Sigma has somehow managed to do what no one else has done before. Create a zoom lens with a constant f/1.8 aperture. While this lens is an APS-C lens for cameras with a cropped sensor camera, the lens should also function on the Nikon D600 & D800 using their cropped modes. As a Sigma Art series lens, it will have a metal barrel, excellent build quality, and stunning looks. I have a feeling it will be an interesting day for Canon & Nikon as they sit with their mouths open staring at this announcement. 

No pricing or release information as of yet but I will keep you updated. More information at Sigma Global.

Sigma Global

Image quality until now found only in a fixed focal length lens. The definitive large-aperture APS-C format standard zoom lens.
A large-aperture fixed focal length lens is great for achieving expressive bokeh effects and enjoying ultra-high optical performance. On the other hand, photographers often need to change the angle of view to properly capture the scene that presents itself. To solve this decades-long dilemma, Sigma proudly introduces the SIGMA 18-35mm F1.8 DC HSM next-generation large-aperture APS-C format standard zoom lens for digital SLR cameras. Taking on the challenge of creating the world’s first* wide-aperture lens to offer an aperture of F1.8 throughout the zoom range, Sigma has succeeded in creating a zoom lens that offers the same high optical performance of a fixed focal length lens. These outstanding performance characteristics are especially apparent in an APS-C format camera, since it has a slightly greater depth of focus than a full-frame camera. This is a revolutionary lens that overturns preconceptions while expanding the range of photographic expression.
The full realization of the Art product concept for you to hold in your own hands and appreciate with your own eyes.

Designed with a focus on sophisticated optical performance and tremendous expressive power, our new Art line of lenses delivers top-level image quality. With unsurpassed expressive performance, these lenses reach the high standards demanded by photographers with an artistic, creative inclination. Along with landscapes, portraits, still-life, close-up and casual snaps, they’re perfect for the kind of photography that unleashes the inner artist. Ideal for studio photography, they offer just as much expressive scope when capturing architecture, starry skies, underwater shots and many other scenes. The full realization of the Art concept, the Sigma 35mm F1.4 DG HSM is the perfect flagship. Hold it in your own hands and appreciate it with your own eyes.

Lens construction

Vignetting

The x-axis represents image height (distance from center of image in mm), and the y-axis represents the relative illumination at the edge of the image

(with illumination at the center of the image defined as 100%). When relative illumination is low, the corners of the image appear dark, resulting in vignetting.

Distortion