Footwear Impression Photography
Robert E. Kramer; Detective
Cedar Falls Police Department - 220 Clay Street - Cedar Falls, IA
50613
(319) 268-5132
cfpdlab@mchsi.com
Introduction:
The purpose of this article is to
discuss the process of recording footwear impressions on film.
Steps and considerations presented will be done so systematically
in order to provide you, the reader a "checklist" to
study in order to prepare you for this most important evidence
recovery exercise.
Definition:
The term "impression" will
be used a number of times in these exercises. For the purpose of
our discussions, impression/s will be defined as both two and
three dimensional images of footwear which are found at a crime
scene. For example: a two dimensional image would be that of a
dusty footwear image found on a piece of glass in a door at the
point of forced entry to a burglary. A three dimensional image
would be a footwear impression recovered in snow.
Necessary Equipment:
A good quality 35mm or 120mm
camera should be the focal point of any crime scene examiner's
camera bag. The camera should have adjustable f/stops (aperture
settings) and adjustable shutter speeds. A standard lens would be
the lens of choice for footwear photography, as a wide angle lens
would tend to distort the image being recorded. Even though many
footwear impressions may be photographed in daylight, a flash
attachment should be mandatory. Make sure the flash has a feature
allowing it to be held "off camera", as using a flash
attachment in footwear photography is always done in this manner.
(This will be discussed more later.) A remote shutter cord and
tripod should also be considered as standard equipment, as
footwear photography is sometimes done in low light situations
requiring slow shutter speeds. Remember ... a good rule of thumb
is to never attempt to hand-hold a camera at a shutter speed
slower than 1/30th second. Finally: remember to always have a
scale available and in every footwear photo you take, and the
reason is obvious:
The purpose of taking a photograph of
a footprint is to record it for possible future comparison/s with
a suspect shoe. In order for the darkroom technician to make a
scale enlargement from the negative you provide, a scale - or
ruler - will have to be in the image next to the impression. The
scale preferred by me is a 6" plastic ruler in an 18% gray
color. These are available from any crime scene product supply
company. If you know of no such company, contact me and I'll give
you several company names.
Recording the Impression on Film
The two dimensional print often is
the most difficult to recover and document through photography.
Imagine the dusty print on the door as referred to previously in
the "definition" section. Every one of us has probably
seen one of these prints. The first step to consider in taking a
photograph of such an impression is to take it from the same side
on which the impression was made. Yes - you would be surprised -
I have gotten photographs turned in to me of impressions which
after examination I discovered were "backwards." Three
dimensional prints offer their own difficulty factors, but many
of the same techniques are used as with the two dimensional
print. In preparing to take the photo, I encourage you to step
back a bit, take a break, and assess the situation. Remember,
this may be the only chance you get to photograph what may be a
most important part of the on-scene investigation. First of all,
check the lighting surrounding the scene. If you are outdoors,
and it's sunny, a three dimensional print in a soft medium such
as sand or snow may be rather easy. By the same token, daylight
coming through the glass on which the now dusty print is found
can also be an benefit. Let's examine the latter print first.
The first thing to consider
(and this goes for three dimensional prints as well) is to fill
the frame in the viewfinder of the camera with the print. In
other words, if you are six feet tall, don't take the photo from
a position at what your normal eye level would be. Bend over! Get
as close to the impression with the camera as possible! The
primary reason for doing this is that the darkroom technician
will not have to enlarge the negative so much that the print
would lose definition. Next, affix a scale to the glass next to
the impression. In an example such as this you could use
"ruler tape" which quite simply is tape on a role with
ruler markings printed right on the tape. Next, load the camera
with black and white or color film, preferably a film with an
ASA/ISO of no faster than 100. If the print is on a glass with
daylight coming through the glass from the backside of the print,
this will be a very easy print to photograph. By
"bracketing" the exposure (allowing for a degree of
over and under exposure) the photograph can be taken with
relative ease. Here's a tip that I learned early on as I began
photographing prints in these situations. If possible: have a
partner stand back (and behind) the print on the glass as s/he
casts a shadow on the print itself. The best means of doing this
would be to actually hold a large dark cloth behind the print yet
far enough away from it to still allow the daylight to strike the
image on the glass. The idea of the technique is to (while still
allowing the sunlight to illuminate the image) give a dark and
even background in the photo which permits a non-cluttered look
to the photo.
