9 out of 10 points and recommendedSharp at all focal lengths, little distortion at 20mm , excellent build qualitySoft wide open, quite big
Having owned this lens for a year now and having read all the reviews posted on other sites I feel this lens has been overlooked somewhat due to it not being designed for an aps-c sized sensor.reviewed December 27th, 2006 (purchased for $500)
The lens is solidly built with a quality feel to it. I find the camera performs best between F5- F8 but is usable wide open in some instances. Its focusing is not the fastest in the world due to having no HSM and can be discrbed as a little tinny. It however is accurate in good lighting and performs well enough.
The sigma is somewhat of an enigma lens to me, it has so much going for it but i tend not to rely on its fast aperture. It performs best when used for landscapes, architecture and outdoor activities. For low light indoor work i usually rely on primes much more.
This is my jack of all trades lens and finds itself my most used outdoor lens. I would rather have use of the fast aperture in emergency situations then the extra 3 mm of the equivilent canon 17-40F4L. It is a sharper lens at f4 and displays no vignetting or distortion at 20 mm on my APS-H (1D) camera.