FORS211

FORENSIC PHOTOGRAPHY

LESSON 3
 LIGHT

◼ is one of number of known form of radiant

electromagnetic energy which travel in wave motion.
Actually, there are other theories that explains the
behavior of light but for one purpose, the wave theory
is the only one considered. This form of energy travels
at speed of about 186,000 miles per second in air,
but they differ in wavelength and frequency.
 WAVELENGHT
Wavelength is the
distance from crest (highest
point) to the wave of the next
succeeding crest.

FREQUENCY
Frequency is the number
of waves passing in a given
point in one second.
 THEORIES OF LIGHT
1. Wavelength Theory (James Maxwell)

❖ The wavelength of light is the most pertinent, particularly in

the design of lenses. It is best illustrated by dropping of a
stone in a pond of still water.

❖ The series of wave which travels outward from the center

point are just like light waves that travels in all direction from
a source with equal velocity.

❖ The theory maybe used to illustrate reflection, interference,

refraction, diffraction and polarization.

2. Quantum Theory
❖ In 1900 Max Plank theorized that light might be made up of little bundles
of energy named Quanta.
❖ A quantum of light is called photon. When a photon strikes a light
sensitive surface, it gives energy of electrons within a metal explain the
photoelectric current.
❖ It is used to explain X-radiation and photo electricity.
 FOUR PHOTOGRAPHIC RAYS
2. Ultra-violet rays – radiation
1. X-ray – radiation having a having a wavelength from 30 to
wavelength between 01 to 30 400 milli-microns. It is used to
nanometer or milli-microns. They are photograph fingerprints on
produced by passing an electric multi-colored background,
current through a special type of documents that are altered
vacuum tube chemically or over writings and
detection of secret writings.

4. Infra-red rays - radiation having

a wavelength of 700 to 1000
3. Visible light rays or White
milli-microns. It is used in taking
light – rays having a wavelength
photographs of obliterated writing,
of 400 to 700 milli-microns
burnt or dirty documents or blackout
photography.
FOUR PHOTOGRAPHIC RAYS
 EFFECTS OF LIGHT WHEN IT HITS AN OBJECT

◼ When a light wave hits an object, what happens to it

depends on the energy of the light wave, the natural
frequency at which electrons vibrate in the material and
the strength with which the atoms in the material hold on
to their electrons. Based on these three factors, four
different things can happen when light hits an object:

● The waves can be reflected or scattered off the object.

● The waves can be absorbed by the object.
● The waves can be refracted through the object.
● The waves can pass through the object with no effect.
 GENERAL TYPES OF LIGHT
1. Visible Light
Light with a wavelength of 400-700 nm

2. Invisible Light
Lights with shorter of longer wavelength
 Visible light waves are the only
electromagnetic waves we can see. We
see these waves as the colors of the
rainbow. Each color has a different
wavelength. Red has the longest
wavelength and violet has the shortest
wavelength. When all the waves are seen
together, they make white light.

When white light shines through a prism or

through water vapor like this rainbow, the
white light is broken apart into the colors of
the visible light spectrum.

What’s the difference between visible light and invisible light? It’s all in your head—specifically, in your eyes.
Whether a particular wavelength of light is visible or invisible depends solely on which wavelengths your eyes
can detect. If your eyes were tuned to different wavelengths, new wavelengths of light could become
visible—and some colors you can see now might become invisible.
 WHITE LIGHT

When all the wavelengths between 400-700 nm are presented to the eye in nearly
equal quantity, we get the sensation or perception of colorless or white light.
If a narrow beam of white light is allowed to pass a prism it will bend the light of a
shorter wavelength more than those with longer wavelength thus speeding them out
into the visible spectrum. These are the colors of the rainbow.

Note: White light is the sum total of all colors of the rainbow while
Black is the absence of all colors.
If we will divide the wavelength of visible light into three, we will produce:
● Blue
● Green
● Red
PRIMARY AND SECONDARY COLORS OF LIGHT
WHAT ARE KINDS OF OBJECT AS TO HOW THEY BEHAVE TO LIGHT?

1. Transparent Object
Allows sufficient visible light to pass through them that the
object on the other side may be clearly seen.

2. Translucent Object
Allows light to pass, however diffuse it sufficiently that
objects on the other side may not be clearly distinguished.

