The EF 70-300mm f/4.5-5.6 DO IS USM Lens from Canon is a relatively compact telephoto zoom offering superior maximum-aperture performance across its entire focal length range. It incorporates Canon's DO (Diffractive Optics) and IS (Image Stabilizing) technologies.
The use of Diffraction Optics allows a lens to be shorter, lighter, and of higher image quality than comparable normal optical systems of the same focal length and aperture-while this lens is heavier than the consumer-grade EF 70-300mm f/4-5.6 IS USM lens, it is 28% shorter and uses Canon's very best ring-USM (ultrasonic) motor instead of the lighter, slower, and less costly 'micro-USM' motor.