[Leica] Re: UV Ghostless filters

["A.H.SCHMIDT" <horsts@primus.com.au>]

At the time, when the Pentax Spotmatic was released, Pentax advertised a Ghostless
UV filter.

This filter did not have a flat ground glass, but it was curved. A similar curve
like the front element of a lens. Pentax in their leaflet says:   "The Ashai
Pentax Ghostless Filter is a breakthrough in filter design. With this curved UV
filter, the image light reflected back to the Ghostless filter and retransmitted
through the lens, forms a duplicate image in the air, thus eliminating a ghost
image on the film plane."
    (Reflection from the film surface, forwards back through the lens on to the
back filter surface > my own explanation when looking at the diagram <)

When I bought my first Spotmatic with the 50mm f1.4 lens, I also bought a couple
of those filters. I left this filters always on this lens and also later on my
Program-Plus with the same opening lens (Multycoated by then)  .The reason I left
the filters on, was because of the extremely rough treatment this cameras get.
(Hiking in the bush, going down old mine shafts and climbing up and down gullies
and ravines. There is often a lot of mud and moisture involved, and the filters
actually protect the lens. (the only times I use a UV filter).

I like to say, this filters really seem to work. I never encountered any ghost
images when using them. There seems to be no visible degrading of the image.

Pentax does not sell those filter anymore. Do any of you have an idea, why this
idea was not further used and developed.. Did I only imagine, that this filters
don't degrade the image?.

There must have been some reason why they have been discontinued. But what?.
If any of  you know some more about this, I would be interested to hear about it.

Regards, Horst Schmidt