[Ohiodig] Fwd: Scanning Transparent Documents

[Noah Stegman Rechtin]

Dear All,

Could anyone offer any suggestions on how to best scan partially
transparent documents? I know this sounds like a joke, but it's a serious
question.

Yesterday, an individual donated a number of World War II manuals to our
museum and one of them, a description of the C-1 autopilot vertical flight
gyroscope, uses what was at the time a brand new technology called
"Trans-Vision". (It was apparently originally popular for medical
instruction, so another name for the format seems to be "anatomical
transparency <http://onlinelibrary.wiley.com/doi/10.1002/ca.21028>".) The
document has a sequence of transparent pages that incrementally show more
layers of the device as each page is turned. For example, the exterior of
the case, a pair of guides for the rotors, the rotor case, the rotor itself
and finally the motor inside.

The difficulty is that the transparency is a key point of how the
manual functions. Each page, to a greater or lesser extent, relies on the
illustration on the next one, as it only shows a portion of the
whole device. Furthermore, each page is double sided, so that the front and
back side of each layer is shown on the obverse and reverse of each page.

I'm guessing that the best way to handle it is to just scan all of the
pages together and try to capture the details on the page behind it
together as one page. The alternative would be to try to scan each page
separately. In theory, with the correct implementation and adjustments,
this would be the more accurate depiction. However, it would require keying
out the background with an alpha layer
<http://en.wikipedia.org/wiki/Alpha_compositing> *and* a book viewer with
the ability to display the underlying page in addition to the one (or,
rather, two) that is usually visible.

Sincerely,
Noah Stegman Rechtin
*Collections Manager & Museum Attendant*
*Tri-State Warbird Museum <http://www.tri-statewarbirdmuseum.org/>*
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