Photographing large books

Does anyone have experience with, or equipment or techniques for,
supporting open folio sized books while plates are being photographed?
We are looking for safe ways to support the book at a 90 degree opening
(when possible), with part of the open book supported vertically (like
the vertical part of the letter "L") while the part of the text block
containing the plate to be photographed lies flat.  We've been
experimenting creatively but cautiously, but would like to know how
others have approached and/or solved this problem.  Standard cradle
support isn't always a great choice from the photographic point of view,
because of curvature and angles.  On the other hand (actually, the first
hand) we don't want to do anything to damage the books.  Any information
or ideas anyone can pass along would be appreciated.  Thanks.

Charlotte Tancin
Librarian
Hunt Institute for Botanical Documentation
Carnegie Mellon University, Pittsburgh, PA 15213.

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                  Conservation DistList Instance 6:30
                Distributed: Wednesday, December 2, 1992
                        Message Id: cdl-6-30-005
                                  ***