I went into a shop to try one, the 35mm copy. (I have had the canon 35 mm in the past and I never should have sold it.) My experience was not good - i immediately saw chromatic aberration on the images I took in the shop and didn't bother to take my test further, maybe be it was a bad copy but the shop keeper didn't try to persuade me so kept my money in pocket. There is also a digital rev YouTube video about these lenses, think it's the 50mm in comparison with the canon one, and it does ok but the canon wins