Even though Aero Bright Coating had superior anti-reflection performance, its nano-order, porous structure has a very delicate coating structure that can be easily damaged by abrasions or scratches. Because of this, its application was limited to a small selection of lens surfaces. It also wasn’t suited for mass production because of restrictions faced in the production process. It therefore could be applied only to rather high-priced models.

To resolve this setback, PENTAX set out to further upgrade its multi-layer coating technology — something indispensable in optical glass — and achieve an optical performance close to that of Aero Bright Coating. Compared with a conventional seven-layer coating applied by a vacuum evaporation process, the new HD Coating forms an eight-layer coating with a uniform layer thickness, created by a high-precision, ion-assisted evaporation process. This is further reinforced by a ninth coating added to the outermost layer by a vacuum evaporation process.

The graph above demonstrates the unevenness in coating layer thickness generated by different coating processes. The ion-assisted evaporation process used for HD Coating has a larger number of samples with zero deviation than the vacuum evaporation process. It also shows a smaller deviation from average thickness.

Because this new coating process minimizes the unevenness in layer thickness created during the coating process, it can improve the overall optical performance of nine-layer HD Coating. Thanks to a higher packing density, it also forms an extremely solid coating layer, making it possible not only to improve lens quality, but also to enhance its applicability across a wider range of lens surfaces and imaging products.

HD Coating demonstrates exceptional anti-reflection performance, far superior to that of the conventional multi-layer coating but also close to Aero Bright Coating — PENTAX’s top-grade lens coating — in the visible ray range (400 to 700 nanometers).

PENTAX intends to expand the HD PENTAX-series lens lineup featuring high-performance, cost-efficient HD Coating.

Since its launch as a lens for use with 35mm film-format SLR cameras, the smc PENTAX-FA 35mm F2AL has become a long-selling, multi-application wide-angle lens because of its exceptional resolving power, even after cameras became digital.

In recent years, the number of heavy, high-performance lenses has increased to accommodate higher-resolution digital cameras. The HD PENTAX-FA 35mm F2, however, retains the well-conceived optical design and compact dimensions of its base model, while also being remodeled to deliver higher performance through a complete review of the entire lens coating process.

By applying the latest, high-performance multi-layer HD Coating, the lens delivers a high-resolution, high-contrast image that is sharp and clear even at the edges.

What are the benefits of HD Coating?
The graph below demonstrates the reflectance of the old and new FA 35mm F2 lenses on the identical lens surface. The HD PENTAX-FA 35mm F2 assures a better anti-reflection performance over the visible ray range (400 to 700 nanometers).