If the print is on glass
indoors, or under lighting conditions so dark as to necessitate
the use of a flash, adaptations of the technique are necessary,
and if mastered, exceptional photographs will be realized. The
biggest enemy to the photographer in a situation such as this is
the reflection of the flash "bouncing" back from the
reflective glass surface into the camera lens. The flash
"burns" the negative, causing flashspots on the film
which are then reproduced in the print. To overcome this problem,
attach your flash to the camera with the aid of a coil cord and
hold it (the flash) at an angle of between twenty and forty
degrees from the plain of the glass surface:
When the flash goes off, it will skim across the reflective
glass, illuminate the print, and not be reflected into the camera
lens. Following your photography, the two dimensional print may
in fact be "processed" with an instrument such as a
Static Dustprint Lifter." This valuable piece of law
enforcement equipment actually "lifts" dust and dirt
from a surface by means of recording film and electro-static
charge. The technique used will not be discussed in this article,
but you should become familiar with such a piece of equipment as
you get more serious in your crime scene work.
Three dimensional prints may
not have the reflective surface causing a problem as a two
dimensional print would, but a print in a soft medium has it's
own difficulty factor, and that is: depth. The same equipment is
used to photo these prints as the two dimensional print. What
makes these impressions different is the manner in which the
tread design on the surface of the sole and heel of the footwear
is captured. This is done easily outdoors in existing light
situations when the sunlight itself is causing a shadow effect
across the print:
In a case such as this, merely adding a scale to the scene and
taking an accurate meter reading of the existing light, an
acceptable photograph will probably be obtained. (More on
positioning the scale later.) When the print is itself in shadow,
the need for an electronic flash to "cause" the shadow
effect is necessary. As with the two dimensional print, position
the flash off camera at an angle from the surface of the print.
If the flash is so equipped, "test fire" the flash
while you observe the print from directly above and in a position
where the camera will be placed. In doing this, you may get a
very good indication as to what angle the flash should be placed,
and from what direction it should be originating from.
Tip ... when photographing the three dimensional print, be
careful to not hold the flash too close to the ground level (at
too shallow of an angle.) The result of doing this would be that
the flash (light) would skim across the top of the impression at
such a shallow angle it would cause the impressed print to show
up as a shadow in the photo.
It is extremely important to place
the scale (ruler) on the same plain as the base of the impression
when photographing a three dimensional impression In other words
... if you are going to photograph a footwear impression found
with the base one inch deep in sand, you must dig a one inch deep
furrow next to the impression and place the ruler in the furrow.
This is necessary in order that when making the scale
enlargement, the darkroom technician will be able to obtain an
accurate reproduction of the footwear impression found at the
scene.
Summation
You wouldn't wait until the night of
a multi-thousand dollar loss safe burglary to learn how to
recover fingerprints with the aid of black powder and a brush,
would you? For the same reason, practice is the key word in
preparation for footwear impression photography. Get out there
now and practice. Make a number of both two and three dimensional
footwear impressions. Practice photographing them using existing
light and an electronic flash. Don't let this procedure
intimidate you. By practicing sound procedures, footwear
impression photography will be a rewarding and a successful part
of your on-scene and laboratory examinations.
Check List
A camera with adjustable f/stops (aperture settings)
and shutter speeds.
Electronic flash with coil cord for "off-camera" flash
work.
Tripod and remote cable release.
A scale.
Fill the frame. Position the camera directly above the print.
If photographing a transparent surface, try to make the
background "uncluttered."
Use a flash if necessary, but never directly "into"
glass.
Not too shallow of an angle in three dimensional photography.