This ultra-wide-angle zoom lens delivers high-resolution, high-contrast images without blurring at the edges, and assures excellent imaging performance in high-grade digital photography, even at open aperture.

It has been developed as model of the new-generation Star (★) series — a lens that provides exceptional image quality to be able to accommodate the super-high-performance digital cameras of the future.
With the introduction of this lens, the high-quality, high-performance Star series now provides a wide angle-of-view coverage —from ultra-wide angle on — with its compact models featuring a large F2.8 maximum aperture, which are exclusively designed for use with PENTAX APS-C-format digital SLR cameras.

In addition to an outstanding dustproof, weather-resistant construction, and -10°C cold-resistant construction, the lens provides a Focus Clamp Mechanism to lock focus at the desired focal point.
It also provides useful features to improve performance and dependability in harsh outdoor conditions: a space specifically designed for wrapping a heating device to prevent dew condensation, and a metallic frame structure to more effectively transmit the heat of the heating device to the lens. These devices greatly improve the lens’s operability when shooting landscapes and starry skies.

Technologies supporting exceptional imaging performance

For a lens to be designated as a new-generation Star-series model, it must clear a number of strict in-house standards. Here are some examples of outstanding optical designs and the advanced technologies which have realized them.

In order to effectively reduce various aberrations, the new lens incorporates an Extra-low Dispersion (ED) glass-molded aspherical optical element, in addition to two ED optical elements and two aspherical optical elements.

MTF (Modulation Transfer Function) is a kind of index used to evaluate lens performance, which represents the extent of subject contrast reproduction as spatial frequency.
The MTF chart here shows the contrast on the vertical axis, and distance from the center of the image on the horizontal axis. For the spatial frequency, 10 lines/mm shows a low frequency, and 30 lines/mm shows a high frequency, resulting in the MTF graph. On the graph, the solid line represents the S direction (sagittal direction and radiation direction) MTF, and the broken line represents the M direction (meridional direction and concentric circular direction) MTF.
In general, a low-frequency MTF is proof of a clear, high-contrast lens, and a high-frequency MTF is proof of a sharp lens with high resolving power.