28 Mar
2018
28 Mar
'18
4:19 p.m.
On Mar 28, 2018, at 1:35 PM, Fred Cisin via cctalk
<cctalk at classiccmp.org> wrote:
On Wed, 28 Mar 2018, Ethan via cctalk wrote:
This is the part I?m having trouble wrapping my brain around, but then I?ve not messed
with that many fiche readers. I?m far more familiar with film holders. Too bad it isn?t
a question a running 35mm film through, as Beseler Negatrans would work for that.
If you can take a fiche reader, and modify the fiche holder mechanism to handle this, then
you?d be most of the way to doing this manually. Realistically a manual setup with a
shutter release cable would still let you fly through the fiche pretty fast.
We are like engineers or something. I think there
is open source software for rebuilding images from shredded documents.Slide projector
lens, LED array and diffuser and a digital camera. Stepper motors to move the thing around
and load next fiche?
Let the robot do it?
In other words, a homemade fiche scanner.
If you start with a fiche viewer, then a lot of the mechanical parts, such as the fiche
holder, are well under way. You need to modify the card movement mechanism to be able to
automate it, but you could put that part off until you confirm that the optical portion is
satisfactory. Added extension shortens the distance from lens to
subject. An added extension equivalent to the focal length of the lens will change the
focus from infinity down to twice the focal length from the lens, which will give you
one-to-one. In other words, adding 2 inches of extension to a 50mm lens will bring the
focus to 4 inches from the lens. You want a fair amount more than that.
I think Bellows would be the only sane way to approach this. You could do it with
extension tubes, but they?re a pain. Another thing to consider is a light source. You?re
going to need a fair amount of light, given the necessary extension to get the
magnification.
If you want help with the formulas for extension, just
ask.
My favorite source for that kind of information is a 1936 edition of "The Leica
Manual" by Morgan & Lester.
One of my favorite books, I think I?m up to 5 editions of it. :-) You?d be hard pressed
to find a photography book with more data in it!
Zane