The appeal of superzooms is obvious. A single lens like this, which covers a focal range equivalent to 27-300mm, can replace two or even three ordinary zooms. You don’t have to worry about carrying round separate lenses, you don’t have to waste time swapping from one to the other and there’s also less opportunity for dust to get into the camera body and onto the sensor.

At the same time, though, superzooms have some significant disadvantages, including price, weight, image softness, distortion and chromatic aberration. So in any test of a superzoom, these are the first things to check.

It doesn’t take long to find the Sony’s weakness. At short focal lengths the sharpness is good and more or less up to the standard of a kit zoom. By the middle of the focal range, though, the overall sharpness has dropped substantially. The quality starts to pick up if you stop down to around f8 or f11, but wide open at f5.6 it’s very soft. And at the maximum focal length of 200mm, our lens’s definition was, frankly, bad. Wide open, it was so soft it was obvious on-screen without having to enlarge the images at all.

It also suffers from extremely weak edge performance at longer focal lengths, even at smaller apertures. In the centre of the frame, the quality does pick up when you stop down to f11 or f16 to the extent that pictures do look acceptably sharp, and if you habitually put your subjects in the centre of the frame and never look at the edges, you might be none the wiser. Our chart, though, uses an average of the centre and edge definition, and this lens’s poor edge detail drags down the overall figures.

It’s common for lenses of this type to show some loss of sharpness at their maximum focal length, but these results are poor even by superzoom standards. This makes the price even harder to swallow. The list price has crept up over recent weeks by around £40, thanks no doubt to the global economic situation, and the SRP of £489 is quite a lot of money. If you shop around you can pick this lens up for less than £400, but the same outlets are selling the Sigma 18-200mm, for example, which is also available in the Sony mount, for at least £100 less – and it’s a better lens than this one.

This poor performance is a great pity, because in other respects the Sony 18-200mm isn’t bad. There’s a fair degree of barrel distortion at the widest focal length, as you’d expect, but less pincushioning than usual in the middle and long end of the zoom range. Chromatic aberration is about average for this kind of lens, too.

What’s more, the Sony 18-200mm handles quite well. It’s not that big for a superzoom, with a neat, slim barrel and a good zoom action. The autofocus is quite coarse-sounding and the manual focus ring has a rough feel, but it does have a distance scale and the non-rotating front element means this is a filter-friendly lens too.

It does have a plasticky feel though, and feels cheaper than independent superzoom lenses despite costing substantially more. The lens mount is plastic too, so the cost-cutting is all too obvious. However, the biggest problem with this lens is its optical performance. It’s just not good enough at any price, let alone £489.

Final Verdict Despite its somewhat cheap build the Sony 18-200mm handles well, but it’s crippled by its weak edge performance at medium and long focal lengths 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.