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Forensics Y2 > Photography > Flashcards

Photography Flashcards

1
Q

What camera filter isn’t used in CSI

A

Neutral Density Filter

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2
Q

What does a neutral density filter do?

A

Blurs Motion

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3
Q

What does a close up filter do?

A

Increases magnification

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4
Q

What does a polarizing filter do? (3 answers)

A

Enhances colour, stops reflections, darkens darks

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5
Q

What does a UV filter do? (2 answers)

A

Blocks UV rays, protects lens from damage

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6
Q

When to not use autofocus

A

Marks photography

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7
Q

What is aperture?

A

The opening of a camera’s lens which light passes to enter camera body

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8
Q

What is ISO?

A

The sensitivity of the camera to available light

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9
Q

When would you use a high ISO?

A

Taking photos in low light conditions without a flash

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10
Q

What can high ISO lead to?

A

More digital noise/grain

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11
Q

What is shutter speed?

A

Length of time a camera’s shutter is open

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12
Q

What can a fast shutter speed do?

A

Freeze motion

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13
Q

What can a slow shutter speed do?

A

Motion blur

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14
Q

What affects depth of field?

A

Aperture, focal length, camera to subject distance

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15
Q

What affects exposure?

A

Aperture, Shutter speed, ISO

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16
Q

What is the inverse square law?

A

Intensity of light decreases as distance increases

Intensity of light decreases with the square of distance from the source

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17
Q

What mm is natural field of view?

A

50mm

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18
Q

Consequence of larger focal length

A

Narrower field of view

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19
Q

Consequence of smaller focal length

A

Wider field of view

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20
Q

Consequence of far camera to subject distance

A

Deep depth of field

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21
Q

Consequence of close camera to subject distance

A

Shallow depth of field

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22
Q

Minimum shutter speed for a hand held camera

A

1/30

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23
Q

What is DSLR?

A

Digital single lens reflex

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24
Q

What does a small aperture do? (DOF)

A

Greater depth of field

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25
Q

What does a large aperture do?

A

Shallow depth of field

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26
Q

What to record at a firearms scene? (7)

A

Weapons
Position of shooter and direction
Empty cartridge cases
Bullet strikes
Surfaces of impact
Ricochet impact points
Damage caused

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27
Q

What lens may be useful when photographing bullet strikes?

A

Close up filters/macro lens

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28
Q

What to remember when photographing Bullet Strikes? (2)

A

Images on same plane/perpendicular
Measurements written on labels (distances)

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29
Q

What is needed before handling firearms for photography?

A

Firearms officer to declare safe

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30
Q

What individual features of ballistics to photograph? (4)

A

Headstamp contains info
Serial numbers
Condition of weapon
Presence of blood or tissues

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31
Q

How to reconstruct a ballistics scene for photography? (6)

A

Position of firer
Position of cartridge cases
Lines of sight
Ricochet impact sites
Impact sites
Trajectories using lasers

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32
Q

What are trajectory rods/what do they do?

A

Placed into impact sites to show the direction of the bullets origin

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33
Q

What to know for laser reconstruction for ballistics photography? (3)

A

Indicates approximate trajectories
Position of firer MUST be known
Requires low light

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34
Q

What kind of exposure would be needed for laser reconstruction of ballistics photography?

A

Long exposure / long shutter speed on a tripod

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35
Q

How does fluorescence photography work?

A

UV enhances fluorescence, propels evidence into visual part of spectrum

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36
Q

What is needed for blacklights to be used? (4)

A

A slow shutter speed
High ISO
Tripod may be needed for marks photography
Low light

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37
Q

What photography technique do you use with a blacklight?

A

Painting with light

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38
Q

What is an issue faced with UV and body fluid photography?

A

Many backgrounds fluoresce, so lights and filters may be needed

39
Q

What is ALS? (& example)

A

Alternative light sources, (crime lights) (high intensity light sources)

40
Q

Why is bloodstain photography important?

A

Images give context to individual stains, as well as angles and sizes

41
Q

How to establish perspective or context with a bloodstain image

A

Zoomed out, mid shot, zoomed in shot

42
Q

What to remember about bloodstain images?

A

Need to be on same plane or image distorts

43
Q

Different types of blood marks (4)

A

Arterial Spurting
Transfer marks
Pooling
Swipe patterns

44
Q

How to over-expose an image? (5)

A

Open aperture
Slow shutter speed
Increase ISO
Increase flash output
Use exposure compensation dial

45
Q

When is HDR used?

A

When you cannot control the light in difficult lighting circumstances

46
Q

What 2 images do you need to take for HDR?

A
  1. Image with correctly exposed highlights - shadows have no detail
  2. Image with correctly exposed shadows - highlights have no detail
  3. Both images combined to make new image perfectly exposed
47
Q

What is a UAV?

A

Unmanned arial vehicle

48
Q

Advantages of using UAVs? (8)

A

Cheap
Fast
Can get closer
Can work in unsafe areas
Can use IR and thermal imaging cameras
Easy to use
Can capture scene from above
Allows more context

49
Q

Disadvantages of using UAVs? (6)

A

Licence required
Rules of flying
Usually 25 mins or shorter battery life
Cannot change lens
No zoom
Must retain sight of drone

50
Q

Some rules for flying a drone (5)

A

Can’t fly above 120m
Can’t fly within 50m of people/property
Can’t fly within 150m of congested areas
Must keep sight of drone
Not flown near airfields

51
Q

Consequence of not following drone rules

A

£2500 fine or 5 years imprisonment

52
Q

What do you need to wear at a fire scene?

