<div dir="ltr"><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Dear All,<br></div><div dir="ltr"><div dir="auto"><div dir="ltr"><div><br></div><div>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.</div><div><br></div><div>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 "<a href="http://onlinelibrary.wiley.com/doi/10.1002/ca.21028" rel="noreferrer" target="_blank">anatomical transparency</a>".) 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.</div><div><br></div><div>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.</div><div><br></div><div>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 <a href="http://en.wikipedia.org/wiki/Alpha_compositing" rel="noreferrer" target="_blank">alpha layer</a> <i>and</i> a book viewer with the ability to display the underlying page in addition to the one (or, rather, two) that is usually visible.</div><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div style="color:rgb(34,34,34)">Sincerely,<br></div><div style="color:rgb(34,34,34)"><div>Noah Stegman Rechtin</div><div><i>Collections Manager & Museum Attendant</i> <br></div><div><i><a href="http://www.tri-statewarbirdmuseum.org/" rel="noreferrer noreferrer" style="color:rgb(17,85,204)" target="_blank">Tri-State Warbird Museum</a></i></div></div></div></div></div></div></div>
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