Sigma 28-105mm f/3.8-5.6 Aspherical IF — autofocus standard zoom for 1990s SLR camera systems.
The Sigma 28-105mm f/3.8-5.6 Aspherical IF followed in the early-to-mid 1990s as an autofocus standard zoom, built for the new generation of electronic SLR bodies from Canon, Nikon, Minolta and Pentax rather than older manual mounts.
It covers 28-105mm with an aspherical element and internal focusing, features aimed at controlling distortion and speeding autofocus compared with Sigma's earlier manual UC zoom of similar range. Sigma sold it in autofocus fittings including Canon EF, Nikon F, Minolta A, Pentax K and Sigma SA mounts.
The aspherical design curbs barrel distortion at 28mm better than the manual-focus UC predecessor, though the modest f/3.8-5.6 aperture still limits low-light and shallow-depth work compared with faster contemporaries.
On the used market it sells for very little alongside older film SLR kits. Test autofocus operation on the matching body, listen for a quiet focus motor, and check the aspherical front element for scratches or coating wear.