used when recording petrogyphs on Ometepe Island
can be maddeningly difficult to photograph. They are almost
always located in a remote area. Trudging to them with the
100 pounds or so of equipment that might be required to light
and photograph them properly is generally inadvisable, especially
in the tropics in summer. In any case, one usually arrives
at a time of day when the "natural" light, so poetically
described and utilized by Ansel Adams, is more of a hindrance
than help. The engraved or pecked lines may be so shallow
as to be almost invisible. Erosion can make any petroglyph
faint enough to be missed by the casual observer. So what's
an archaeologist with a bad back, arriving at an inopportune
moment with rudimentary equipment and many petroglyphs to
record, gonna do?
little background is in order. On Ometepe Island, the depth
of the engraved lines on recorded petroglyphs varies from
immeasurably shallow to around three centimeters. As an example
for our discussion on how to photograph difficult situations,
let's use the petroglyph R29-P1 from N-RIO-3, the one that's
used as the background for the Field Notes page.
petroglyph is found on a nearly vertical slab of basalt bedrock.
The panel measures 210cm high by 300 cm wide. Another slab
of basalt immediately adjacent and at a right angle to R29
contains another human figure similar to the 5 found in R29.
Together they form what may be described as a family, if archaeologists
were allowed to make wild and unwarranted judgments.
the finished photo. In this case we were unable to block
the background light completely, so there are some
deep shadows on the face of the petroglyph.
the reflector brought out details that even the sketcher
hadn't seen before.
first step taken in recording and petroglyph was to draw the
entire panel and fill in a petroglyph form. On petroglyphs
as faint as this one, the drawing was often done by a sort
of Braille technique, with the recorder tracing nearly invisible
grooves with the tip of her fingers. Once this task was completed,
the photographer, namely me, would saunter over and take a
photo using the following technique.
the direction of the light is determined, then a small, portable
reflector is set up to cast light at an oblique angle over
the petroglyph surface. If warranted, the direct sunlight
striking the petroglyph surface is blocked by tarp, so only
the reflected light remains. This often brings out enough
luminance variation over the rock surface that the sketcher
will see even more detail that even a close examination by
sight and touch had previously missed. Changing the angle
of the reflector only slightly often brings out additional
detail. Several photographic exposures are made, often with
slight variations of reflector angle.
here's the basic setup. A portable reflector is used
to reflect available light so that the grooves in the
petroglyph are in deep shadow.
however, does a petroglyph appear on the porch of a
19th century hacienda. But that's the problem
in Nicaragua and around the world these days, the smaller
finds are quite often carted off for souvenirs.
at home, the black and white film is developed to add about
one paper grade of contrast by increasing development time
by about 20%. Then the photographs are scanned into Photoshop.
Here the contrast can be enhanced, the shadows cast in the
grooves can be deepened and the parallax error that occurs
when the camera lens cannot be brought completely parallel
with the rock face can be corrected using data extracted from
the rock face has a curvature that makes it difficult to light,
separate exposures can be taken with the light corrected for
different areas of the petroglyph face and the photographs
layered in Photoshop. Then each layer can be combined in a
way that utilizes the best lit areas from each layer to produce
a final file for printing.
reflector shown in these pages is a Litedisc
produced by Photoflex.
It expands to 32" and folds for storage and transport
to about 12" in diameter. It's a bit tricky to fold up,
but once you get the hang of it the whole process looks like
magic. And folding the reflector for storage was a source
of endless fascination for the local kids!
reflectors can be purchased with different coatings on each
side. Ours is silver on one side for reflection and black
on the other to hold light back from an object.