This lens is constructed very well. There isn’t the amazing heavy-duty construction of the Canon 35mm f/1.4. Instead, I’d characterize the construction of the Sigma as very efficient and carefully laid out.
Each of the lenses have different disadvantages and advantages to them, but they chose the Canon lens over the Sigma. It all comes down to personal preference when choosing one over the other.
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Buy the Sigma 35mm f/1.4 from B&H Photo.