Apochromatic color correction and an aspherical lens surface are combined for the first time in this lens of this type. Of its five individual elements, two are made of high-refraction glass, while two others feature anomalous partial dispersion. Its brilliance and quality of resolution are exemplary even at full aperture. Light falloff is very low. Its fast aperture for a 90mm lens lets you shoot at relatively short exposure times even in dim light, helping to minimize the effects of camera shake, as when photographing street scenes from a distance.