john10
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Posts posted by john10
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Hi Richard,
The following link may take you to the resolution information you are
looking for.
Best wishes to all for the New Millenium
John
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My lens references show the Trigor lens to be a process lens giving
80 degrees angle of view and it is stated to be of high repute. That
is all I have on this lens.
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My information is that the Dasykar lenses were some of the earliest
Schneider lenses, so were from the 1920's. They were intended for
architectural, interior, and panoramic photography, and also
photogrammetry. They were replced by the Angulons in about 1930.
<p>
They were for 90 to 110 degrees angle of view and were made from 60mm
to 440mm focal lengths.
<p>
The 130mm will cover 7" x 9.5" stopped down. The 180mm will cover 7"
x 9.5" fully open.
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Perhaps you could check if the front and rear elements are inscribed
with their individual focal lengths. It is possible that the single
elements are of 300mm focal length each and the combination of the
two elements is 180mm. This could quite easily be checked out with a
test on the camera.
<p>
Simply focus the complete lens on an infinity subject and measure the
distance from the lens flange to the ground glass and similarly with
the front element removed. If my guess is correct the measured
distances will correspond at 180mm and 300mm respectively. The Ross
combinable lenses worked on this principle, so it is quite possible
that this one does also.
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You could try the following links for starters but also try a Google
search (www.google.com). Type 'pinhole camera' into the search box
and you will get many sources of information.
<p>
http://www.photo.net/photo/pinhole/pinhole.htm
<p>
http://members.home.net/hmpi/Pinhole/Articles/PinholeArticles.htm
<p>
http://amateurphoto.about.com/hobbies/amateurphoto/msub17.htm
<p>
<p>
<p>
http://dir.yahoo.com/Arts/Visual_Arts/Photography/Pinhole_Photography/
<p>
John at JCR Cameras
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As an extension to this question, is there any reasdon to treat
archivally printed digital prints in a different way to conventional
wet printed prints.
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To find the approximate maximum aperture of a lens measure the focal
length of the lens by projecting a sharp infinity image of the
horizon as seen through your room window onto an internal wall and
measure the distance from the centre of the lens to the wall. Then
measure the diameter of the lens in the same units. Divide the focal
length by the diameter to give the maximum aperture. In this case it
would appear to by 45/6 = f7.5.
Resolution Target - Air Force PDF File?
in Large Format
Posted
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<p class="MsoNormal">Sorry folks. My brain is not yet back into gear
after the
Christmas break.</p>
<p class="MsoNormal">The link for a military lens-testing chart is at
the
following link.</p>
<p class="MsoNormal"><a
href="http://www.jmlopt.com/products/targpatt/summary_ch9.html">http:/
/www.jmlopt.com/products/targpatt/summary_ch9.html</a></p>
<p class="MsoNormal">Best wishes,</p>
<p class="MsoNormal">John</p>
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