A

Helmet
Steel toe capped boots
Slash resistant gloves
Overalls

53
Q

Challenges when photographing fire scenes (4)

A

Poor lighting (too much daylight/night-time)
Lack of contrast
Flash can bounce of smoke
Difficult to focus in low light

54
Q

3 Techniques that can be used in fire scenes?

A

Open flash
Painting with light
HDR

55
Q

How to avoid lighting problems with fire scenes (3)

A

Combine artificial light with ambient light
ISO
Focus manually using a torch

56
Q

What to photograph at a firearm scene? (8)

A

Scene
Evidence
Weapons
Position of shooter and direction
Empty cartridge cases
Bullet strikes
Surfaces of impact
Damage

57
Q

What to use UV photography for? (7)

A

Fingerprint enhancements
Forgery/document alterations
Fibres/trace evidence
Presence of security fluids
Body fluids
Bruises and bite marks
Gunshot residue

58
Q

False positive for a black light?

A

Clothes and washing powders

59
Q

How long after an incident can you take an image of a bite mark with UV?

A

6 weeks

60
Q

What to consider when using a small aperture with UV photography?

A

May require more time

61
Q

What is required to use ALS?

A

Low light conditions

62
Q

How to photograph Luminol?

A

1 image normal light, 2nd with luminol, no flash, low light conditions

63
Q

What background is difficult to use when photographing crimes?

A

White backgrounds - camera may darken image to prevent what it thinks is overexposure. Prevent this by changing exposure

64
Q

How to take images for HDR?

A

Manual
Only changing shutter speed to change exposure (slow down to expose shadows, speed up to expose highlights)

65
Q

How to make sure you don’t damage a drone? (3)

A

Clearance of 100degrees from buildings prior to take off
Not flown in high winds
Not flown with damaged propellers/equipment

66
Q

Why are drones used at crime scenes?(3)

A

Photograph high points of entry
IR and thermal
1st on scene

67
Q

What to consider when entering a fire scene? (Investigative) (3)

A

Cause/seat of fire
Structural damage/damage from firefighters
Missing persons or fatalities

68
Q

What to be aware of when photographing fire scenes? (5) (any dangers?)

A

Reignition
Damage
Biohazards and pathogens
Drugs/firearms/explosives
Gases&vapours/ soot/dust

69
Q

What can be released from vehicles which we may need to be aware of, especially at fire scenes?

A

Hydrofluoric acid - can dissolve skin and bone. Released by rubber seals, gaskets etc

70
Q

How to photograph darkened areas without over exposing light areas? (Fire scenes)

A

Use a weak flash

71
Q

What can UV not be seen under?

A

400nm on the electromagnetic spectrum (part of the visible light segment of the spectrum)

72
Q

Some common sources of UV

A

Sun, tanning tubes, Crime Lights (ALS), Incandescent lightbulbs

73
Q

What does fluorescence do to UV in the electromagnetic spectrum?

A

Propel potential evidence into the visible part of the spectrum (400-700nm)

74
Q

How to measure the angle of impact of a bloodstain?

A

SINE = width/length

75
Q

What is bit depth?

A

Refers to the amount of detail captured per pixel/image. (Normally 8 bit but can increase to 16 or 32 in PS)

76
Q

What height can you not fly a drone higher than?

A

120m

77
Q

How much of a distance must a drone be from people or property?

A

50m

78
Q

How much of a distance must a drone be from congested areas?

A

150m

79
Q

Wind limit for flying drones

A

12mph/19kph

80
Q

What other personnel may be involved in a fire scene?

A

Local Authorities, environment agency, structural engineers, contractors, scientists, insurance

81
Q

What to be cautious about at a vehicle fire?

A

Hydrofluoric acid (HF) released by rubber seals, hoses and gaskets. Rapidly dissolves skin and can cause gangrene leading to amputations (HF antidote gel to prevent)

82
Q

What is crocodiling?

A

Damage created by fires, typically on wood.

83
Q

What light technique would you use at a fire scene?

A

Open flash

84
Q

What light technique would you use with UV lighting?

A

Painting with light

85
Q

Pros of using 360 photography

A

Photographer not required to photograph everything, viewer can look where they please, immersion

86
Q

What is the nodal point?

A

The optical centre of the lens. Evens out lens distortion that arises when the camera chip is in the centre of rotation.

87
Q

What is parallax error?

A

When nodal point not correctly found. Foreground and background move separately to each other and appear displaced when camera is rotated. When images are stitched together, images will not overlap perfectly and errors will appear.

88
Q

What issues to look out for with 360 degree photography?

A

Parallax error

89
Q

What to photograph at PM?

A

Full body shots of front and rear, body bag, ID/labels/ security tags,items

90
Q

What kind of lens would you use for pm photography and why?

A

Wide angle lens to overlap images

91
Q

How does aperture affect depth of field?

A

Wide aperture will give shallow depth of field, whereas a narrow aperture will give a deep depth of field

92
Q

How does focal length affect depth of field?

A

Short focal length, wide depth of field
Long focal length, narrow depth of field.

93
Q

How does camera to subject distance affect depth of field?

A

Close distance, narrow depth of field
Further away, wider depth of field

94
Q

Why is a white sheet used?

A

Diffuses the light,
Softens and reduces shadows
Set white balance so exposure can be correct for the rest of the image

Forensics Y2 (7 decks)

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