Difference between Sigma 15 macro generation and second generation

the difference between the first generation and the second generation of Sigma 15 macro: the two generations of Sigma 15 macro heads have made great differences in lens size and filter aperture. The Jiao Wai spot of Sigma 15 macro is very round, with almost no bilinear, purple edge and onion rings, which is considered as a good Jiao Wai performance. The second generation is a macro lens with a focal length of 15 mm.