The worlds first lens offering an aperture of f1.8 thoughout the zoom range exclusviely for APS-C sensors.

• 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 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.
• To develop a large aperture zoom lens with a maximum aperture of F1.8, it was necessary to solve a variety of technical challenges. As the f-number decreases, so does the depth of focus, making it extremely difficult to minimize spherical aberration, axial chromatic aberration, astigmatism and field curvature. To minimize astigmatism across the zoom range, Sigma leveraged its extensive experience in reducing optical aberrations and designing advanced structural elements. Advanced production technologies have made possible a large-diameter molded glass aspheric lens, which teams up with SLD (Special Low Dispersion) glass elements to optimize power distribution and minimize axial chromatic and spherical aberration and field curvature. Thanks to its hard-earned knowledge of lens design and advanced lens manufacturing techniques, Sigma has succeeded in creating a lens that offers F1.8 throughout the zoom range, as well as exceptional image quality at wide open aperture.
• When photographing with point light sources such as electric lights or reflections on a body of water in the background, the rounded 9-blade diaphragm helps produce an attractive bokeh effect—even at large-aperture settings.
• Zoom lenses are extremely convenient, providing a wide range of angles of view with just a twist of the zoom ring. The downside, however, is that F2.8 has been the limit of zoom lens brightness, forcing photographers to select fixed focal length lenses for brighter f-numbers. Although fixed focal lenses have been superior to zoom lenses in terms of f-number brightness and overall performance, they offer only a fixed angle of view, requiring photographers to carry several with them and change lenses as necessary. The 18-35mm F1.8 DC HSM next-generation large-aperture standard zoom lens is the world’s first* to deliver F1.8 brightness throughout the zoom range. Its bright viewfinder makes it easy to confirm focus and compose perfect shots. As compared to a F2.8 lens in the same photographic conditions, it allows the photographer to use a shutter speed that is one stop faster, reducing the influence of camera shake. In addition, the shallower depth of field makes possible a beautiful bokeh effect in the background, expanding photographic creativity. From wide open to standard apertures, this lens is highly flexible, covering the angles of view offered by multiple large-aperture, fixed focal length lenses.
• HSM (hypersonic motor) delivers high AF speed and extremely quiet performance. An optimized algorithm offers even smoother automatic focusing, and full-time manual focus override is another key feature.
• The lens incorporates a rear focus system that prevents focus-dependent variation in aberration, making high-level image quality possible throughout the entire image. With their unchanging barrel length, these lenses also enhance balance and stability for the photographer. Furthermore, since the front of the lens does not rotate, polarizing filters can be used with extra convenience.
• A first for the industry, the barrel of the lens features a new TSC (Thermally Stable Composite) that offers minimal thermal shrinkage combined with exceptional hardness. It also offers 25% greater elasticity than polycarbonate. Since its thermal shrinkage is low, TSC matches well with metal parts, further contributing to the high-precision construction of the lens. TSC also makes possible slimmer forms for parts like zoom rings and scaling rings
• The brass mount combines high precision with rugged construction. Its treated surfaces and enhanced strength contribute to the exceptional durability of the lens.
• Specifications
  Lens Construction 17 elements in 12 groups
  Minimum aperture F16
  Filter size 72mm
  Angle of view (35mm equivalent) 76.5° – 44.2°
  Minimum focusing distance 28cm
  Dimensions (Diameter x Length) 78mmx 121mm
  Number of diaphragm blades 9 (Rounded diaphragm)
  Maximum magnification ratio 1：4.3
  Weight 810g