You might want to check http://www.tpwd.state.tx.us/news/news/990913c.htm
Texas Parks and Wildlife had the Hueco Tanks rock art photographed in a similar manner.
Barbara Hickman, TxDOT


>>> geoff carver <[log in to unmask]> 05/19/2000 2:49:00 PM >>>
[log in to unmask] schrieb:
> Some interesting information about the photographic techniques used by Jim
> Henderson of Oregon City, Oregon to bring out faint and virtually invisible
> (to the human eye) inscriptions on historic rock art along the Oregon Trail
> can be found in the Northwest OCTA website at:
>
> http://nwocta.com/newsletters/99jul/kelton.html 
>
> He is currently carrying out work for the Park Service at City of the Rocks
> in Idaho.  His technique, using polarized lighting and computer enhancement
> to bring out inscriptions on historic rock inscriptions, has wide ranging
> possibilities for both historic and prehistoric rock art panels, especially
> where it's difficult to discern images.
>

bit more reliable than barry fell?

geoff carver
http://home.t-online.de/home/gcarver/ 
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