Camera Accessories

The Zuiko Digital 40-150mm f/4.0-5.6 lens was launched at the end of 2006 and is usually offered in twin-lens kits with Olympus DSLR cameras. Claimed as the smallest and lightest in its class, it fulfils the promises of the Four Thirds System in both respects. With a barrel only 72mm long and weighing only 220 grams it covers a focal length range equivalent to 80-300mm in 35mm format.

Optical construction is typical of many tele-zoom lenses, with 12 elements in nine groups. An ED (Extra-low Dispersion) glass element is included to provide high performance combined with portability. High-refractive-index glass elements are used in the optical design to minimise chromatic aberration, coma and image curvature and multi-coatings reduce flare and ghosting in backlit shots.

 
A structural diagram of the Zuiko Digital 40-150mm f/4.0-5.6 lens showing the pisition of the ED element. 

The iris diaphragm has seven blades that close to make a circular aperture and ensure smooth defocused backgrounds at wide aperture settings. Internal focusing allows angle-critical filters to be used without requiring constant adjustments. This lens will focus to 90 cm from a subject at all focal length settings.

Build quality is reasonably good for a mostly plastic lens. (Even the mount is plastic.) The focusing and zoom rings have textured rubber coatings to provide a secure grip. The ridges on the focusing ring are narrower than those on the zoom ring and the ring itself is also narrower. The leading edge of the zoom ring is marked with five focal length settings: 40mm, 50mm, 70mm, 100mm and 150mm. An engraved mark just behind the focusing ring provides a reference for setting precise focal lengths.

Aperture settings range from f/4.0 to f/22 at the 40mm setting and f/5.6 to f/22 at 150mm. As you change focal length, the maximum aperture also changes to f/4.2 at 50mm, f/4.6 at 70mm and f/5.0 at 100mm. Maximum magnification is 0.14x, which is a long way from the true 1:1 macro range.  Neither a distance scale nor indicators for depth of field or infrared adjustment are provided.

Supplied with the lens are a cylindrical lens hood that reverses over the lens when not in use and a clip-on lens cap. A rear cap is also provided, along with a user manual and Olympus Worldwide Warranty Card. A teleconverter (EC-14) and extension tube (EX-25) are available as options. The lens accepts 58mm filters.

Handling
The 40-150mm f/4.0-5.6 lens feels very well balanced on the E-420 body and its size and weight are a good match to the E-420's compact size. Moving through the zoom range requires roughly a third of a turn and we found the markings on the lens barrel corresponded pretty closely with the actual focal length settings.  The front of the lens extends without rotating by approximately 58 mm when you zoom from 40mm to 150mm.

The focusing ring appears to have infinite movement and it was difficult to estimate how much it had to be turned to go from the closest focus to infinity. However, since it can only be used when manual focusing is set in the camera, we feel most users will stick with autofocusing most of the time.

Autofocusing was generally fast and accurate with the supplied lens and the lens covered the full autofocus range in less than a second. We noticed some hunting in low light conditions but none with normal light levels. As expected, hunting was more common with longer focal length settings. We found no tendency for the lens to 'creep' when it was carried pointing downwards. 

Performance
The test lens turned in a competent - but not stellar - performance in our standard set of tests. For a budget-priced lens, it can be considered well up to the standards that typical buyers of Olympus's entry- and mid-level DSLRs would expect for the price. But it didn't quite match the potential of the E-420's sensor.

In our Imatest assessments we found the test lens performed best at wider apertures, tailing off from about f/13 onwards where diffraction began to impact on image sharpness. Interestingly, the 50mm focal length setting gave the highest resolution, and was slightly better than the 40mm setting. And, although resolution was lowest at the 150mm focal length it was not by a huge amount. The graph below shows the results of our tests, based on JPEG images.

Imatest also showed there was little difference between centre and edge resolution at all focal lengths, indicating only a minor edge softening. This edge softening was at its least at the 150mm focal length and negligible at the smallest apertures. We were surprised by the high levels of consistency in our test results for all focal lengths, which undoubtedly results from Olympus's 'designed for digital' approach to lens production. 

We obtained some interesting results in our Imatest tests when it came to lateral chromatic aberration. These tests showed the test lens to be optimised for the 70mm focal length, which is unusual. At the 40mm, 50mm and 100mm focal lengths, chromatic aberration remained within the 'low' band, only moving to the 'moderate' level at 150mm. The graph below shows the results of our tests, with the red line indicating the border between 'negligible' and 'low' CA and the blue line the border between 'low' and 'moderate'.

Vignetting (corner darkening) is seldom found with telephoto lenses and we found no evidence of it with the test lens. Rectilinear distortion was another matter, although it was never enough to affect everyday photography. At the 40mm setting we observed slight barrel distortion, which vanished by 50mm. However, slight pincushioning became evident at around 70mm and increased gradually as the zoom extended to 150mm. At no point was it ever severe.

Flare was generally well handled and bokeh (out-of-focus blur) was good for a lens of this type. The focal length range of this lens will suit subjects such as sports, nature and portrait photography. Some sample images are shown below.

IMATEST GRAPHS

Focal length range: 40-150mm (= 80-200mm in 35mm format)
Picture angle: 8.2 to 30 degrees
Maximum aperture: f/4.0 to f/5.6
Minimum aperture: f/22
Lens construction: 12 elements in 9 groups, including ED Lens Element
Lens mount: Four Thirds System
Diaphragm Blades: 7 (circular aperture diaphragm)
Minimum focus:  90 cm
Filter size:  58 mm
Dimensions (Diameter x L): 65.5 x 72 mm
Weight: 220 grams