Among experts on conserving old funeral monuments, particularly in New
England, rubbings have a very bad reputation due to the extensive damage
that has been done to fragile marble gravestones.

Applying any sort of chemical (except water) to the stone is also very
much frowned on.

Quite relevant to the discussion here are this and the following message
(recently posted on GRAVE-L, the historic cemetery mailing list) from
Chris Breyer, a photographer, about the use of oblique flash to bring out
subtle details in deteriorated grave monuments.

Forwarded to BP with permission.

---
Lawrence Kestenbaum, [log in to unmask]
The Political Graveyard, http://politicalgraveyard.com


---------- Forwarded message ----------
Date: Tue, 07 Sep 1999 14:01:51 -0700
From: chris breyer <[log in to unmask]>
Reply-To: [log in to unmask]
To: [log in to unmask]
Subject: oblique flash photography (as applied to headstone markers)


i did not expect to arouse such interest in photographic methods of
headstone marker inscriptions.  i'm more than happy to provide the
following info.  please excuse any 'lingo' or technical terms which may
not be immediately apparent.  if further explanation is necessary, please
let me know.

getting set up in equipment for oblique flash photography could cost you
some money.  i should think it could easily cost above $100, perhaps as
much as $500.  being only a photographer out of necessity, not as a direct
occupation, i apologize in advance to all photographers who know what the
heck i'm talking about.

you must have a camera (35mm most commonly) which has a 'hot shoe' flash
connector.  i am used to using a thyristor-controlled flash (where the
thyristor is removable) in combination with the camera.  in brief, the
thyristor is a sort of detector on the flash which, when a flash photo is
taken, judges how much light from the flash bounces off of the
photographic subject, and returns to the flash.  this allows the flash to
analyze how much illumination of the subject is being accomplished with
the flash, and simultaneously cuts off the flash power when it judges the
subject to be sufficiently illuminated.  this prevents over-exposure of
the subject being photographed.  since in normal, direct flash
photography, the thyristor is mounted on the front of the flash, with the
flash mounted directly on the 'hot shoe' of the camera, the thyristor is
then directly over the camera lens, and is an effective control of the
illumination of the subject as it passes through the lens of the camera
onto the film.

the above is how the system works in 'normal' direct flash photography.

in oblique (read:  low-angle incidence) flash photography, the above
system must be altered.  the flash must be removable from the camera (hot
shoe), and the thyristor must be removable from the flash.  for this, one
cord should be all that is necessary. i believe this cord is called a
'sync' cord.  The sync cord connects the 'hot shoe' of the camera to the
thyristor position of the removable flash (with the thyristor unit
removed).  The end of the cord which is mounted to the camera's hotshoe
will have a receiver to plug the thyristor into.

this setup allows the the thyristor to properly control the amount of
light entering the lens of the camera regardless of how or where the flash
is held, assuring the best exposure of your photograph.

*whew* ok, now for the ACTUAL technique of oblique flash photography.

you can set up a tripod if you wish, for the camera.  this will probably
make the whole task much easier.  as a matter of personal preference, i
usually work without tripod, as in my line of work all sorts of limber
contortions may be necessary for getting the best shot.

set up your camera so that it is looking directly at the object to be
photographed.  in your case, this is the headstone marker.  set up your
composition for the desired effect (i.e., frame fill, background, etc.).
once you have this all set and focussed, you want to have the flash (on
sync cord) positioned off to one side of the headstone marker, out of the
field of view.  angle the flash so that the light will hit the marker, and
then bounce away in the opposite direction at a similar angle, as if it
where a ray of light.  take the photograph.  some of the light hitting the
headstone will bounce into the lens of the camera, creating your negative
image on your film. The thyristor mounted on the camera hotshoe will make
sure that enough light reaches the film to create a good image.

this oblique flash technique maximizes contrast in your headstone image by
shadowing depressions, and lighting the flat areas.

i highly recommend practice with a roll of film at your local graveyard
before you go for your critical shots of 400 year old markers.  it may pay
off for you to take two exposures of each marker, with the flash held at
an oblique angle on one side of the marker in the first, and a similar
oblique angle from the other side of the marker in the second.

in my profession (forensics), i commonly use this technique to record a
number of different impressions (usually footprints or tire imprints in
soil at a crime scene). with practice, this technique can photographically
record shoe imprints in dust on a shiny, smooth floor.  your results will
probably vary, but practice, practice, practice is the key.

accomplished photographers with a hand-held light meter can probably
accomplish this technique without a thyristor.  i recommend a thyristor
for the rest of us.

i only have experience with the "Vivitar 283" flash.  it is not a
dedicated flash, and can be adapted to practically any camera which has a
hotshoe.  i cannot recommend it over any other flash, as it is the only
flash i have used in this manner.  i believe it can be had for less than
$200.

i apologize for being so long-winded.  this really isn't as hard as it
sounds.

if you want to see oblique lighting in action, go outdoors at night
wearing athletic shoes with a distinctive tread pattern.  bring a flash
light.  step into different types of dirt, and then use the flash light to
observe your imprints.  observe which angle you must hold the flashlight
at to best observe the the pattern in the imprint. this in effect is what
oblique flash does for you.  i happen to think it will give you results
far superior to standard photography or 'rubbing' techniques.

best of luck!

chris breyer