Police Photography Renz Ventura
Police Photography Renz Ventura
Police Photography Renz Ventura
PHOTOGRAPHY
Renz Ventura
"Photography" from the
Greek words photos ("light")
and graphein ("to draw") The
word was first used by the
scientist Sir John F.W.
Herschel in 1839.
“Photography” is an art or
science which deals with the
reproduction of images through
the action of light, upon sensitized
materials, with the aid of a camera
and its accessories, and the
chemical process involved therein.
"Photograph" is the
mechanical and
chemical result of
Photography.
“Police Photography” study
of the general practices,
methods, and steps in taking
pictures of the crime scene,
physical things, that can be
used for law enforcement
purposes.
“Forensic photography”
application of photography
in criminal jurisprudence
and criminal investigation.
Uses In Law Enforcement
1. Records
2. Questioned documents;
3. Aerial photography;
4. Surveillance photography;
5. Detection of gunshot-powder burns, stains
and irregularities in cloth;
6. Detection of certain types of secret writings;
SPECIAL USES OF
PHOTOGRAPHY
Infrared
Photography
is the recording of
images formed by
infrared radiation.
ULTRAVIOLET
PHOTOGRAPHY
B
a.Joseph Niepce
b.George Shadbolt
c.George Eastman
d.Maddox
Micro-photography
- the production of
photographs
in which the image of
an objects is
reproduced much
smaller than it
actually is.
MUG SHOT
PHOTOGRAPHY
It is usually use for
personal
identification
which is the first
use of
photography in
police work.
X-RAY PHOTOGRAPHY
X rays are invisible
electromagnetic waves.
They behave much like
visible light. But they
can pass through things
such as wood, cardboard,
and flesh,
which light cannot
penetrate.
The Chinese were the
first people that we
know to write about
the basic idea of the
pinhole camera or
"camera obscura"
(Latin words meaning
"dark room").
Alhazen (965-1039) An Arabian
Scholar who found out that light
entering a small hole on the wall
or shuttered window of a darkened
room cast an upside down picture
of the scene outside onto the
opposite wall.
• Johann Heinrich
Schulze –
observed that
silver salts
darkened when
exposed to light.
• Joseph Nicephore Niepce, put a plate
coated with bitumen in a camera obscura.
He put the camera obscura facing his house
for eight hours and made a photograph. It is
the earliest camera photograph that we still
have today.
Henry Fox talbot
• Create permanent
(negative) images
using paper soaked
in silver chloride and
fix with a salt
solution.
(Calotype Process)
Niepce (left) began sharing his findings with Louis Jacques Mande
Daguerre (right), an artist who owned a theatre in Paris. They became
partners three years later. Daguerre's most important discovery came in
1835, two years after Niepce died.
Daguerre's process, which he named the daguerreotype, was
announced to the world on January 7, 1839. Half a year later the
French government gave Daguerre and Niepce's son, Isidore, a
lifetime pensions in exchange for all rights to their invention. The
daguerreotype was to become France's gift to the world.
R+B=M M+Y=R
R+G=Y M+C=B
B+G=C Y+C=G
R+B+G=W
OPTICS
Is the study of light. It is concerned with
the nature of light and the way it
behaves in optical instruments. Light is
a form of energy and so an object may
only produce light when there is energy
present. A red-hot piece of metal
receives energy in the form of heat and
converts some of it into red light.
Bending of Light
When travelling in open space, light
travels in straight line. However, when
light comes in contact with an object, it
may be bended in the following
manner:
1. Reflection
2. Refraction
3. Diffraction
Reflection is the
deflection or
bouncing back
of light when it
hits a surface.
Refraction is the
bending of light
when passing
from one
medium to
another.
Diffraction is the
bending of light
when hits a
sharp edge of an
opaque object
MEDIUMS OF LIGHT
1. Transparent objects – mediums that merely slow
down the speed of light but allow to pass freely in
other respects, transmit 90% or more of the
incident light.
2. Translucent objects –mediums that allow light to
pass through it in such a way that the outline of
the source of light is not clearly visible, transmit
50% or less of the incident light.
3. Opaque objects – A medium that divert or absorb
light, but does not allow lights to pass though.
THE RAT LAW
When incident light hits a medium,
three things might happen, the light
maybe:
A. Reflected
B. Absorbed
C. Transmitted
SOURCES OF LIGHT:
There are two sources of light,
they are known as natural and
artificial. Natural lights are lights
which come to existence without
the intervention of man and
artificial lights are lights which
are man made.
Classification of daylight
intensity
Bright Sunlight – a
lighting condition
where objects in open
space cast a deep and
uniform or distinct
shadow.
Hazy Sunlight –
objects in open
space cast a
transparent
shadow
Dull sunlight –
objects in open
space cast no
shadow.
atmospheric vapor atmospheric dust
MECHANICAL DEVICE
(CAMERA)
CAMERA
The principle of photography are
derived from science and the
images on the film or paper made by
the light rays through the camera
are dependent on the same general
laws which produces images upon
the retina through the lens of the
eye.
