The EF 24mm f/1.4L USM (Ultrasonic Motor) lens, built for use with Canon EOS system cameras, is constructed completely from lead-free glass. It's the first EF lens to include Replicated Aspherical and Ultra-low Dispersion lens elements. The former works to suppress image distortion and spherical aberrations (curvature of field), while the latter dramatically reduces lateral chromatic aberrations which are often observed with wide-angle lenses (color fringing). The result is a remarkably high-resolution, distortion-free image over the entire focusing range of the lens, which is 9.84 inches to infinity.
The EF 24mm f/1.4L USM's fast aperture enables photographers to realize outstanding image quality even under extreme lighting conditions, while providing an opportunity for faster shutter speeds under normal lighting conditions. Additionally, Canon's exclusive ring Ultrasonic Motor delivers high-speed, silent auto focusing with full-time manual focus override and smooth operation. Another plus: since the front lens group is fixed and doesn't rotate during focusing, polarizing and special effects filters don't need to be adjusted after focusing. This enables photographers to concentrate on their subjects without the worry of altering the lens' filter position before taking the shot.