Canon's lightweight 400mm f/4 — DO II with diffractive optics reducing weight by 30% vs conventional.
The Canon EF 400mm f/4 DO IS II USM launched in 2014 as a revolutionary super-telephoto using second-generation Diffractive Optics (DO) to dramatically reduce size and weight. At 2100g — 30% lighter than a conventional 400mm f/4 — it changed what was possible handheld.
Optically excellent — the DO II solved the flare issues of the earlier DO technology. Sharp throughout with excellent contrast. IS provides 4 stops of stabilisation. Ring-type USM for instantaneous AF. The weight savings made handheld 400mm f/4 genuinely practical.
Canon EF mount with 52mm drop-in filter holder. 2100g — dramatically lighter than 400mm f/2.8 at 5370g. Full weather sealing. Green DO ring. 1.4x and 2x extender compatible. Minimum focus distance 330cm. L-series build quality.
Available used at professional to luxury prices — the weight savings command a premium. The green DO ring is distinctive. The DO II technology was genuinely successful — no flare issues of the earlier generation. For wildlife and sports photographers who need 400mm f/4 handheld capability.