My most wanted list, anything more to add?

[Daniel Browning]

Only problem with it seems to be the DO part....BTW, is there something inherently screwed about 'Diffractive Optics'?

I wouldn't put it that way. It's a really neat technology for reducing size and weight. Canon says the 400mm f/4 DO is 27% shorter and 31% lighter than a non-DO 400m f/4 would be.

What is that anyway? Last thing I heard, lenses worked by refraction.

The EF Lens Book says a diffractive optical element has a diffraction grating which stands 10 microns high in a concentric circle made by a 3D ultra-high precision micro machining tool which could be controlled on the order of several nonometers. Wikipedia says the chromatic aberration produced by DO lenses is opposite in direction to that produced by refractive lenses, and so the coupling of a diffractive element and a refractive element can effectively cancel chromatic aberration.


When you look at results of DO lenses vs. normal lenses, it becomes clear that DO only makes sense if you need it shorter, lighter, and you're willing to pay for it in the form of cold hard cash and lower image quality.

why bother DO if IQ is gonna be
affected.

Because sometimes, weight and size matter more than cost and (certain levels of) image quality.

is canon making any
profit out of its two DO lenses?

I would guess that they are.