rkamantas Loc: Beverly Shores, Indiana

Canon EF 70-300 f/4.5-5.6 DO IS USM. Please explain "DO"(Diferactive Optics).... Thanks

traveler90712 Loc: Lake Worth, Fl.

From the Canon site
"Canon’s use of diffractive optics (DO) results in high-performance lenses that are much smaller and lighter than traditional designs. Canon’s unique multilayer diffractive elements are constructed by bonding diffractive coatings to the surfaces of two or more lens elements. These elements are then combined to form a single multilayer DO element. Conventional glass lens elements disperse incoming light, causing chromatic aberration. The DO element’s dispersion characteristics are designed to cancel chromatic aberrations at various wavelengths when combined with conventional glass optics. This technology results in smaller lenses with no compromise in image quality. Canon has also developed a triple-layer type DO lens that uses an advanced diffractive grating to deliver excellent performance, with superior control of color fringing. This configuration is ideal for zoom lens optics and provides significant reductions in size. A good example is the EF 70–300mm f/4.5–5.6 DO IS USM lens, which is 28 percent shorter than the EF 70–300mm f/4–5.6 IS USM lens."

Hope this helped.

f8lee Loc: New Mexico

As I recall from when they put out their first DO lens, the name refers to one of the internal elements being ground in a Fresnel lens kind of manner rather than the typical convex or concave styles, which allows for a much thinner and lighter piece of glass that still bends light to the same degree as a conventional lens does.

imagemeister Loc: mid east Florida

The idea behind it is to reduce the size/weight of the lens while retaining the image quality of a conventional lens. You do pay a premium $ for this ability.......

tradergeorge Loc: Newport, Kentucky

I would be interested in learning more about the principles involved in this. I worked extensively with Fresnel lenses when i was in the Navy. Our application was in optical landing systems, i.e. the "Meatball" Top Gun viewers are familiar with. This, and traffic signals, made use of them to direct light on a particular plane, much like a Laser would but in a much more primitive and "ham-fisted" way.....I can see where these type elements in a camera lens may direct light with a smaller lens, but it would be news to me if they gave anything other than a blurry blob....

Technology marches on, eh?