[rollei_list] Re: 6 x 9 search
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Thu, 30 Aug 2007 17:53:25 -0700
----- Original Message -----
From: <qwhozeiss@xxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Thursday, August 30, 2007 4:25 PM
Subject: [rollei_list] Re: 6 x 9 search
Wrong----on a Speed of Crown Graphic with the Kalart
rangefindger you can focus more than one len. You need
not go to the ground glass to handel longer or shorter
lenses. You find were the infinity is on said len is and
lock it down with another set of Graphic infinity blocks.
Then use the rangefindger as normal. The rangefindger is
stupid, it doesn't know what lens is on the camera, all it
knows is were 10-15-25-50 etc. feet are, it's an optical
ruler. Sometime people want to make takeing harder then
it is.
T. Mike
That won't work. While the infinity stop will get the
alternative lens set at infinity no other distance will be
right. The extension of each lens from infinity will be
different. The rangefinder will simply move the focus track
to the position it would be in for the lens its calibrated
for. If, for instance, the RF is calibrated for a 150mm lens
and a 127mm lens is mounted and set at a second infinity
stop the RF will want to move the front quite a bit too far
to focus on closer distances.
The only way to focus alternative lenses without using
the ground glass is to mount auxilliary distance scales on
the bed along with a set of infinity stops for each lens.
The scale is set up for each lens. To focus use the
rangefinder and read the distance from the scale for the
"normal" lens and transfer it to the focus scale for the
lens in use. That will get you very close.
For Speed and Crown Graphics Graflex supplied a great
many scales. These were for several nominal focal lengths
and for a range of typical variation of production lenses
for that focal length. Scales are getting hard to come by
now so getting an exact match may be difficult unless you
make your own. The matched scales are very close and usable
for tape measure focusing. If you have only an approximate
scale it is useful mostly for adjusting flash exposure.
BTW, I have never seen anything in print about how
Graphic focus scales are calibrated. The theoretically
correct point is the entrance pupil of the lens but many
cameras have focus scales calibrated from the focal plane.
The latter is useless for determining bellows extension
exposure correction for very close distances. However, the
Graphic scales go down only to about 4 feet.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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