Calibration for what? I think you refer to DSLR lenses because mirrorless lenses don't need AF adjustment or calibration.I'd buy the Sigma 16mm f/1.4, but I've heard the lens might need calibration.
I've also heard of Sigma lenses so far out of adjustment that they can't be calibrated.
If I had a tech who I trusted to calibrate it, it would fine, but I don't...
Sorry to spread rumors. Google for "sigma calibration" if you want sources.
So it would be great if Canon made a 15mm !
Do Canon lenses ever require calibration straight out of the box ?