3. Opaque Object
So greatly diffuse the light that recognizing the object on
the other side is very difficult if not impossible.
WHAT ARE KINDS OF OBJECT AS TO HOW THEY BEHAVE TO LIGHT?
PROPERTIES OF LIGHT
1. Reflection
- It is the deflection or bouncing back of light when it hits a
surface.
Regular
- Happens when light hits a flat, smooth and shiny surface.

Irregular of diffused
- Occurs when light hits a rough or uneven but glossy object.

2. Refraction
The bending of light when passing
from one medium to another.

3. Diffraction
The bending of light when it hits a
sharp edge opaque object.
4. Rectilinear
- The nature of light that normally travels in
straight line.

5. Interference
- Color can be produce by interference of
lightwaves in thin film like in soap bubbles or a film of oil
floating in water.
- The light reflected from the top surface of such a
film undergoes a reversal or phase but light reflected
from the bottom of the surface does not undergo this
type of change.

6. Absorption
The nature of light to be absorbed in the process of dark
surface.
 7. Filtration
The character of light to be altered from its colorless
into visible state.

8. Polarization
The process by which the vibration of light are
confined to a definite plane, and the speed of light
can be measured.

9. Fluorescence
These happen when molecules of the fluorescent material
absorb energy at one wavelength and radiate it at another
wavelength.
 WHAT ARE SOURCES OF LIGHT?

1. Natural
Coming from nature like the sun, moon, stars, other heavenly bodies, lightning, etc….
The intensity of the sunlight falling on open space varies depending on the weather
condition, time of the day, or even time of the year.
For more accurate exposure in daylight, only one characteristic is considered – the
kind of shadow casted by an object in open space.

a. Bright Sunlight
A lighting condition where objects in open space cast a deep and uniform or
distinct shadow.

b. Hazy Sunlight
Objects in open space cast a transparent shadow.
 WHAT ARE SOURCES OF LIGHT?

c. Dull Sunlight
- Objects in open space cast no shadow.

❖ Cloudy Bright
- Objects in an open space cast no shadow but objects at far
distance are clearly visible.

❖ Cloudy dull
- Objects in an open space cast no shadow and visibility of
distant objects are already limited.
 WHAT ARE SOURCES OF LIGHT?

2. Artificial
- Light sources of this category are man-made and are divided into the
continuous radiation and short duration.

a. Continuous Radiation
- Those that can give continuous illumination.

b. Short Illumination (flash unit)

- It gives a brief flash of light produced by a burning metallic wire (flash
bulb) or an electrical discharge through a gas-filled tube (electronic flash).
 WHAT ARE FORENSIC LIGHT SOURCES

1. Ultra violet lamp

- It comes in a variety of shapes, sizes and
power.
- Some units are portable battery operated and
are easily carried and can meet the rugged and
rigorous demand for field work.

2. Laser – Light amplification through stimulated

emission of radiation
- By illumination certain items with LASER, they
would fluoresce or could be made to stand out in
sharp contrast with their background.
- This was especially significant in locating dried
biological stains.
 WHAT ARE FORENSIC LIGHT SOURCES

3. Alternative Light Source (ASL)

- Far more inexpensive alternative to
Forensic Laser.
- It uses a variety of band pass filters to
provide a high intensity beam of a
non-coherent light.

4. Forensic Light Sources (FLS)

- Applied to a wide variety of relatively
inexpensive light sources which use filtered
white light.
 CAMERA AND ITS ACCESSORIES

◼ A camera is basically nothing more than a light tight box

with a pinhole or a lens, shutter at one end and a holder of
sensitized material at the other. While there are various
kinds of camera from the simplest construction (Box-type)
to the most complicated, all operate on the same
principles. The exposure of the sensitized material to light
is controlled by the lens and its aperture, and the shutter
through its speed in opening and closing the lens to light.
 EARLY FORMS OF CAMERA
1. Pinhole Camera
– a camera of simple design and
construction usually home-made
consisting of a box having a small
aperture functioning as lens at one end,
the image being projected on the film at
the other end.

