This scene shot at 24mm with a FaderND gen 1 (works fine with the 24-105 lens) looks sharper than normal for a detailed wide angle shot: https://vimeo.com/40107424
It's not sharp, but it appears sharper than normal and requires less post sharpening (about 1/2 the amount). This example shows moire (church), which I haven't seen before with the 5D3 (well, have seen it before but very minor). More details in the vimeo description and original MOV available for download. Banding in sky likely due to using CineStyle and over-exposing the shot (could fix in post if this shot was needed using noise/grain or selective blurring with AE or Resolve).
If anyone has a FaderND (any version), Heliopan, etc., or clear linear/circular polarizers, would helpful to know if polarizers can help improve sharpness (some OLPFs use a polarizer- might be some kind of interaction with polarized light which reduces diffusion and blur).