Archived posting to the Leica Users Group, 2007/03/19
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>The last word from Schneider Optics themselves on the 486 filter......
>----------------------------------------------------
>IMPORTANT NOTE REGARDING WIDE-ANGLE LENSES.
>
>Please note however that, in contrast to
>mass-colored (integrally colored) filter glass,
>the UV-IR barrier filter is based on
>thin-film technology. More than 30 interference
>coatings are vapor-deposited on one side, while
>the opposite side is MRC-coated. In
>wide-angle lenses, the laws of physics lead to
>shallower incidence angles for peripheral rays.
>For geometric reasons these rays have
>to travel further through the interference
>coatings than rays traveling vertically through
>the coatings in the centre of the lens.
>With increasing angle of incidence, this leads
>to a change in light color towards blue. This
>effect can clearly be seen by looking
>at an UV-IR barrier filter from an angle. The
>color of the reflected light changes, with a
>similar effect on the light traveling
>through the filter.
>
>The filter is therefore not suitable for lens
>systems with an angle of view of more than 60?
That was pretty much the point and content of previous posts.
>--------------------------------------------------------
>Guess I was suspicious, right and wrong all at
>the same time. Now to figure out which of the
>Leica lenses have an angle of view of
>more than 60 degrees...... Anyone interested?
Since it's not a sharp cutoff, circumstances such
as subject matter, evenness of illumination and
personal tolerance have a say in this. As
mentioned before, pictures taken with a 28mm and
shorter will generally need a correction, and
35mm is on the cusp. Film and digital are
affected similarly, but digital is easier to
correct.
>If you want the entire specialized word file
>sent to me by Schneider, please email me
>directly.....
>
>Frank Filippone
>red735i@earthlink.net
--
* Henning J. Wulff
/|\ Wulff Photography & Design
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