I love the Sigma 24-105 - it is beyond awesome in my opinion. I bought it specifically to use on my 5DSR because of the IS and the fact that it is very center sharp at all FL and easily out resolves the Canon 24-105 - especially at the longer portrait focal lengths - obviously the two downsides are lack of weather sealing and the weight. I have a wedding next weekend and I am going to go with 1 main camera, my new 1DX II with the Sigma - because the venue won't require a 70-200. That said, I will use the A7Rii with the Canon 24-70 F2.8 II during the ceremony because I like to shoot in silent mode and IBIS gives me a stabilized Canon. I have to update my sig because I just traded in the 135L to buy my new 1Dx II. I'm at a bit of a cross roads lens wise because with the 5DSR I really want IS lenses and the 135L is impossible on that camera at normal SS - on the A7R II it is awesome. I was looking at the new Tamron 1.8 VC, but something is just not right with the VC - it is creating blurs at 'normal' shutter speeds on the 5DSR.










