Wasn't it Chris Huff who wrote:
>In article <38c2577b@news.povray.org>, "PatchWerk" 
><blu### [at] hotmailcom> wrote:
>
>> ...it does indeed work by an interference process, and it is indeed 
>> the very process we call iridescence... although the incoming 
>> (refracted) light remains largely unaffected, as the multiple glasses 
>> inside the lens seem to cancel each other's color out.
>
>That would be for achromatic lenses, then. I have seen this iridescence 
>on the lenses of pretty cheap cameras, which would probably not have 
>achromatic lenses. The effects from the iridescence are probably just 
>too small to notice.

Yes. I'd guess that the purpose of an antireflective coating is to
increase the amount of light that enters the camera. It's not possible
for the interference process to achieve this equally across the
spectrum, so the lens manufacturers choose to maximize the boost in the
yellow. The purpleness of the reflection would be a side effect of less
yellow being reflected.

-- 
Mike Williams * ##
Gentleman of Leisure

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