FOCUSING SYSTEM FOR PINHOLE / A PINHOLE PHOTOGRAPH

2. Box Camera
– a simple camera is little more than
a pinhole camera. It has a lens and
shutter. In the box camera, the pinhole is
replaced by the lens to enable the
photographer gather more light to be
recorded.
 EARLY FORMS OF CAMERA

3. Camera obscura
- (Lat. dark chamber)
was an optical device
used in drawing, and one
of the ancestral threads
leading to the invention of
photography.
 MAIN KINDS OF CAMERA
1. Box Camera
2. View Camera
The biggest and the most sophisticated among
the different types of camera.
A version of press cameras; they have removable
lenses, can be focused by moving either the front
or the rear of the camera, and are equipped with
long bellows.
The back can be moved or swung both vertical
and horizontal axes and its lens board raised,
lowered or tipped.
This flexibility enables the photographer to control
the image formed by the lens.
Practically useless for Candid or action
photography.
Useful and effective in the reproduction of small
objects.
2. Reflex Camera

a. Single Lens Reflex (SLR) Camera

- The term “Single lens” means that only one is
used for both viewing the scene and taking
photographs of it, thereby preventing parallax. It has
a detachable lens and is mostly used in police
photography.

Parallax
● The difference between what is seen through the
viewfinder and what is exactly recorded on the
film.

b. Twin Lens Reflex Camera

Employs 2 separate lenses – one for viewing and
one for focusing, and the second is usually
mounted under the first, transmitting the light to
the focal plane recording.
The camera has permanently fixed lenses and
an automatic parallax adjustment.
Its two lenses focus in unison so that the top
screen shows the image sharpness and framing
as recorded on the film in the lower section.
3. Polaroid Still
- This camera is restricted in its uses but ideal in
instant photograph when there is no requirement for
enlargements.

4. Digital Camera- A digital camera (or digicam)

- is a camera that encodes digital images and
videos digitally and stores them for later reproduction.
Most cameras sold today are digital,[ and digital
cameras are incorporated into many devices ranging
from PDAs and mobile phones (called camera phones)
to vehicles.
ESSENTIAL PARTS OF A CAMERA

1. Body or Light Tight Box

– suggest an enclosure devoid or light. An
enclosure, which would prevent light from
exposing the sensitized material inside the
camera. This does not necessarily mean that the
box or enclosure to always light tight at all the
time because if it does, then no light could reach
the sensitized material during exposure. It
means that before and after the extraneous light,
which is not necessary to form the final images.
2. Lens
– the function of the lens is to focus the
light coming from the subject. It is chiefly
responsible for the sharpness of the image
formed through which light passes during the
exposure.

3. Shutter
– is used to allow light to enter through
the lens and reach the film for a
pre-determined interval of time, which light is
again blocked off from the film.
ESSENTIAL PARTS OF A CAMERA

4. Holder of sensitized material

– located at the opposite side of the
lens. Its function is to hold firmly the
sensitized material in its placed during
exposure to prevent the formation of a
multiple or blurred image of the subject.

5. View-finder
– it is a means of determining the field
of view of the camera or the extent of the
coverage of the lens.
WHAT IS THE FIRST DIGITAL CAMERA?

1975 Kodak digital camera prototype

Created in 1975 by Steve Sasson,

an engineer at Kodak, the first ever
digital camera was a fairly
rudimentary affair compared to
what we use today.

1994 Apple QuickTake 100

The first digital cameras for the

consumer-level market that worked
with a home computer via a serial
cable were the Apple Quick Take
100 camera.
WHAT ARE OTHER TYPES OF CAMERA? (ACCORDING TO FILM USE/S)

1. Press Camera
A camera loaded with a sheet of
film.
They are traditional folding
bellows designs with a lens
standard in an extendable
baseboard.

2. Underwater Camera
Designed for underwater
photography.
 WHAT ARE OTHER TYPES OF CAMERA? (ACCORDING TO FILM USE/S)

3. Wide View angle Camera

A camera with a wide angle
lens that produces a
rectangular image that is
designed for landscape
photography and architectural
photography.

4. Panoramic Camera
Used for landscaping
photography.
It is easy to use by
encompassing a 120®, 180®,
or 360® view of one
exposure.
WHAT ARE OTHER TYPES OF CAMERA? (ACCORDING TO FILM USE/S)

5. Still Video Camera

Images can be stored
in video tapes
equipment with a
floppy disc, a disc that
can hold about 50
images or more.