Conclusion - Pros
- Huge 11x focal length range, ideal general purpose and travel lens
- Relatively low chromatic aberration
- Low distortion (for a superzoom)
- Reasonably effective optical stabilization system, 2.5 - 3 stops benefit
Conclusion - Cons
- Very inconsistent sharpness through the zoom range - extremely soft at 80mm
- Soft corners at all focal lengths
- Occasionally indecisive autofocus
- Slightly less resistant to flare than its more recent competitors
The 18-200mm F3.5-6.3 DC OS HSM is on the face of it an ideal 'do-it-all' travel lens; the 11x zoom range, image stabilization and useful close focus distance combine to give great operational flexibility. But of course this versatility comes at a cost, as optical compromises must necessarily be made to provide such a long range in a single lens. And Sigma's designers appear to have chosen a set of compromises somewhat different to those made in competing lenses, giving their 18-200mm its own character and attributes.
Most interestingly, this is a lens which appears to concentrate on minimizing distortion and chromatic aberration rather than maximizing sharpness. This immediately means it won't win the favor of a certain type of resolution-obsessed photographer, who will look on its inconsistent sharpness (and indeed substantial lack of it at mid-telephoto focal lengths) with displeasure. But for users with less lofty aims - perhaps making ordinary postcard-sized prints, sharing reduced-size versions of their pictures on the internet, or viewing their images on the computer or TV screen without zooming in to scrutinize every minute detail - it's sharp enough, and for such purposes its virtues of relatively low distortion and chromatic aberration will shine through. In this regard it's important to realize that certain lens attributes - severe barrel distortion at wideangle, for example - have the same negative impact on a print whether it's 6" x 4" or 36" x 24", and that high levels of color fringing can have a negative impact at print sizes smaller than those needed to reveal those lower levels of sharpness. So Sigma's approach will potentially pay dividends for the casual vacation photographer looking to use the images straight out the camera with no post-processing.
However the Sigma is in some other areas a slightly sub-par performer; its optical stabilization unit doesn't provide quite the same level of benefit as the latest, very impressive systems in the Canon 18-200mm EF-S F3.5-5.6 and Tamron 18-270mm F3.5-6.3 Di-II VC. The F6.3 maximum aperture at 200mm also compromises autofocus performance (in terms of accuracy and consistency) a little when compared to the aforementioned Canon and the Nikon AF-S 18-200mm F3.5-5.6G VR DX. On the other hand, it's also substantially cheaper than any of these lenses.
Overall, then, this isn't a lens for pixel-peepers who above all else demand critical corner-to-corner sharpness in every shot. But for more normal users looking for a versatile, all-in-one travel lens within a budget, and who'd prefer to while away their evenings looking at and sharing their images rather than post-processing them, it fits the bill just fine. And we're looking forward to seeing what Sigma brings to the party with the upcoming release of its new extended-range superzoom, the 18-250mm F3.5-6.3 DC OS HSM.
Rating (out of 10)
|Ergonomics & handling||8.0|
Recommended (with reservations)
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Sigma 18-200mm F3.5-6.3 OS Review Samples