Sigma's 17-35mm f2.8-4 EX is one of the EX Series lenses. It combines a fast f2.8-4 maximum aperture with ultra wide angle zoom lens of 17-35mm. It incorporates aspherical lens elements in the front, as well as rear lens groups, to correct spherical aberration. It also incorporates internal focusing to prevent deterioration of the optical quality at close distances and to eliminate rotation of the front barrel during focusing. A "perfect hood" is provided. The lens materials used in this new lens are lead and arsenic free ecological glass.
Aspherical lenses
Lens elements that are not spherical can reduce the total number of elements required in a lens design. They can deliver better performance while reducing weight and size. Aspherical lenses maximize optical performance while minimizing lens size and weight. Aspherical lenses help reduce some of the problems usually associated with wide angles and zooms, such as lens flare and edge distortion. They also help deliver higher quality telephoto images.
Specifications:
- Lens Constructions: 14 groups, 15 elements
- Angle of View (Diagonal): 103.7º-63.4º
- Number of blade in diaphragm: 8
- Minimum Aperture: f32-45
- Minimum Focusing Distance: 19.7 inches
- Magnifications: 11.5x
- Filter Size: 82 millimeters
- Dimensions (Dia x Length): 3.5 by 3.3 inches
- Weight: 14.1 ounces
Product Description:
17-35mm F2.8-4 EX DG ASPHERICAL HSM is specially designed to suit the characteristics of digital SLR cameras. This lens has a compact dimensions that features overall length of 86.2mm/3.3in. SLD (Special Low Dispersion) Glass is used for effective compensation of color aberration. Two pieces of molded glass aspherical lens elements offer excellent correction for distortion as well as all types of aberration.Excellent optical performance was realized both for Digital SLR cameras and film SLR cameras.It has a minimum focusing distance of 27cm / 10.6in. at all focal lengths, and maximum magnification ratio of 1: 4.5. This super-wide angle lens' useful range of view is very convenient for close-up photography. Sigma, Nikon and Canon are equipped with Hyper Sonic Motor (HSM). It is easy to revert to Manual Focus by simply turning the focusing ring and overriding the AF.An inner focus system provides high performance and convenience. The inner focus system allows the lens to be focused without having to rotate the front of the lens, so the lens accepts a Petal-type hood and it is also easy to use a circular polarizing filter.An inner focus system provides high performance and convenience. The non-rotating lens barrel perfectly suits the matched petal shaped lens hood.