Long focal length and compact size
The EF 100mm f/2 USM has a large maximum aperture, but is still relatively compact. The 100mm focal length lets photographers maintain a comfortable working distance from their subjects, and also helps to compress perspective. Sharp, crisp pictures are obtained at all apertures throughout the range.
Large f/2 aperture
A large maximum aperture of f/2 provides outstanding speed for low-light shooting, without the need for flash. Shooting at such wide apertures also throws the background out of focus, placing more emphasis on the subject.
Smooth background blur
A virtually circular aperture diaphragm gives out of focus regions a softer, more uniform feel. Sharp foreground objects stand out against a smooth blurred background.
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.
Super Spectra coating
Super Spectra coatings ensure accurate colour balance and enhance contrast. They also reduce flare and ghosting – a common problem caused by light bouncing off a camera's sensor.
Integration with E-TTL II flash metering
The lens passes distance information back to a compatible EOS camera's E-TTL II flash system to ensure optimal flash metering."