Pentax HD DA 20-40mm f/2.8-4ED Limited DC WR

This Pentax zoom spans 20–40mm on APS-C cameras with the Pentax K mount. The range runs from a wide view to a normal one.

That suits travel, street photography, interiors and landscapes, with the 40mm end adding tighter framing. Pentax introduced the lens in 2013, so it is an older design. It fits photographers who want one modest zoom for walks and daily shooting rather than a bag of primes.

The main trade-off is the variable maximum aperture, which narrows from f/2.8 to f/4 as you zoom toward 40mm.

At 10 oz (283 g), this zoom is light and easy to carry all day. The body measures 2.8 in (71 mm) across and 2.7 in (68.5 mm) long. Screw-in filters attach at the 55mm thread.

The 20mm end gives a wide view with room for context. Use it for street scenes, small rooms and open landscapes where you want the whole setting. At 40mm, the framing tightens. That end suits portraits with some surroundings, still-life details and everyday scenes that need a calmer perspective.

The maximum aperture changes with focal length. At 20mm, f/2.8 admits useful light for dim interiors and evening streets. At 40mm, the widest setting is f/4, so you will need a higher ISO or a steadier hold in the same light.

Depth of field stays fairly deep at these focal lengths even wide open. The lens therefore records scenes with their context rather than isolating a subject against heavy blur. Nine aperture blades shape the opening as it stops down, which helps keep out-of-focus highlights smooth.

Closest focus sits at 0.9 ft (28 cm), which brings you near enough for tabletop and still-life framing. You can fill the frame with a plate or a small arrangement at that distance. Maximum magnification is 0.2x, so small subjects record at a modest scale on the sensor. The optics specification scores 66 out of 100 on our scale.

Weather sealing guards against dust and moisture, so you can keep shooting through changeable weather on a hike or a coastal walk. A fluorine coating helps water and dirt release from the glass. After a wet outing, a quick wipe restores a clean front element.

There is no built-in image stabilization. For handheld shots in low light, plan on a higher ISO, a steady grip or a tripod. A zoom lock is absent as well. The features specification scores 71 out of 100 on our scale.

The optical unit holds one ED element and one Super ED element. Low-dispersion glass of both kinds helps reduce chromatic aberration, where colours focus at slightly different points and leave coloured fringes along high-contrast edges. Backlit branches against a bright sky show this effect clearly, so the glass matters for landscape work. Focusing is internal, with groups moving inside the barrel, so the lens keeps its length as focus shifts.