SUMMARY
Launched in 2001, the Canon EF 400mm f/4 DO IS USM was a groundbreaking telephoto lens featuring Diffractive Optics (DO) technology, making it significantly smaller and lighter than comparable lenses. Despite its advanced capabilities and L-series build quality, it was distinguished by a green ring instead of the traditional red. The DO element corrected aberrations and offered substantial size and weight savings without compromising image quality. However, high manufacturing costs and a steep price point of $6,899 led to low demand, and Canon only produced three EF-mount DO lenses before discontinuing the line, shifting focus to RF mount lenses.
TAKEAWAYS
Canon's EF 400mm f/4 DO IS USM (2001) pioneered Diffractive Optics for compact, lightweight telephoto lenses.
DO lenses offered significant size and weight advantages over conventional lenses.
High manufacturing costs and a premium price led to low demand and discontinuation.
Only three EF-mount DO lenses were released between 2001 and 2014.