Canon's diffractive optics telephoto — 70-300mm with DO element for compact design and green ring.
The Canon EF 70-300mm f/4.5-5.6 DO IS USM launched in 2004 as Canon's first consumer lens with a Diffractive Optics element, identifiable by a distinctive green ring. The DO element enables a more compact design than conventional 70-300mm lenses.
Optically adequate — the DO element reduced size but introduced a characteristic flare pattern visible in some backlit conditions. IS provides stabilisation. Ring USM motor for fast, silent AF. Good sharpness in the centre but not matching the later 70-300L.
Canon EF mount with 58mm filter thread. Approximately 720g — compact for 70-300mm with IS at the time. Full-frame coverage. The green ring identifies DO technology. Minimum focus distance 140cm. L-series quality build.
Available used at mid-range prices. The DO flare characteristic is the main criticism — visible as coloured rings in some backlit situations. The 70-300mm f/4-5.6L IS USM is optically superior. The DO II versions improved significantly. An interesting technological experiment.