the issue, saying,
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.
The phenomenon [...] 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.
Problem is, the issue isn’t limited to the LCD’s backlight in a dark room. Apparently any light (e.g. sunlight) shining onto the LCD screen can affect exposure.
Here’s a video that shows how sunlight shining down onto the LCD affects the camera’s metering:
Canon has quite a mess on its hands if it’s unable to address this issue in a simple manner — it doesn’t seem to be a problem that a firmware update will be able to fix.
Update: Mitch points out that in the second video the user has the lens cap on, so the camera “thinks” it’s in a dark environment.