Zoomed-out to wide angle, the Olympus SP-550UZ delivers fairly good results in its corners with only slight softening when the aperture's wide open. There's a hint of coloured fringing, but it's clearly superior to the Nikon D40's kit lens, although both the Panasonic FZ50 and Canon G7 deliver better-corrected results overall.
Zoomed-in to telephoto, the Olympus SP-550UZ suffers from quite visible coloured fringing, and this is also apparent in real-life examples pictured in our Gallery. All the Olympus results on this page are also slightly lower contrast than the models we've compared it against, although to be fair, none of them come anywhere close to sharing its massive 18x optical zoom ratio. The closest is the Panasonic FZ50, but even its 12x optical zoom can't get as wide as the Olympus. Clearly there'll almost always be some optical compromise with such a huge zoom range, and for the SP-550UZ, it would appear to be coloured fringing, especially when zoomed all the way in.
Note: crop details which appear smaller here are due to them being captured with lower resolution cameras and / or a lens which couldn't focus as close to the chart. In each case though, the crop still represents the extreme bottom left corner of each camera's frame. The Nikon D40 samples show a different portion of the chart because it captures wider 3:2 aspect ratio images, but again the results below still represent the extreme bottom left corners of the frame.