The 28-75mm f/2.8 XR Di LD is a wide/standard-range zoom lens thats compatible with both full-frame and crop-frame DSLRs. Its fast and constant f/2.8 aperture allows for great background separation from your subject and makes low-light shooting possible. It features XR (Extra Refractive Index) and LD (Low Dispersion) glass in a 14-group/16-element optical formula. This provides images with high contrast and sharpness across the image plane. By utilizing an aspherical element. the 28-75mm exhibits very little chromatic aberration for high color accuracy. Its internal focus design means the lens doesnt extend during autofocus. and the non-rotating front element allows uninhibited filter use.