Posted by David Ruether on 12/21/07 18:18

"Spex" <No.spam@ta.com> wrote in message
news:13mnp6n5bpbgi40@corp.supernews.com...

>>> Chromatic Aberration.
>>>
>>> Around contrasty areas you'll see green and purple or blue and red lines
>>> caused by the refracting at different wavelengths. It has always been
>>> there just not as obvious in the low res world of SD.
>>>
>>> Lens can be coated to reduce this but it can lead to ugly bokeh if the
>>> lens is over optimised.

>> It is a lens design (or alignment fault) characteristic, not a matter
>> of coatings...
>> --DR

> That's contrary to Canon's claims of using flourite elements and coatings
> to reduce CA.

You may have misread the literature (or it may have been intentionally
misleading...). The design of the lens, including glass types, shapes,
spacings, and combinations, can/will control the amount of CA
(and linear distortion, sharpness, etc.), but coatings can control only
the lens transmissions/reflections - and you certainly do not want to
filter out the CA colors from the image using coatings! 8^)
--DR

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