Fast aperture prime lens The EF 24mm f/1.4L II USM has a large maximum aperture of f/1.4, making hand-held shooting possible in low light. Such large apertures can be used to restrict depth of field, even at such short focal lengths. Circular diaphragm blades result in smooth out-of-focus regions (bokeh). Aspherical and UD elements For optimum visual performance, the lens incorporates two types of special elements: aspherical elements to correct spherical aberrations, and Super UD (ultra-low dispersion) elements to eliminate secondary chromatic aberrations. The result is crisp, high contrast and undistorted image quality all the way across the frame. Subwavelength structure lens coating Canon’s patented lens element coating minimises the ghosting and flare caused by internal reflections within a lens and helps the EF 24mm f/1.4L II USM to deliver crisp, clear images. Ultrasonic focusing A ring-type ultrasonic motor drives autofocus extremely quickly, and in near silence. Excellent holding torque ensures the point of focus is reached accurately, without overshooting. Furthermore, full-time manual override is available, making it possible to adjust focus without leaving AF mode. L-series quality The L-series is Canon's flagship professional lens range, representing the best in precision-designed EF optics. L-series lenses combine superior performance with superlative handling, and are resistant to dust and moisture. Lead-free optics Environmentally friendly, lead-free glass is used throughout the construction of the EF 24mm f/1.4L II USM.