<<ED glass, to my understanding, reduces flare, ghosting and perhaps some
other undesireable traits inherent in lens designs that have a large number
of elements, such as zooms and long teles.>>
I was under the impression that ED glass was only to correct the focusing
points of all color wavelengths. At long focal lengths using uncorrected
glass, various wavelengths (colors) are not focused at the same point,
resulting in an unsharp image with color fringing. ED glass corrects this.
Flare and ghosting are more dependent on the quality/effectiveness of
multicoating and the number of lens elements (as well as other factors,
like if a light source is in your picture, if you are using filters etc.).
<<Hope this clears things up a bit. BTW, Nikon is not the only lens mfr to
use "ED" type glass. I believe Sigma refers to this type of glass as "LD"
in thier lenses.>>
Minolta, Tokina and Sigma all have "APO" glass, Tamron has "LD" glass,
Canon has "L" glass and Nikon has their "ED" glass. They all are
expensive, high quality optics that correct for the aforementioned color
dispersion inherent in long focal lengths.
Dan Nelson
