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Real-life resolution - EF-S 18-200mm IS vs EF-S 17-85mm IS vs EF-S 18-55mm IS   To compare real-life performance we shot this scene with the Canon EF-S 18-200mm IS, EF-S 17-85mm IS and EF-S 18-55mm IS, all mounted on the same EOS 50D body within moments of each other. The EOS 50D was set to its best quality JPEG setting, lowest 100 ISO sensitivity and default processing options. The lenses on each camera were adjusted to deliver the same field of view, and set to f8 in Aperture Priority mode. IS was disabled on each lens, and magnified assistance in Live View used to confirm the focusing.

The image above was taken with the Canon EF-S 18-200mm IS mounted on the Canon EOS 50D body. The lens was set to 24mm f8, and the 50D set to 100 ISO. The exposures were identical with each lens (1/250 at f8) and the crops are taken from the upper left, centre, lower right and left of centre, and are presented here at 100%.

At first glance, the first row of crops, taken from the upper left corner of the image, all appear similar, with all suffering from some visible coloured fringing. Look a little closer though and you'll see differences in the actual colour of that fringing, with the three lenses from left to right exhibiting light red, pink and darker red fringing respectively. To our eyes, the fringing on the EF-S 18-55mm IS is the least offensive, but there's not much in it. The good news is Digital Photo Professional can do a good job at removing these from RAW files. Staying with this cropped area, the EF-S 18-55mm IS has a slight edge in sharpness, while the EF-S 18-200mm IS is fractionally softer than the others, but it's a pretty subtle difference.

Moving onto the second row of crops taken from just above the middle of the image again shows three very similar-looking results. There's little to choose between them here, although again the EF-S 18-55mm IS has a very slight edge in terms of contrast and definition - but again this is serious pixel-peeping.

The third row of crops once again look very similar, all suffering from some softness, with only subtle clues like the colour of the fringing to tell them apart. When evaluating the broader area around these crops though, the EF-S 17-85mm IS enjoyed a slight edge in overall sharpness, with some of the details on the other two models becoming a little softer.

The fourth and final row of crops again look almost identical at first glance, although as above, evaluating a larger area around the cropped portion reveals a slight advantage to the EF-S 17-85mm IS in terms of definition, but again this is very subtle.

So closed to f8, all three lenses perform similarly at this focal length, with little to tell them apart beyond the colour of their high contrast fringing. The EF-S 18-200mm IS may have been a tad softer overall than the others, but it was certainly subtle. We have further real-life comparisons though at their shortest and longest focal lengths and at wider apertures, so to see how the lenses measure-up under these conditions, let's move onto our Real-life Corner sharpness results.