c2thew wrote in post #13373564
When I read "on par" that usually means that the image quality would produce identical images however in order to discern quality, sharpness is the major factor when deciding which lens is better. Color and saturation come in second. The 2.8 non IS has less contrast then the IS model in real life shooting situations. Being able to shoot at 1/30 (IS) vs 1/80 or 1/125 with the non IS is a huge real life factor. Besides the OP was comparing the IS vs IS mk2 as mentioned in the title of the thread.
I agree, most people (on forums anyway) seem to focus primarily on sharpness when talking about IQ. But IMO there is also bokeh, CA/fringing, distortion, vignetting and like you said colors and contrast to consider. There are all very important too. IMO Sometimes more important than sharpness. But I guess it depends on what you shoot and how you do that. To elaborate on that... the mkI's lower contrast (and to some degree pixel-peeping sharpness) may be favorable for portrait shooting. For other tasks it may be less desirable. I am aware that OP is considering an IS version. And sure IS helps with static subjects/objects. But it isn't of any help when tracking moving objects/subjects. OP mentions he likes to shoot people, landscapes and wildlife. Do the people and wildlife move? In what lighting consitions does he shoot them? Does he have a tripod when shooting landscapes? Does he have a steady hand? The point I am trying to make is, it is difficult to know wether he "needs" IS or not based on the given information... hence my suggestion to check out the non IS version. Of course he can do whatever he wants with this advice