Forensic Photography Lecture 1 Introduction

Topics: Photography, Photographic film, Camera Pages: 12 (475 words) Published: April 27, 2015
Forensic Photography
Forensic: to be used in litigation activities
Photo: the use of light
Graph: to write, sketch, or graph
“To write with light for legal purposes”.

Three forms of Documentation
Notes
Sketches
Photography
All three rely heavily on visual stimulation for
input

Sketching was first:
The caveman and the wall drawings
The Egyptians and Hieroglyphics, a written
language using drawings

Notes are the use of symbols that code for thoughts
Photography records an image produced with light just as our eye records an image in our mind

Two scientific processes needed for
photography to happen
Creation of Optics
Light Sensitive response
Chemicals (Silver Halides)
Silicon Chips (CCD or CMOS)
Camera contains these items
Camera Obscura
Early Pin-hole camera with no film for permanently
recording an image

Pin-Hole Camera
Some cameras have no glass optics

Pin-Hole
Camera Picture
Focal Length: 125mm
Pinhole: 0.5mm
Exposure Time: 3 seconds

 Super Wide Angle
Equivalent to a 18mm lens
on a 35mm camera.

 Wide Angle
Equivalent to a 27mm
lens on a 35mm camera.

 

  Normal or 1:1
Equivalent to a 55mm
lens on a 35mm camera.

  Telephoto
Equivalent to a 82mm
lens on a 35mm camera.

 

 

The Light Sensitive Media
Light interacts and creates chemical change
The changes are not all sufficiently:
Sensitive
Permanent
Early successful media used wet silver halides process:
Daguerreotype: a positive on copper
coated with a thin layer of silver
Calotype: a paper negative that could be used to
create a positive. Useful for making copies
Silver halides continue to be the chemicals used to create the latent image in modern films

The Light Sensitive Media
Many improvements were made
Collodion process: a wet process that reduced exposure
times to two or three seconds and was cheaper
Wet process required a considerable amount of equipment
on location
Dr. Richard Maddox used Gelatin as a basis for the photographic plate. This led to the development of the dry plate
The dry-plate process allow plates to be made and used at any time
This allow media to be made in bulk at a factory, used at a
later date, and processed at another time and location.
Celluloid (1860) allowed George Eastman to introduce a flexible film for his box camera and Eadweard Muybridge to pave the
way for motion picures

George Eastman’s Box Camera

The Light Sensitive Media
The flexible film changed from the cellulose nitrate of the late 19th century through the triacetate films to the modern day
plastic films
The first flexible movie films measured 35mm and this film
was used for still cameras in the early 20s
120 roll was developed in the late 20s and was use in Kodak
box and Brownie cameras as well a professional cameras
Kodachrome color film was developed in 1935 an used dyecoupled colors in three layers to create an apparent color image

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