Well, the only specific comparison I did was as someone suggested, Christmas tree lights in the background (maybe 16-18 feet from the camera), and focused at about 3 or 4 feet from the camera. The lights showed more round from the Sigma; from the L, they were distinctly oval. I gave this round to the Sigma. But for detail in the far distance, the L won easily, which revealed to me that it has more resolving power.
