The idea behind multi coatings (MC) is not to magically transform the light in
some
way as with a filter. For MCs to have the intended effect they must all be
combined together on the same surface. Who is Mr Carrington? Is Alexander
perhaps
referring to Michael Covington?
The main purpose of MC is to reduce the amount of light reflected off a lens
elements surface. The light reflected off elements surfaces is a problem
because
most lenses, especially zooms, contain numerous elements and therefore numerous
surfaces - ignoring cemented elements.
If you can imagine light entering a lens through the front element, after
passing
through it then encounters the front surface of the second element. Most of
the
light passes through, however a small portion is reflected back at the
underside of
the the first element. Some will pass through, but again some will be reflected
back
into the lens. Some of this may well pass through all subsequent elements and
reach
your eye or the film and contribute to the final image in the form of lens
flare.
This process can happen for all the elements. So the main purpose behind MC is
to
reduce, as much as possible, the light reflected off an elements surface.
Multiple
coatings are employed because they can reduce reflections more than single
coatings
(SC).
A beneficial side effect of MC is that the total transmission of light through
the
lens is maximized.
Now sticking an MC filter on the front of a lens is not going to magically
transform
the coating on every element in the lens to which it is attached. In fact, it
could
be argued that it might increase flare compared with an SC filter because
slightly
more light passes through into the lens ;-)
Giles
c.e. packard wrote:
> I agree with Mr. Carrington. If the light is travelling through more
> than one lens coating , albeit on the lense or filter, couldn't one
> agrue that the light is passing through "multiple" coatings?
>
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