>> Chip Stratton <cstrat@xxxxxxxxxx> wrote:
>>
>> Yes, the lens anyway. These used a well known Australian lens coating
>> technology called "Vegemite". Our Down Under list members could
>> probably
>> elaborate.
>>
>
>Yes, the vegemite coating works in a different way to normal anti-reflection
>coatings. The principle is that vegemite absorbs all visible light
>allowing none to
>be transmitted or reflected, it is very efficient at eliminating lens
>flare (or flair), but
>not so good at allowing the lens to actually form an image. Experiments
>are still
>underway evaluating the performance of vegemite in the microwave, infra-red,
>ultra-voilet and x-ray parts of the electromagnetic spectrum. Lenses
>coated with
>vegemite are now being commonly referred to as "stealth" lenses.
>
>
>Wayne Harridge
Yes, the earlier vegemite coatings can be recognised by the deep brown
reflections while the later, post-Kraft offerings can reflect green as
well (lower salt, more mould, I believe). There has also been some
experimentation with multicoating using 'cheese and vegemite' layers but
this is highly susceptible to fungus attack and invertebrate infestations.
There is some transmission in the range higher than 800nm but long
exposures are required to make it acceptable - about 20 years on average.
Apart from that, it is most useful in the ultra-toilet end of the spectrum.
Boots is a chain of Brit chemists with a habit of selling their own generic
brand goods. The projector could be anything, rebadged.
AndrewF
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