Short Report: Tamron AF18-200mm F/3.5-6.3 XR Di-II
Get true wide-to-tele performance with this extreme-range zoom designed for digital
Users of 35mm SLRs have long enjoyed extreme-range zoom lenses of 28-200mm and, more recently, 28-300mm. These lenses can be used on digital SLRs, too, but since most D-SLRs have image sensors that are considerably smaller than a full 35mm film frame, these zooms provide a much narrower field of view when used on D-SLRs—equivalent to 42-300mm and 42-450mm on a 35mm SLR.
Now, D-SLR users can enjoy true wide-to-supertele-zoom versatility, thanks to the recent introduction of the 18-200mm zoom. Tamron's AF18-200mm F/3.5-6.3 XR Di-II is an excellent example of the breed. Designed specifically for APS-C-sensor digital SLR cameras (on which it provides the equivalent of a 28-300mm focal length on a 35mm SLR) and featuring a minimum focusing distance of 17.7 inches at all focal lengths, this 11.1x zoom is a versatile tool. In fact, many users of APS-C-sensor D-SLRs will find that this one lens can handle all of their shooting needs.
Along with the advantages of convenience and keeping you ready for just about any photo op that might present itself, the extreme-range zoom means you won't be changing lenses nearly as often, which in turn means less dust on your D-SLR's image sensor—a nice bonus.
The AF18-200mm employs XR (Extra Refractive Index) glass, three hybrid aspherical elements and two LD (low-dispersion) glass elements in its 15-element/13-group design, resulting in a very compact lens (2.9x3.3 inches and 14 ounces) that's well corrected for spherical aberration, chromatic aberrations and barrel distortion. The optical design is optimized for the smaller APS-C image sensors, directing light rays to the pixels more effectively and producing less light falloff at the edges than lenses designed for 35mm SLRs. Multilayer internal surface coatings minimize ghosting and flare, which is especially important for digital SLRs and their shinier-than-film image sensors.