Series editors' preface - Wood Tools

fessional quality shots in conservation. More
than anything else the lack of proper background
betrays the amateur effort and interferes
with the main purpose of the record. It is
very useful to incorporate a scale and colour
patch and a ‘slate’ showing object identification,
date and state (before, during and after
conservation).
A one piece background, suitable for larger,
floor standing objects, can be simply made
from a large sheet of plain paper or fabric
unwound from a roll mounted at high level
and gently curving from vertical to horizontal.
The object is placed directly on the background,
well in front to avoid too harsh shadows.
Colour and tone of background should
take into consideration the nature and especially
the colour of the object. Shots taken on
highly coloured backgrounds tend to date
more rapidly and the colour of the background
may lend more of a colour caste to the object
than when black, white or neutral grey is used.
The background should be protected, using
old background paper for example, when positioning
objects on it to avoid footprints and
other marks showing up in the photograph.
The protection should only be removed just
before the photograph is to be taken.
An effective two-piece background suitable
for smaller objects can be formed by placing
the object on a table covered with coloured
paper or cloth at a little distance in front of a
vertical screen of coloured paper. A copy stand
can be used for small three-dimensional
objects. Sets can be lit in various ways. Perhaps
the easiest one is with the camera straight on
and lights coming at an angle from either side
of the camera. Another way is with one light
illuminating background and one at an angle
on the object with the camera at an angle to
the second light.
When even simple background sets are not
feasible it is possible to secure acceptable
results by arranging for the depth of field to be
such that the background is well out of focus.
Alternative light sources
By the selection of appropriate light sources
and equipment, the photographic process can
be extended to reveal elements of both surfaces
and structure not ordinarily visible to the
naked eye. Furthermore, the images obtained
may be subjected to analysis to enable count-
Conservation preliminaries 405
ing or measurement of particular features and
can be digitized in a manner that enables the
image to be manipulated in ways far beyond
those available in the traditional darkroom.
Discrete portions of the electromagnetic
spectrum are subdivided according to their
interaction with atomic and molecular matter.
For example: ultraviolet, visible and infrared
radiation all involve distinct aspects of outer
orbital electrons, X-rays excite inner-shell electrons
and gamma-rays are higher energy emissions
from atomic nuclei. Different energies
within each portion of the spectrum will modify
the results of the imaging processes.
Film or imaging techniques sensitive to these
specific energy domains make it possible to
visualize such characteristic phenomena when
‘illuminated’ by the proper energy source. This
evidence will reveal materials and construction
techniques hitherto concealed from the
unaided eye of the examiner. In general, these
techniques operate on the principle of contrast
between areas of absorption and: reflection
(infrared reflectography), transmission (X-ray
radiography) and emission (ultraviolet illumination).
The five techniques which have the
most widespread application are photography
by reflected UV, photography by reflected IR,
fluorescence excited by UV, fluorescence
excited by IR and X-ray radiography.
When attempting photography by either
reflected UV or reflected IR, the subject must
be lit with lights which emit the wavelengths
by which we wish to photograph. A filter must
then be placed in front of the film (usually over
the camera lens) which passes only those
wavelengths. Electronic flash is a good source
of both UV and IR wavelengths. For UV, an
18A filter is required on the camera and for IR
the filter required is an 87 or 87C. Almost any
black and white film, especially those with
lower film speeds, is suitable for reflected UV.
For reflected IR, Kodak High Speed Infrared
film is recommended.
When some subjects are illuminated by certain
wavelengths they may transform some of
the incident radiation into other, usually longer
wavelengths which are then reflected back
along with the same wavelengths that they
were illuminated by. When a subject behaves
in this way it is said to fluoresce. Some subjects
change short, ultraviolet, wavelengths into
longer visible wavelengths. Others may change