I own neither a Canon or a Nikon. What options are available for being able to change the aperture on the fly when using on Micro 4/3rds?

im struggling to understand how that works, having seperate aperture blades in the adaptor itself. Would you set the lens to 1.8 and then be able to adjust on the adaptor for stopping down? Without a Canon or Nikon body, how would I even be able to set the lens to 1.8?

fantastic! i'm sold!

The more I look at this the more it becomes a no brainer. I'm going to sell a couple lenses in this range and just pick up this bad boy. Throw a couple FF lens straps on it and call it a day. Great for eng type stuff.

I have the novaflex nikon adapter I use with my GH2 -- very nice, stopless aperture control so you can use it with G lenses like the Tokina 11-16. I'm also excited about the idea of getting this zoom and a speedbooster or lens turbo, but they don't make them for Nikon lenses yet.

Performance starting from wide end

http://www.ephotozine.com/article/sigma-18-35mm-f-1-8-dc-hsm-a-lens-review-22257

In German, and unfortunately no video samples. Just stills.

All the photos I have seen show the lens with electrical contacts (probably photos of EF mount). I emailed them about the Nikon version having the physical iris lever and got this confirmation:

Hello, The lens has a mechanically controlled lever actuated diaphragm and we are just starting to ship it in the Nikon mount this week. Yours Truly, Paul Pizzano Sigma Corporation of America

The Sigma 18-35mm F1.8 DC HSM is a fast and tack-sharp lens from F2.8 onwards, and one that exhibits low chromatic aberrations. Vignetting at wide-open apertures and barrel distortion at 28mm are the only real optical issues of note, something that other fast wide lenses also suffer from, and stopping down to F4 solves the light fall-off problem altogether.

Build quality is also excellent, with the brass lens mount and sober all-black design adding to the high-quality feel, and Sigma have even generously included a very good lens hood and padded case. The internal HSM focusing was very quick on the Canon EOS 700D that we tested the lens with, and manual focus over-ride at any time is a great feature.

http://www.photographyblog.com/reviews/sigma_18_35mm_f1_8_dc_hsm_review/

and here on a T4i:

Yep, also this data is added to dpreview lens review at

http://www.dpreview.com/previews/sigma-18-35-1-8/3

Sigma 18-35mm f1.8 is worth every penny bringing top of the line build quality, amazingly wide apertures, zoom abilities, and fast autofocus for only $799.

http://learningcameras.com/reviews/4-dslrs/166-sigma-18-35mm-f18-hsm-lens-review

That is a big lens, love to see it mounted on a GH2. Might need a lens support, particularly with u43 adapter.