[filmscanners] Re: HP PhotsSmart - questions

["" <wbgilloolyjr@charter.net>]

I think I knew what you meant, but the lens MUST be coated on any
surface that is in contact with air, front or rear, to be effective.  In
fact, the front surface is the most important as that is where the light
is coming from.  It is unlikely that you'd coat part of a lens and not
the front.

Mr. Bill


Laurie Solomon wrote:
> First, I apologize for taking so long to respond; and second, for some
> terminological misuse on my part.
>
> I probably should have used "Front" and "Rear" surfaces of the lens element
> rather than "inside" and "outside" surface.
>
> What I was trying to say was that the better lens makers may be putting
> their coatings on the rear surface of the lens rather than the front
> surface.  Since the rear surface of a lens element is protected from user
> abuse and cleaning abuse by the user, it is less likely to be effected by
> harsh chemical solutions that are used on the front surface.  Even if the
> rear surface of the lens element is facing the front surface of another lens
> element so as to sandwich the coating between the two lens elements, there
> usually is not a vacuum inside the lens and between the lens elements so the
> internal rear surface of a lens element will still interface with air that
> exists between he lens elements.

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