>Hi Winsor:
>
>> I thought the 300/4.5 was built with low dispersion glass which is what APO
>> is all about, making all the colors focus in the same place.
>
>Low dispersion glass is not particularily noteworthy or special. It's just a
>crown glass that is combined with flint glass (high dispersion) to reduce
>chromatic aberration. The 40mm f/2.0 is described as using "low dispersion
>glass," for instance. The 300mm f/4.5 is not claimed by Olympus to be
>apochromatic. As they put it:
>". . . with a combination of high refractive index glass and extraordinary
>partial dispersion glass to greatly reduce chromatic aberrations."
>An APO lens, by definition, has none AT SOME particular focusing distance.
>My take: it's semantic mumbo jumbo that gets us to think there is some special
>glass in there. But it isn't ED (extra low dispersion) glass as Nikon calls
>it, or as Olympus calls it "special low dispersion" glass.
>
>Gary Reese
>Las Vegas, NV
>
Thanks, Gary. This is certainly an area for confusion with all the
advertising/marketing language in the mix. One wonders whether the label
"apochromatic" means anything when it gets to selling a lens. When one
could still see lens reviews with resolution figures, there were some
pretty awful figures on some cheap 'apos'.
Winsor
Winsor Crosby
Long Beach, California
mailto:wincros@xxxxxxxxxxx
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