[Leica] What is > 60 deg

[robert.rose at mac.com (Robert Rose)]

>From the Leica web site:

Angle of view (Diagonal, horizontal, vertical)

50mm Tri-Elmar-M (47, 40, 27)
35mm Summicron-M (63, 54, 38)
28mm Summicron-M (75, 65, 46)
24mm Elmarit-M (84, 74, 53)
21mm Elmarit-M (92, 81, 59)

So, assuming that the 1.3x factor cuts the angle of view down to the next
higher focal length, we should see the cyan vignetting on the following
focal length lenses:

(Diagonal, horizontal, vertical)
50mm (no, no, no)
35mm (no, no, no)
28mm (yes, no, no)
24mm (yes, yes, no)
21mm (yes, yes, no)
Under 21mm (yes, yes, yes)

In other words, a 28mm lens on the M8 should show some cyan vignetting at
the corners, which is what I find on the TE.  The 35mm setting is barely a
problem, and the 50mm setting is no problem, on the TE.  This confirms the
numbers above.

You would expect cyan problems at the left and right edges of the 21mm and
24mm lenses.

I used a 486 filter on a Nikon 17-55 while shooting snow pictures (do not
ask why).  I got strong cyan vignetting at the corners, and left and right.
Those pictures are now b&w, and that filter now sits on a 70-200
permanently.

Cheers,
Bob
==============

Message: 11
Date: Mon, 19 Mar 2007 07:09:47 -0700
From: "Frank Filippone" <red735i@earthlink.net>
Subject: RE: [Leica] Ir filter and film cameras, take it off
To: "'Leica Users Group'" <lug@leica-users.org>
Message-ID: <014d01c76a30$410e9e40$c32bdac0$@net>
Content-Type: text/plain;    charset="iso-8859-1"

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?
--------------------------------------------------------
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?

If you want  the entire specialized word file sent to me by Schneider,
please email me directly.....

Frank Filippone
red735i@earthlink.net