6D Vignetting

All 6D owners who have tried using the camera on extremely low light, have you noticed any vignetting specifically on the top-left and top-right portions of the image?  I will upload pic later to show an example.  Fyi lenses used when I observed this outcome are 50mm f/1.4 USM and 24-105 f/4L.

--
JCC
"Photography is therapeutic."
http://www.pbase.com/joshcruzphotos