The Canon EF 70-300mm f/4.5-5.6 DO IS USM Lens is a relatively compact telephoto zoom offering superior maximum-aperture performance across its entire focal length range.
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 ring-USM motor instead of the lighter, slower, and less costly 'micro-USM' motor.