Re: [Leica] Re: Flare with 28mm f2.8 PC SA lens

[Jim Brick <jim@brick.org>]

As I've preached a thousand times before, UV filters are useless. What
happened to you is, even though the sun was outside the frame, it still hit
the surface of the filter. When direct sun hits a filter (any filter), you
will get flare. What you did was simply render the exquisite front coating
of your 28PC useless. Front lens surfaces are meticulously prepared to kill
flare. Filter surfaces are not. I have a 28PC and the huge round sunshade
does not cut-off the sun which is just out of the frame, as does the square
shade for the 21, 24, & 28 lenses.

Jim

At 01:51 AM 1/20/98 -0500, you wrote:
>
>About 10 days ago I was shooting in Manhattan in  Lincoln Center using my
>R5(shame on me for not having Rn with n>5) with  either the 28mm f2.8 PC SA
>lens or 21mm f4 SA(Super-Angulon) lens. Sunshades were attached to the
>lenses; the PC also had a B+W uva drop in filter held by the sunshade. There
>was bright sunlight  at a low angle, typical to  the winter sun about two
>hours from sunset. There is a lot of glass  covering the  Lincoln Center
>buldings.
>I took consecutive pictures of  the same section of Philharmonic Hall with
>both lenses. The sun was outside the frame. The photo taken with the 21mm
>lens was free of flare at f8. On the other hand, the shot with the 28mm
>PC(raised to one-half of its full extension), exhibits the classic features
>of flare at f8; typically the contrast is lost in the area and several ghost
>images of the diaphragm appear in the view.  Here are some questions:
>         1.  Have you experienced  that flare/ghosts  are more prone   to
>occur with PC lenses than with standard wide angle ones?
>          2. Is there something specific to the PC SA  design  that would
>create the problem?
>          3. Would the drop in filter with its 2 extra glass surfaces  cause
>the flare/ghosts? This may be inconsitent with 5 ghosts of the diaphragm.
>Note that the reflections of the sun by the glass surfaces will act as a
>light source. Thus I would like an explanation for the relative immunity of
>the 21mm lens to flare /ghosts in  comparison with the 28mm PC lens.
>Any comments are welcome.
>
>
>           Andrew Jordan
> 35 miles south of LEICA USA
>