Recently I compare the resolution of tis lens with the other lenses I have (Tamron 17-50 and Tamron 70-200). One of the measurement that I made was the amount of sensor pixels per 1 mm of actual target (same for all shots and lenses). I use Sony alpha 350 camera.

light weight

Shorter focal range that annonced (18-140 mm); backfocusing; slow

The pictures below illustrate the focal length range from wide to telephoto (on Nikon DX format, 1.5x).

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

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

I had a non OS Sigma 18-200 and it was a nice little walk around lens. Took very nice shots with my Canon XTi. I upgraded to the OS version to get the OS function. It seems to work well – probably provides me with 2-3 stops performance and saves a lot of shots for me in less than bright light.

OS; wide range zoom; low cost; small size; good build

Corner softness

Sometimes we are joking about a hypothetical 18-300mm f/1.8 to meet all our photographic needs. Well, we aren't quite there yet nor will we ever see such a lens on a DSLR but the manufacturers are at least scratching this focal length range with some 18-200mm variants and the Sigma AF 18-200mm...

Features a pair of sensors that compensate for camera shake and automatic detection of camera movement when panning...

Excellent resolution for this type of lens; OS; price

Too much chromatic aberration

The OS suffix on this lens stands for Optical Stabilisation, which features a pair of sensors that compensate for camera shake and automatic detection of camera movement when panning.

Excellent resolution for this type of lens; OS; price

Too much chromatic aberration

Recently I celebrated my 50th birthday and my lovely wife gave me &#147carte blanche&#148 (well at l

Price; versatility; macro capability

speed; no image stabilization (yet

Unsurprisingly a lens with this kind of focal range is rarely going to perform as well as one with a shorter range, but we were impressed overall by the results possible. Certainly unless you're into extreme wide or telephoto work, or demand the ultimate quality, you could really be very happy with...

Highly versatile 11.1x zoom range; Great value; Relatively small and light - great travel lens; Polariser-friendly internal focusing

Tamron version very similar; Pricier Nikkor version has anti-shake; Pricier Nikkor version is optically faster; Pricier Nikkor version has better build quality

Although Sigma released their first lens with a built-in Optical Stabilizer (OS) system in the spring of 2004, the company employed this technology in only one pro-grade lens, the 80-400mm f/4.5-5.6. That has changed with the introduction of a more compact/affordable (digital-only) 18-200mm OS zoom.