There's no doubt that these two lenses represent the best available to Canon shooters at the 135mm focal length. I spent some time comparing the Sigma 135mm f/1.8 ART head to head with the Zeiss Milvus APO Sonnar 135mm f/2...and here's what I found:
<iframe width="560" height="315" src="https://www.youtube.com/embed/_RnKTrJEcUQ" frameborder="0" allowfullscreen></iframe>
I never seem to be able to get the embedded videos to work, so if it doesn't here, you can use this link: http://bit.ly/MilvusvArt
<iframe width="560" height="315" src="https://www.youtube.com/embed/_RnKTrJEcUQ" frameborder="0" allowfullscreen></iframe>
I never seem to be able to get the embedded videos to work, so if it doesn't here, you can use this link: http://bit.ly/MilvusvArt