Transcript Archaeological photography Practices and Principles

Archaeological Photography
Workshop
Field Archaeology
ARCH1003
Archaeological Photography
Objectives
Photo Documentation (Hester 1997)
A comprehensive and technical record of an investigation from
beginning to end
Excavation, process of recovering artefacts, sequences, units and
profiles, survey finds. It is a historical record
Ethical responsibility of archaeologist to visually record an
irreversible process such as excavation or survey. Subsequent
analysis or re-analysis of your work in future
Photo Illustration (Hester 1997)
To provide images for publication or presentation
What are you trying to communicate to the public or in the journal?
Why photograph and illustrate?
Single Lens Reflex (SLR)
Camera Features
Lens
Lens aperture
Focusing ring
Auto Advance
Aperture or AV value
Hot shoe
Shutter speed or TV
(Time Value)
ISO setting
Shutter release
Frame counter
Focal plane shutter
Remote release
socket
Film Window
Mirror
Prism
Light
Light is focussed through a lens by refraction
(bending of light rays) to form an image
behind the lens
To produce a photograph we need:
A light source
An object such as a mirror to reflect the light
A light sensitive medium to record the
reflected light (film/digital sensor)
Colour temperature (degrees Kelvin)
Aperture Value
Aperture = f/stop = AV (Pentax camera)
Size of the aperture opening in the lens
A large number (F22) is a small aperture
A small number (F2.8) is a large aperture
To stop down is to reduce the aperture
The f number derives from dividing the
focal length (mm) of the lens by the
diameter of the aperture
Relationship Between Aperture and
Light
Time Value/Shutter Speed
Time Value = shutter speed = TV (Pentax
camera)
Length of time the camera shutter opens to
expose the film/sensor to the light coming
through the lens
1/8 second or slow shutter speed (requires
tripod to avoid camera shake)
1/4000 or fast shutter speed (captures water
splashing)
Exposure
Exposure is the total amount of light reaching
the film calculated from a combination of
aperture value (AV) and time value (TV)
Reducing the AV value (or f-stop) from f16 to f22
necessitates doubling the exposure time or TV
(time value) for the same exposure result
1/250 second at f22 will give the same exposure
result as 1/125 second at f16 (TV reduced but
aperture opened up)
Depth of Field
Depth of field is the zone extending in front of
and behind the focussed distance within
which points will appear to be sharp
The smaller the aperture (AV 22) increases the
depth of field
The larger the aperture (AV 5.6) decreases the
depth of field
Shorter focal length (wide-angle 28mm)
increases depth of field
Longer focal length (telephoto 300mm)
decreases depth of field
Focal Length
Light travels in parallel beams and reaches the
lens
The distance between the lens and the point at
which such light is focussed is the focal
length of the lens
It is always expressed in millimetres
An object the same distance away from a long
focal lens will give a larger image than one of
short focal length
Standard focal length is 50mm for 35mm
camera (negative is 35mm x 24mm)
Angle of View
The angle of view for the human eye is around
45 degrees
Angle of view is the amount of the scene in
front of camera taken in by the lens.
A fish eye lens (18mm focal length) will provide
180 degrees angle of view
A telephoto lens (1200mm focal length) will
provide 2 degrees
Note: A longer focal length (300mm lens) will
decrease the depth of field
Film speed
ISO film speed is the films sensitivity to light
rating
The more sensitive the film, the higher the ISO
number and the less light required
ISO 6 is a slow, fine grained film and requires a
tripod
800 or 1600 ISO is a fast film (newer films not
so grainy, used with/without flash)
TMax 3200 can be used with available light at
night
Perspective
The apparent distance in the relative sizes of
near and far objects
A function of the distance away of the camera
Wide angle distortion 28 to 35mm may steepen
the perspective of your trench or structure
leading to convergence of lines and
aberrations at edge of negative
Standard focal length lens (50mm) or higher
will give normal perspective
Telephoto lens (above 50mm) may flatten
perspective
Metering
Current Single Lens Reflex (SLRs) cameras
have built in metering
Correct Exposure (Pentax) is when the green
light is half-way and is changed by adjusting
AV/TV values
If positive = overexposed
If negative = underexposed
Note: internal meter reads whole scene not just
object unless that fills the frame
Incident, reflective, spot metering, grey cards
Camera Handling and Care
Dirt, water, dust, sun can damage cameras
and/or precious exposed film
Use bag or waterproof case (e.g. Pelican) for
rainy days
Lens tissue for clearer picture. Check the lens!
filters will help protect the lens
Do not over tighten the tripod screw
Batteries may leak if for a long time in the
camera
Field Equipment
Film! cards/laptop/burner
Batteries
Filters
Special requirements for
digital cameras
Camera hood and
waterproof case
Reflectors
Lens cleaning material
Special lenses
Scale (range pole and/or
centimetre scales)
Additional cameras (black
and white, slide and/or
colour print, digital)
Photographic proforma or
notebook/register
North arrow
Tripod and remote cable
release
Flash/Supplementary
Lighting
General Principles of
Archaeological Photography
Technical Photograph
descriptive and realistic
Control the light
Use an appropriate scale
A scale should be in the same
plane as the object
Viewpoint is critical. Fill the
frame. Use macro
lenses/function for small
objects
Film/CD media is low cost,
while project time is not
Exposure is critical
Record on
proforma/notebook
(Never Later)
Record meaningful
information
A changing landscape?
Detail, Geology,
construction materials,
flora,
Save images to digital
archive at highest
resolution possible and
back up records
Overall Site and Aerial
Photographs
The relationship between a site and surroundings is
essential. Try to convey a sense of context or
environment
Try to take an elevated photograph if possible (wall,
ladder, tree, elevating machinery, box
Conventional aerial photographs - planes,
Low-level aerial photographs - booms, balloons, and
kites
Photo Illustration
Photo Illustration
Aerial Site Overview
Photo: David Webb, UK
Critique Photograph
Critique Photograph
Critique Photograph
Critique Photograph
Scale
Scale Position/Use of Negative
Human Scale/Site Context
Scale/Use of Negative/Cleaning
Direct Sunlight/Contrast
Diffuse Light
Overcast Lighting/Scale/Use of
Negative
Background Placement, Scale,
Glass in Sunlight
Artefact Use Visualization
Finger as Scale
Scale Size/Placement
Scale Placement
IFRAO scale
AURA, PO BOX 216, Caufield
South VIC 3162
[email protected]
Rock Art
IFRAO scale
Studio Lighting
Studio Lighting