Olli Salonen Reviews Sigma 18-50mm Lens
Finnish photographer Olli Salonen has reviewed the inexpensive Sigma 18-50/3.5-5.6 DC lens. This is designed for digital SLR cameras and has a smaller image area than normal lenses, so it can’t be used with full-frame SLRs. It offers a usable focal length of around 28-80mm (depending on the crop factor of your particular DSLR) and costs a mere ?100 in the UK (found via digicamera.net).
“Sigma introduced this digital-only lens in the late 2003 and it resembles closely the Canon’s 18-55 EF-S kit lens, that is sold with the 300D. Sigma 18-50 however is not an EF-S lens, but it will fit all Canon EF (of course there also Sigma, Nikon and Pentax mount versions) compatible bodies. Image circle of this lens is smaller than normal, as it is intended for cameras that have a crop factor of 1.5x or higher. Therefore you cannot use this lens on a full frame camera without significant vignetting.”