WHAT YOU SHOULD KNOW:
Like Sigma's other DC (for Digital Camera) lenses, the 18-125mm f/3.5-5.6 is mountable only on DSLRs with APS-scaled image sensors. (You'll get severe edge vignetting on a 35mm camera.) This $269 optic will be available in the Olympus E-series mount, the most affordable lens for Olympus E-1 and Evolt owners.
Several ounces lighter and about a half inch shorter than typical wide-tomoderate- tele 35mm zooms. Features distinctive matte-black crinkle finish except on the zoom and focus rings, which are covered in matte-black ribbed rubber for extra traction. Well-damped focusing ring is unusually shorttraveling for fast manual focusing. A zoom lock secures the lens in its 18mm setting. Scales are large, legible white-on-black.
IN THE LAB:
SQF data show excellent sharpness and contrast at the three tested focal lengths. We found noticeable barrel distortion at 18mm (1.05%), and noticeable pincushioning at 50mm (0.92%) and 125mm (1.06%). Light falloff disappeared by f/8 at all focal lengths. Close-focusing capability was significantly better than Sigma's published specifications. Sigma claims close-focusing to 19.6 inches; we focused down to 16.9 inches (at all focal lengths). Our tighter focus allowed better magnification power, with test results showing a maximum magnification ratio of 1:4.5 instead of Sigma's 1:5.3 (at 125mm).
A good DSLR zoom for the money.