It seems a new issue has popped up for the Canon 5dmk3. Multiple people are reporting that there is a light leak through the top LCD panel that directly affects metering. The easiest way to detect this issue is to put the body cap on the camera body as well as cover the viewfinder. Then place the camera in "P" mode at ISO800 and press the LCD backlight button.
As you can see in the video, the shutter speed changes depending on whether the backlight is activated. Similar results are achieved when a flashlight is shone onto the top LCD. Some users are even reporting that direct sunlight or walking into a room with bright overhead light is enough to sway the meter. If you are one of the lucky ones who managed to purchase a 5dmk3, it might be worth doing this little test to see if you need to seek a replacement version.
Test Procedure:
Remove lens and place the body cap on the camera body.
Place the viewfinder cover on the viewfinder.
(This should theoretically block any light from entering the camera.)
Set ISO to 800 and set the camera mode to "P".
(You should see a shutter speed of around 10 sec.)
Now either shine a flashlight near the top LCD panel area or simply turn on the backlight for the top LCD panel.
This will cause the shutter speed to fluctuate between 5-8 seconds, indicating light leakage.
Video example of sunlight affecting metering:
1st/featured video contributed by Sean Jaeho Yi
but even so, nobody's shown that it impacts the photo being taken... maybe just gives the wrong exposure.
perhaps for those who use a lens cap to make it a pinhole camera?
3.500 US$ for that?
Was this story sponsored by Nikon perhaps? ;)
While is seems to be an issue, it's not a major one in the field it seems. As if there's no small issues with lots of other cameras.
This story is a perfect example of what happens when you need to reach "n" stories a day. They don't have to be useful, they don't have to make sense, they just have to exist.
Does the exposure change if you are in direct sunlight, and then cover the lcd screen with a thick cloth?
My concern is that if the light is in fact leaking onto the sensor, it would alter the colour of the picture as well, since the LCD light will most likely have a different colour temperature than the ambient light.
Throwing off the meter is one thing, and arguably minor (although still an issue for a $3500 camera), introducing artificial lighting to my photos is definitely intolerable. People would not be paying $1000 for a camera without an IR filter for astro-photography, if they are not looking for perfection. And a large portion of the people who are paying 3.5k are looking for the same perfection.
So yes, the problem would most likely be unnoticeable by most shooters, but it doesn't change the fact that it could be a potentially significant defect. And it is up to reviews like this to help keeping consumers informed.