Compare Sigma 105mm f/2.8 Macro EX, Canon 100mm f/2 USM and Canon 135mm f/2L. No post processing or editing. No filter used. Canon D30 on tripod. f/8 aperture in all shots, overexposed by 1 to 1.5, shutter speed ranged from 1/20 to 1/15, ISO 100, Aperture-priority mode. Conclusion: Sigma lenses, if and when you do get a good one, are quality glasses for the money. It's on par with Canon optics, IMO. Sigma quality control process is yet to be desirable!!!