YankeeMom wrote in post #13549116
Chariot, is the picture quality/sharpness in the Sigma equal to the 85 1.8? I've only had Canon lenses, but would be willing to consider the Sigma, but if the 28 is as sharp as my 85, not sure.
I would say in good light (iso 1600 or less type of situations),
the Sigma is sharper in the center at all apertures. The 85 is sharper in the corners in all situations. The IQ falloff of the Sigma starts becoming noticeable just outside of the rule of thirds area. From what I have heard, the Canon 28 suffers lower IQ in the corners as bad or worse.
In low light, and by low light I mean ISO 3200 and f2 type of lighting, the image quality of the sigma starts to fall behind the 85/1.8 but I think that is a function of AF accuracy. Remember that no prime can turn bad light into good light, fast primes just have the ability to let in more bad light so having directional or off camera flash at least as a back up will do your pictures wonders.
What others have said about the Sigma having a yellow cast is true. I find this to be a non Issue because I shoot RAW. A five second adjustment of the white balance and a little extra vibrance boost in PSE elements and the color is corrected to that of my Canon Glass. If you are a jpeg only shooter, you may want to stick with Canon.