Archived posting to the Leica Users Group, 2008/05/11

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Subject: [Leica] real focal length of M-Rokkor 2.8/28 and CV 1.9/28 mm ?
From: hoppyman at bigpond.net.au (Geoff Hopkinson)
Date: Sun May 11 16:06:42 2008
References: <8094f2d10805111448o5e5987a3rd2c5b1205e7e43cf@mail.gmail.com>

Jean, it can get confusing with the M8 frame-lines.
For a 28 mm lens you need the 28/90 pair to display. The 28 frames show a
field of view on the M8 that is narrower than on a film M. This is because
the sensor is smaller than 24x36 and so it effectively crops the image. With
a 28mm lens you are getting approximately the field of view of a 37mm lens
on a film M.
If you have a good 28/90 adaptor on your CV it should bring up the 28/90
frames. If it doesn't you might be able to replace it. Not every adaptor on
the market is of equal quality. I have one CV adaptor that brings up the
right frame-lines and one 'no name' brand that does not work properly. You
should ideally have the new style designed for the M8.
Another factor is that the area indicated is approximate anyway and for
longer distances the lens covers more than is shown too.
You might be able to talk to a lens service agent about whether your Rokkor
mount can be adjusted or to John Milich about whether the mount can be
replaced. I would think that your cheapest option would be to just get a new
adaptor from Cameraquest or someone similar and fit it to your CV.
Cheers
Geoff
http://www.pbase.com/hoppyman/e
http://gallery.leica-users.org/v/gh/

-----Original Message-----
Subject: [Leica] real focal length of M-Rokkor 2.8/28 and CV 1.9/28 mm ?

Hi all,

I am glad to be back on this list after a couple of years off!

My recently acquired M8 gave me the occasion to compare the finder
brightlines to the actual field of view.
One of my lenses is a 2.8/28 M-Rokkor (originally for the CLE). On a
M6 it triggers the 35mm framelines, and on a M8 the 35 + 24
framelines.
My other 28mm is the cosina-voigtlander 1.9/28, which I use with a
28/90 adapter ring.

I thought both lenses had the same actual focal length, but in fact
the Minolta-Rokkor is much wider than the CV: on the M8 it corresponds
to the 24 mm framelines.

Does anyone have an idea of which hypothesis is the right one:
(1) the so-called M-Rokkor 28mm is actually a 24 or 25 mm
or
(2) the Rokkor 28 is really a 28, the M8 framelines are wrong and the
CV 1.9/28 is a 32mm or so?

Anyway I am glad that the M-Rokkor mount  triggers the 24 mm
framelines and I did not spend money to get a screw into the mount to
get the 28mm framelines.

Jean

-- 
Jean Louchet
APIS - INRIA Saclay research centre
4 rue Jacques Monod 91893 ORSAY Cedex France
----------------------------------------------------------
jean.louchet@inria.fr http://jean.louchet.free.fr/
----------------------------------------------------------

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Replies: Reply from jean.louchet at gmail.com (Jean Louchet) ([Leica] real focal length of M-Rokkor 2.8/28 and CV 1.9/28 mm ?)
In reply to: Message from jean.louchet at gmail.com (Jean Louchet) ([Leica] real focal length of M-Rokkor 2.8/28 and CV 1.9/28 mm ?)