Sigma 18-35mm F1.8 DC HSM A Sigma Fit

To achieve a wide zoom lens with a maximum aperture of f1.8, various technical problems need to be overcome. As the aperture value gets larger, the depth of focus becomes shallower, thus it makes the lens design extremely complicated in order to compensate for various distortions, such as spherical, axial chromatic and astigmatic aberration along with curvature of field. In order to compensate for astigmatic aberration across the entire focal range, we have relied on the experience and know how gained when designing our super wide angle zoom lenses such as SIGMA12-24mm F4.5-5.6 II DG HSM and SIGMA 8-16mm F4.5-5.6 DC HSM. In addition, the technological innovation at our Aizu factory also contributes to better lens production. It has enabled us to develop a wide glass-molded aspheric lens, and the incorporation of SLD (Special Low Dispersion) glass has optimized power distribution of the optical elements and compensated for various aberrations as well as curvature of field at the widest angle. Thanks to our knowledge of lens design accumulated over a long period of time plus the latest lens manufacturing techniques, SIGMA has finally made the dream of a zoom lens with F1.8 throughout its entire focal range come true.

Convenient handling is achieved by incorporating internal focusing and zooming which prevents any change in the length of the lens when focusing and zooming. It is possible to use a specialist filter, such as a Circular Polarizer, as the front part of the lens does not rotate.

Flare and ghosting were thoroughly measured and monitored from an early stage in the lenses development to establish an optical design which is resistant to strong incidental light such as backlight. The Super Multi-Layer Coating reduces flare and ghosting and provides sharp and high contrast images even in backlit conditions. Attaching the matched petal type hood, which is supplied, will provide extra protection from flare and ghosting.

With a minimum focusing distance of 28cm and a maximum magnification ratio of 1:4.3, this lens is excellent for close-up photography.

The HSM (Hyper Sonic Motor) ensures a silent, high-speed AF function. Optimizing AF algorithm, smoother AF is achieved. It also enables full-time manual focusing capability which allows sensible focus adjustment by simply rotating the focus ring.

The 9 blade rounded diaphragm creates an attractive round bokeh at large-aperture settings.

The new product lines incorporate rubber for the attachment part of the provided lens hood. For better usability, the designs of the lens cap and AF/MF changeover switch have been improved. In order to ensure high accuracy of the product, all metallic parts and the new compound material, TSC (Thermally Stable Composite), which has a high affinity to metal parts, are housed internally. On the lens barrel, the last three digits of its release year are engraved so the lens can be identified according to the year of its launch.

This lens incorporates a brass made bayonet mount which has both high accuracy and durability. A special treatment to reinforce its strength is applied to the surface giving it greater strength and making it highly resistant to long-term use.

Based on these new lines, we have developed special software (SIGMA Optimization Pro) that can update the lens firmware and adjust parameters such as focus.