[Leica] New Canon Optical Element Design

[Larry Kopitnik <kopitnil@marketingcomm.com>]

Canon has posted to their web site a description of a new kind (new 
to interchangeable lens camera use, anyway) of optical element, which 
they call a "multi-layer diffractive optical element." They say it 
offers superior correction of chromatic aberrations and allows them 
to design telephoto lenses substantially smaller and lighter. They 
describe a 400 mm lens they will show at Photokina incorporating the 
element.

The full description is at http://www.canon.com/do-info/index.html

I know nothing more than what is on that web page, but to someone who 
knows little about optical desing (like me!) it looks impressive. 
Does anyone better versed in optical design (Erwin?) see a downside 
to incorporating such an element in a lens design?

Larry