I'm trying to decide between the Canon EF 24mm f/1.4L II or Sigma 24mm f/1.4 DG HSM Art for some wide angle, low light work I'm going to do. Normally I'd just use my Nikon D800 and the Nikon 24 f/1.4, but I have access to a Canon 5DS R. I've done some looking around online and it's no surprise that some prefer the Canon and some prefer the Sigma. I'm asking for advice here because with my D800, I shot the Nikon 24 f/1.4 side by side with the Sigma 24 f/1.4. Aside from the fact that the Sigma needed a fine tuning adjustment of either + or - 10, I found the Nikon to be the sharper lens, especially wide open. I"m not sure if I had a bad copy of the Sigma, or if it just needed to be calibrated with the dock. On the flip side, I once tested the Sigma 35 1.4 side by side with the Nikon 35 1.4 and found the Sigma copy to be better. Anyways, back to Canon vs. Sigma. Does the Sigma show improvements over the older design of the Canon? Back in 2008, I used the first version of the Canon 24 1.4 and found it to be a great lens. I guess I could always rent both lenses, but would prefer to stick with one.