It’s taken Olympus a while to gather momentum with its DSLRs, but its digital lens range has long been impressive. These lenses are split into three groups: Standard, Pro and Top Pro. The 50-200mm here comes from the Pro group.

And it certainly feels like a professional lens, weighing in at over a kilogram and coming with a rotating tripod mount – with lenses this size you need to mount the lens on the tripod, not the camera.

Olympus doesn’t seem to have made much effort to restrict the dimensions. The focal range of this lens is only a little wider than the Zuiko 40-150mm zoom available as part of the twin-lens kits for the E-410 and E-510, but it completely dwarfs it physically.

In fact, the weight means this is isn’t really a ‘walkaround’ lens. You’re not going to carry it around on the off-chance you might need it. With lenses of this size and weight, you only use them when you need to for specific jobs.

The main point about this lens is its maximum aperture. It doesn’t quite hold the same maximum aperture all the way through its zoom range, but it shifts less than a stop, from f2.8 to f3.5, so it’s almost a constant-aperture zoom.

The Four Thirds system has a 2x focal factor, so this lens is equivalent to a 100-400mm. A 100mm f2.8 is impressive enough, but a 400mm f3.5 is stunning. This easily beats most rival telephoto zooms and is on a par with professional fixed focal length telephotos.

But how does the image quality hold up at these wide apertures? Like other zooms, the Olympus delivers its best sharpness at its shortest focal lengths. At 100mm equivalent, it’s very good wide open and excellent by f8. At 200mm equivalent, it’s slightly softer wide open and, while it’s very good from f5.6 onwards, it never quite hits the same levels of resolution.

The performance at maximum focal length is a little disappointing, though. This lens’s 400mm f3.5 capability is one of its major selling points, but at f4 and f5.6, the results are actually quite soft. At f8 and beyond it’s not bad, but you are losing the benefits of the wide maximum aperture.

It’s unwise to place too much emphasis on resolution tests. In real-world shooting, the Olympus shows a different side. Its images are contrasty and crisp-looking, even at maximum focal length – here, atmospheric haze, subject movement and shallow depth of field frequently take the edge off the maximum obtainable definition anyway. Although the resolution figures might show a drop at 400mm equivalent, the contrast remains high and images look crisp. The other thing that emerges is the total lack of chromatic aberration. Most long zooms suffer badly from fringing at full stretch, but there simply isn’t any with this lens.

Yes, the Zuiko 50-200mm is heavy and specialised, and the sharpness does drop when it’s wide open at maximum focal length. But the pictorial quality of the results remains excellent, and there are none of the aberrations that plague other, less-expensive, long zooms. This shouldn’t be underestimated and it’s at least as important as outright resolution.

Final Verdict Somewhat disappointing at full-zoom, but super-sharp at other focal lengths and totally free of chromatic aberration OVERALL

Our lens reviewer, and technical expert, Rod is a veritable photographic encyclopaedia. His illustrious CV has seen him write for many mags, websites and journals.