Sigma 12-24mm f/4.5-5.6 AF II DG HSM Lens for Nikon Digital SLRs

• Compatible with full frame digital SLRs.
• Ultra-wide 12mm focal length.
• FLD and SLD lens elements.
• Fast and quiet autofocus.

From the Manufacturer --------------------- Ultra wide angle zoom lens compatible with digital SLR cameras with 35mm full frame image sensor. ----------------------------------------------------------------- This ultra wide angle zoom lens incorporates the latest optical design provides superior performance. FLD ("F" Low Dispersion) glass elements, which have performance equal to fluorite, and SLD (Special Low Dispersion) glass elements provide excellent correction of color aberration. Aspherical lenses give advanced performance with a compact and lightweight construction. The Super Multi-Layer Coating reduces flare and ghosting. High image quality is assured throughout the entire zoom range. Incorporation of HSM ensures quiet and high speed autofocus as well as full-time manual focus capability. This lens has superior peripheral brightness and provides sharp and high contrast images even at the maximum apertures. Ultra wide angele zoom: Sigma made it first ------------------------------------------- Sigma designed and produced the first wide-angle zoom lens, the "zoom gamma 21-35mm F3.5-4", in 1979. Sigma has since introduced a number of wide angle zoom lenses. The SIGMA 12-24mm F4.5-5.6 II DG HSM is the successor of the SIGMA 12-24mm F4.5-5.6 EX DG ASPHERICAL / HSM which was launched in November 2003. This ultra wide angle zoom lens is ideal for digital SLRs with a 35mm full frame image sensor and incorporates the latest optical design. Superior image quality ---------------------- The ultra-wide angle zoom lens is possible due to large diameter of the front lens. Four FLD ("F" Low Dispersion) glass elements, which have performance equal to fluorite, and one SLD (Special Low Dispersion) glass element provide excellent correction of color aberration. Three glass mold elements and one hybrid aspherical compensate for all types of aberration and ensure high optical performance. *FLD glass is the highest level low dispersion glass available with extremely high light transmission. This optical glass has a performance equal to fluorite glass which has a low refractive index and low dispersion compared to current optical glass. It also benefits from high anomalous dispersion. These characteristics give excellent correction for residual chromatic aberration (secondary spectrum) which cannot be corrected by ordinary optical glass and ensures high definition and high contrast images. No Super Multi-Layer Coating (left). With Super Multi-Layer Coating (right). Super Multi-Layer Coating ------------------------- Due to the ultra-wide angle, the front of this lens is very large. Sigma's Super Multi-Layer Coating reduces flare and ghosting which could otherwise create problems when extraneous light hits the lens' front element. It also provides sharp and high contrast images throughout the entire zoom range. Superior peripheral brightness ------------------------------ The design of front lens group minimizes light fall off and increases peripheral brightness. Exaggerated perspective ----------------------- The wide-angle of view produces striking images with exaggerated perspective, enabling photographers to emphasize the subject. Compact construction -------------------- Incorporation of four aspherical lenses provides a compact construction with a diameter of 85mm (3.3"), overall length of 4.7" and weight of 23.6oz. The compact construction makes this lens ideal for travel photography. Hyper Sonic Motor Quiet and high speed autofocus ------------------------------ HSM indicates lenses equipped with a Hyper Sonic Motor, driven by ultrasonic waves. Incorporation of HSM (Hyper Sonic Motor) ensures quiet and high speed autofocus, while allowing full-time manual focus override. Inner focusing system --------------------- This lens incorporates an inner focusing system, which eliminates front lens rotation which also minimizes fluctuation of aberration caused by the focusing system Lens Construction ----------------- In a conventional lens, focusing requires an extension of the entire lens or the front lens group. However, to better accommodate autofocusing mechanisms and closeup photography, a need has arisen for lenses that do not change their length during focusing or suffer from focus-dependent variation in aberration. Therefore, Sigma has developed focusing systems that only move elements within the lens barrel. These incorporate smaller and lighter moving lens elements which help improve auto-focus speed. With their unchanging barrel length and small variation in the center of gravity, 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. Specifications -------------- Lens Construction 17 Elements in 13 Groups Angle of View 122 - 84.1 degrees Number of Diaphragm Blades 6 Blades Minimum Aperture (W) F22 Minimum Focusing Distance 28cm / 11in. Maximum Magnification 1:6.4 Dimensions Diameter 87mm x Length 120.2mm / 3.4in. x 4.7in. Weight 670g / 23.6oz. MTF Chart --------- View Larger Image ( https://images-na.ssl-images-.com/images/G/01/electronics/lenses/Sigma/12-24mm/SIGMA_12-24mm_img4_lg._V401491969_.gif )MTF (Modular Transfer Function) is one of the measurements that evaluates a lens' performance, and it contrasts sensitivity at different spacial frequencies. The horizontal axis is in millimeters and shows the distance from the center of the image toward the edges, and contrast value (highest value is 1) is shown in the vertical axis. The readings at 10 lines per millimeter measure the lens' contrast ability (red lines), repeating fine parallel lines spaced at 30 lines per millimeter measure the lens' sharpness ability (green lines), when the aperture is wide open. Fine repeating line sets are created parallel to a diagonal line running from corner to corner of the frame, are called Sagittal lines (S) and sets of repeating lines vertical to these lines are drawn, called Meridional (M) line sets. Distortion ---------- View Larger Image ( https://images-na.ssl-images-.com/images/G/01/electronics/lenses/Sigma/12-24mm/SIGMA_12-24mm_img5_lg._V401491968_.gif )effective distortion: When you take a picture of a lattice pattern, it will appear as the blue dotted line shows. the red line illustrates how the lattice pattern will appear in the actual picture when any lens distortion is taken into account. relative distortion: In this chart, the horizontal axis shows the ideal image height (the distance from the center to the edge of the image [mm]). The vertical axis shows the extent of distortion. The extent of the distortion is represented by how much Y, which is the actual image height, grows (or shrinks) against Y0 which is the ideal image height. Extent of distortion: D[%]=(Y-Y0/Y0)x100 When you take the picture of a square object, if the distortion a show a minus value, the image will be seen as expanded (Barrel distortion). If the distortion a is a plus value, it will be seen as a recessed (pincushi on distortion). When the distortion value is close to 0, the appearance of distortion is very minimal. Vignetting ---------- View Larger Image ( https://images-na.ssl-images-.com/images/G/01/electronics/lenses/Sigma/12-24mm/SIGMA_12-24mm_img6_lg._V401491997_.gif )The horizontal axis shows the image height (the distance from the center to the edge of the image [mm]). The vertical axis shows the a of light in the image (based on the a of light in the image center being 100%). If the peripheral a of light is lower than the center, the four corners of the image will be darker (vignetting).