From Canon 5D2 to 4 or R or 5 or Sony ?

[Dan Wells]

I hadn't realized one of the Sigma superfast zooms was FF (although a 24-35 has very little zoom range - it's not quite a 1.5x zoom) - I knew they had a few f1.8 and f2 zooms for APS-C (and Olympus has long been almost-publicly considering the idea for Micro 4/3). A 2.5x zoom like Canon built is significantly harder than an almost 1.5x zoom...

Dan