Photography: Intro, History, Basic Camera Function Flashcards
How do photographs assist in a forensic investigation, specifically in relation to the crime scene?
3
Accurately depicts scene as it appeared upon arrival
Provides visual for investigators, witnesses, victims, and judiciary to understand the scene
Metaphorically puts people into the scene
What could alter a crime scene between the crime and the arrival of forensic investigators?
6
- Weather
- Clean up
- Victim
- Animals/insects
- First responders
- Time (degredation, sun, UV, decomp)
Aside from the benefits for scene investigation, how else can photography aid forensic investigators?
6
- Locating tool (suspects, missing persons, property)
- ID suspects
- Disaster victim ID
- Charting for court
- Safe and acceptble alternative to display contaminated, hazardous or dangerous evidence
- Disclosure requirements
Outline the three main types of photographs that need to be taken to document a crime scene.
- Overall scene description (4 corners)
- Midrange of particular points of interest
- Close up of minutiae, fine detail
What is photography?
The art or process of producing images by the action of radiant energy and especially light on a sensitive surface (e.g., film, optical sensor)
When was the camera obscura created?
17th century
What was an alternative name for the camera obscura?
Dark Chamber
Describe how the camera obscura worked
- Consists of box or room with hole in one side
- light from external scene passes through hole and strikes surface inside
- Image is rotated 180 degrees, perspective and colour preserved
- Can be projected onto paper then traced
What did Isaac Newton discover in 1666?
Divides sunlight with a prism and discovers that white light is composed of seven distinct colours
What did Prof. J. Schulze contribute to photography?
Mixed chalk, nitric acid and silver in a flask and noticed darkening on side of flask upon exposure to light.
Who is credited with creating the first photo-sensitive compound? When?
Prof. J. Schulz in 1727
What was the first practicable photographic process?
Daguerreotype
Outline the Dagguerreotype process.
5
Using camera obscura, a light tight plate holder was designed to hold a copper plate faced with a thin layer of silver.
Prior to exposing the plate in the camera, it was made light sensitive by iodine crystal fumes.
After exposure, mercury fumes would develop the image.
Image was then fixed in a sodium chloride solution
The plate could be toned in gold chloride
When was the Dagguerreotype developed?
19th century
Who developed the Dagguereotype?
Nicephore Niepce and Louis-Jacques-Mande Daguerre
What was the Calotype and what was its significance?
A more sensitive photographic process that reduced exposure time
Outline the process of the Calotype.
4
- Paper soaked in silver nitrate and potassium iodide, rinsed in solution of gallic acid and silver nitrate
- Exposure
- Latent image developed in gallic acid solution
- Positive print created by contact printing onto another sheet of light sensitive paper
Who was the first person to use the phrase “photography” and when did this occur?
Sir John Herschel in 1839
Who founded the Eastman Kodak Company?
George Eastman
What was the significance of the founding of the Eastman Kodak Company?
Popularized the use of roll film, helping to bring photography to the mainstream.
When did Eastman found the Eastman Dry Plate Company?
1880
Who founded the Polaroid camera?
Edwin Land
When was the Land Camera first introduced and when did its production begin?
1947, 1948
What was the significance of the invention of the Polaroid camera?
No longer needed to take film to be developed
When was the still video camera invented and by whom?
By Sony Mavica in 1981
When did Kodak scientists invent the world’s first megapixel sensor?
1986
When was the Kodak Photo CD invented?
1992
When was the first digital camera invented and by whom?
1995 by Kodak
What was the name of the first camera phone and when was it invented?
Sharp J-SH04 in 2000
When was the first iPhone released?
2007
When did Polaroid discontinue all film production?
2008
What did Polaroid cite as the reason for them discontinuing film production?
Digital technology
At what speed does light travel in a vacuum?
300,000 km/sec
What portion of the EM spectrum consists of visible light?
400-700 nm
What four things can happen to light when encountering a medium?
- Reflect
- Refract
- Diffuse
- Blocked/absorb
What property of light do lenses use to form images on the camera sensor or film plane?
Refraction
What are the most common types of material used in film photography?
Silver halides
What is the photo-sensitive material in digital photography?
2
Charge coupled device (CCD)
Complimentary metal-oxide-semiconductor (CMOS)
Describe how CCD and CMOS generally work.
2
Generate small current or alternate photo site charge in response to light.
Current/charge converted to digital information and saved on memory card.
Describe how a camera works when you are looking through the viewfinder but not taking an image.
4
- Light enters lenses
- Strikes mirror
- Reflected light bounces off pentaprism
- Reflected viewfinder image produced
Describe how a camera works when taking a picture
4
- Light enters lens
- Light condense and focused to hit sensor
- Shutter curtain opens and mirror lifts when shutter button clicked
- Light strikes sensor
What is aperture?
The lens diaphragm opening inside a photographic lens
What does aperture do?
Regulates the amount of light passing onto sensor
What is aperture control expressed in?
f-stops
What is the advantage of the f-stop system?
When set to same f-number, all lenses pass same amount of light regardless of focal length
How does each f-stop affect the amount of light passing through the lens?
Changes by factor of 2 (doubled or halved)
Describe the relationship between f-stop, aperture size and light passing.
Lower f-stop = larger aperture = more light entering camera
List the typical f-stops from largest to smallest aperture
10
f/1.4
f/2
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22
f/32
What can the function of the aperture be compared to?
Pupil function
What is shutter speed?
Enables light to pass through to CCD for specific length of time
Describe the relationship between shutter speed and aperture.
Reciprocal
Which affects depth of field: aperture or shutter speed?
Aperture
What does the bulb shutter speed do?
Holds camera shutter open until the shutter trigger is released
In what circumstances are shutter speeds from B to 1/30 used?
2
- When there is no movement in the image and more light is required for proper exposure
- When there is movement in the image and the photoprapher wants to portray the movement by blurring the subject
What equipment is needed when using shutter speeds from B to 1/30?
Tripod
Whatis the smallest shutter speed that most people can stabilize the camera at without making the image blurry?
1/60
List the standard shutter speeds from slowest to fastest.
13
B
1
1/2
1/4
1/8
1/15
1/30
1/60
1/125
1/250
1/500
1/1000
1/2000
