The new 5D Mark III offers in-camera (peripheral illumination correction and chromatic aberration correction). Should I disable this and continue to use my LR lens correction functions?
This is a JPEG only effect when used in camera. The Raw file is not affected and the corrections can also be done by external programs (e.g. with Canon's Digital Photo Professional software). Lightroom offers its own version of those corrections.
If I leave it enable on camera, LR is not aware of and I can still perform function - Is this mean I am double down 
I didn't try it, but probably the Raw preview 'thumbnail' that's embedded in the Raw file will be affected. You might as well switch it off if it saves any in-camera processing time, when you process your files in Lightroom anyway.
Cheers,
Bart
