OK, I'm new to the 5D3 and noticed something strange when taking pictures of our Christmas Tree with the lights on. I was shooting inside tonight with no flash using the 5D3 with the EF 24-105mm f/4 L IS USM Lens.
I took 5 rapid fire shots of our tree - in the first three pictures there were missing lights on the tree - they were there, just not on. The last two pictures showed the same missing lights had magically turned on. These are red, blue, green and yellow LED lights - very bright to the eye.
I was shooting in manual mode with auto IOS that was around 12800
Update - sorry about this premature post - I found the LED explanation on the web...