One of the lenses that i love to use is the Sigma 24mm 2.8 macro lens, the only problem is that it sounds like a tractor rolling over glass when it focuses. Should i go and buy the Canon 24 mm 2.8 and how do the two compare ? The only problem i believe with the Canon 24mm is that its not macro. Would I fall into the bracket of equipment fetishist if i brought the Canon as well ? Or is it justified quality wise ?