The essentials of any
camera, therefore, are
light tight box, a lens, a
shutter, and a holder of
sensitized material and
view finder.
Light tight box suggests an enclosure
devoid of light. An enclosure, which
would prevent light from exposing the
sensitized material inside the camera.
The lens to focus the light coming from
the subject. It operates more or less the
same way as the lens of the eye.
The shutter the control of the duration
of the exposure of the sensitized
material to light. The higher the
numerical value of the shutter speed
the shorter will be the duration of the
opening and closing of the shutter.
The holder of sensitized material to
hold firmly the sensitized material in
its place during exposure
VIEWING
SYSTEM shows
the photographer
the scene being
photographed.
Types of Camera
View Finder
Type
Considered as
smallest and the
simplest type of
camera.
Single Lens Reflex Camera
Type of
camera
best
suited for
police
work
Twin Lens Reflex Camera
Camera with
dual lens, one
for focusing
and the other
one for
forming the
image.
View or Press Type
Considered as
the biggest
and the most
sophisticated
camera. Used
in movie
making.
Divergent, Negative, or
concave lens - This
lens is always thinner
at the center and
thicker at the sides.
Light passing through it
are bended away from
each other as if coming
from a point.
Convergent, positive or
convex lens – this lens
is always thicker at the
center and thinner at
the sides, light passing
through it are bended
toward each other at
the other side of the
lens meeting at a point.
INHERENT LENS
DEFECT
SPHERICAL ABERRATION
inability of the lens to focus light
passing side of the lens
producing an image that is
sharp in the center and blurred
at the side
Coma – inability of the lens to
travel straight or lateral
Curvature of field – the relation
of the image are incorrect with
respect to one another
Distortion – defect in shape not
in sharpness
Chromatic Aberration
– inability of lens to
focus light of varying
wavelength. The lens
refract rays of short
wavelength and
therefore bring blue
rays to a shorter
focus than the red.
Astigmatism
– horizontal
and vertical
axis are not
equally
magnified.
Flares –
condition of
lens
producing
multiple
images
Classification of lens according to
degree of correctness
• Meniscus Lens – lens that has no correction
• Rapid Rectillinear Lens – lens corrected of
distortion
• Anastigmatic Lens – correcting astigmatism
• Apochromatic Lens – correcting both
astigmatism and chromatic aberration
FOCAL LENGTH -
The focal length of
a lens can be
define as the
distance from the
optical center of
the lens to the
focal plane when
the lens is set or
focused at infinity.
For a given film or sensor size, specified by the length of the diagonal, a lens may
be classified as:
NORMAL
LENS/MEDIUM
FOUCS - Lens with a
focal length
approximately equal
to the diagonal of the
film format
WIDE-ANGLE/SHORT
FOCUS - A lens with an
angle of view that is
wider than that of a
normal lens, or that of
the human eye. A wide-
angle lens has a focal
length which is less than
the diagonal of the film
format. The 24mm lens is a WIDE-ANGLE
LENS.
TELEPHOTO/LONG
LENS A lens with a
narrow angle of view,
a longer-than-normal
focal length, the
ability to magnify
images, and
exhibiting relatively
shallow depth of field.
Lens speed refers to the largest opening of the
diaphragm that the light can pass through it
determines the maximum intensity of the light
entering the light tight box.
A.FAST LENS – Lens with high lens speed, a
high lens speed is used during nightime or in
dark room.
B. SLOW LENS – lens with low lens speed,
used during daytime or where the room is very
bright.
RELATIVE APERTURE
The light gathering power of the lens expressed
in F-number.
DEPTH OF FIELD – is the range in front of and
behind a sharply focused subject in which details
also look sharp in the final photographic image.
HYPERFOCAL DISTANCE – nearest distance at
which when the lens is focused with a given
Particular diaphragm opening will gives the
maximum depth of field
Remember!
The lower the F number, the
bigger the lens opening, and the
bigger the lens opening the
greater the volume of light that
will passed through the lens and
will reach the sensitized material
FOCUSING
The setting of the proper
distance in order to form a
sharp image. The one that
controls the degree of
sharpness of the subject
PHOTOGRAPHIC FILM
A film consist basically, of a
random scattering of light
sensitive silver halides
suspended in a layer of animal
gelatin which is coated onto
acetate support or base.
Characteristic of Black and
White Film
EMULSION SPEED – the sensitivity of the film to
light; the extent to which emulsion is sensitive to
light.
The light sensitivity of the film is also known as
the FILM SPEED. Speed of the film is determined
through the numerical film speed labels given by
the film manufacturer.
Two classical speed ratings that became
popular:
ASA (American Standard Association) rating - This is
expressed in arithmetical value system. The speed in
numbers is directly proportional to the sensitivity of the
material. A film with an arithmetical value of 400 is four times
as fast as one with a speed of 100.
Medium View or
. General View or Long-range Mid-range