Interesting. I followed some of his links. He doesn't single out the
particular factors I speculated about, but his conclusions about camera
steadiness and vibration damping would deal with them in any case.
Down under the 100lpm section, he refers to 'Kodak Photomicrography
color film #2483'. Back in the early '70s, I conceived of, helped design
and had built a rear projection system for projecting maps and aerial
photos for a major retailer. I used 4x5" transparency film in a custom
built projector. It had a Xenon pressure arc lamp reflected from a
dichroic coated mirror to pass much of the infrared heat before getting
to the film, which had to be air cooled anyway. Condensor lenses from a
4X5 enlarger formed a 'cone of light' ala Beseler. The film carrier
moved up and down in the cone to 3 different positions as a turret spun
1 of 3 lenses into position. All of this was controlled electronically
so the user just put the film into a holder projecting through a slot in
the wall and pressed a button for the desired magnification. There was
also a joystick to move the image around at the higher magnifications.
The screen was 6X7ft., so the base magnification was about 18x. I think
the highest magnification was about 45x. and you could stand right at
the screen to examine the image. Obviously oneof the limiting factors
was film. Looking around, we found a special Kodak film supposedly
originally used for U2s and such. It was real touchy stuff. We built our
own little lab (and quite an interesting custom overhead rail camera,
too!) and learned how to process it in a Merz batch processor. A couple
of times govt. lab people came over to consult with my darkroom guy
'cause their emulsions kept sliding off the backing and down the drain!
After a while they would only make batches of film in 4x5 once or twice
a year, so we'd have to buy a lot and freeze it.
The film did come out later in 35mm and I suspect is the one Monaghen
refers to. It was flat out amazing. Standing next to the screen at full
magnification, there just wasn't any visible grain! And amazing detail
was visible.
We ended up making and installing about 20 of the projectors, serviced
by the one lab. All gone now except some pictures and projection lenses.
We used quality enlarger lenses as projection lenses. Anybody need a
Schneider Componon f5.6 or Rodenstock Omegaron f4.5 in 105, 180 or
240mm? I know I've got some around somewhere.
Moose
Johnny Johnson wrote:
At 04:12 PM 3/24/02 -0800, dreammoose wrote:
It seems to me that vertical motion of a horizontal shutter camera
could cause similar effect on a 35mm SLR. It would be less obvious,
because of the higher relative curtain speed, but might cause
otherwise unexplained 'unsharpness', especially if it were a highish
(technical term) frequency vibration from mirror slap, vertical
diaphram mechanism 'slap', etc. Physical movement from hand held
motion might take the form of barely discernable distortion in
horizontal lines.
Hi DM,
Don't know if you've read the following article or not. While it
doesn't address the questions you've raised it does offer an overview
of some other interesting factors to consider.
http://people.smu.edu/rmonagha/mf/limits.html
Later,
Johnny
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Johnny Johnson
Lilburn, GA
mailto:jjohnso4@xxxxxxxxx
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