Canon EF 24-105mm f/4 USM L IS Analysis - on the EOS 5D Mark Ⅱ.

Source: PhotoZone
PhotoZone: The lens produces a massive barrel distortion of 4.3% at 24mm - this is highly disturbing for architecture photography or scenes with straight lines unless you correct the effect during post-processing. The situation eases soon thereafter and the lens reaches its lowest degree of distortions at 40mm (~0.7%). The problem increases again towards the long end of the range but the local pincushion distortions remain acceptable at around 1.5%.(...More)