HD vs. SMC Pentax-DA 18-50mm F4-5.6

Feature Highlights

At the 2015 CP+ show in Tokyo, Pentax announced several new products. One of those was a new version of the ubiquitous kit lens often packaged with new DSLR cameras.

While not as eye-catching as large and expensive lenses, the new 18-50mm packs a lot of innovative features that help differentiate it from other lenses, both those made by Pentax and from other manufacturers.

The first of these features is the retractable system. While not unique in the industry, it is a first for Pentax. Collapsing the lens makes it 41mm thin, turning it into the shortest APS-C zoom on the market. The retractable system is made possible by an impressive feat of engineering, as illustrated by this image of the lens cut in half.

When extended, the inner workings of the lens resemble other classical designs. When collapsed, the lens gets as thin as it can possibly be. Except for the gaps created by the different curvatures of the glass elements, there is absolutely no empty space inside the barrel. The rear glass element even moves slightly towards the back, protruding a bit more than when the lens is extended. The lens still manages to preserve its weather resistance even with the retractable system.

Another feature is the use of focus-by-wire, which will be discussed more at length on our focusing page.

The lens also uses a DC motor for faster and silent focusing. DC motors are found in most new lenses, but so far DA L lenses (such as the 35mm f2.4 and 50mm f1.8) still relied on the older screw-drive mechanism.

This new kit lens also uses a new optical design. While the older kit lens covered the 18-55mm range, with a largest aperture of F3.5 at its widest angle, the new design limits itself to 18-50mm, and begins at F4. These changes were likely necessary to allow for the retractable system.

Two lenses

In line with their previous strategy, Pentax released two lenses based on their new design.

The first is the DA L version, which is designed for camera kits.  It is currently only available together with the Pentax K-S2 DSLR.  It is the first DA L lens with DC focusing. Thanks to its focus-by-wire system, it is also the first DA L with quick-shift. It uses the classic SMC coatings.

The second is the HD version, using Pentax’s most recent coatings. Apart from the coatings, only the inclusion of a hood and its availability as a stand-alone product mark it as different from the DA L variant. The hood also requires a different lens cap. This lens is the first HD DA lens without a metal mount, using plastic like the cheaper version.  We find this to be acceptable given the light weight of the lens.

Cosmetically, only lettering lets users differentiate between the two lenses. The front shows the whole pedigree of each lens, and the type of coating is clearly marked. The side of the lenses show a small square badge with either DA or DA L printed in black.

Note that the difference in the coatings is visible in the umbrella reflection in the image above.

Summary

Our aberration tests will show if the coatings have a significant impact on image quality. Apart from the coatings, hood, cap and lettering, the two lenses are identical. There is no difference in the build quality, quality of assembly, design, weight, or materials.