I test the Sigma 18-35mm F1.8 DC HSM Art Lens on the Sony a6000. Link to lens: http://geni.us/tQiP
The Sigma 18-35mm f1.8 Art lens is an interesting combination on the Sony a6000 because of Sony's missing fast aperture zoom lenses. In order to use this lens, you'll need to use several adapter options that are available for this sigma lens. The one I highly recommend is the Sigma MC-11 which gives the best performance and compatibility.
This video is more like a mini review of the Sigma 18-35mm f1.8. I don't cover the video aspects of the lens too much, but cover the image quality this sigma lens on the Sony a6000.