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Hottawa Stuff > Week 1 > Flashcards

Week 1 Flashcards

1
Q

Digital Camera Sensor - Describe

A

A matrix of millions of microscopic light sensitive photodiodes

These create pixels by sensing light intensity

Do not record colours, only intensity of light (grey scale)

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2
Q

2 types of digital camera sensors

A

CCD - solid state sensor called Charge Coupled Device

CMOS - Complementary Metal Oxide Semiconductor - Nikon uses this

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3
Q

Exam Question

Pixels - define and name 3 properties

A

Pixel = Picture Element

A digital square composed of a number value based on the intensity of light received from a sensor

3 Properties:

  • Location
  • Colour Value
  • Size
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4
Q

File formats - Loss of Information

A

Common formats

  • JPEG
  • TIFF
  • RAW

TIFF & PSD files do not lose detail; TIFF is a very large file size; lossless

RAW is uncompressed, but an enhanced image cannot be saved in RAW format; use this format when you are enhancing a file

JPEG takes up less space, easily shared, but loses information when saved; each change/save further compresses file; lossy file

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5
Q

File size of images - affected by…

A

1) Number of pixels
2) Colour Depth
- 8, 12, 14, 16 bit per channel

3) Colour Mode
- CMKY (4 channels)
- RGB (3 channels)
- Grayscale (1 channel)

4) File Format
- RAW (lossless)
- JPEG (lossy)
- TIFF (lossless)

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6
Q

Exam Question

Image Quality - Factors that affect

A

Resolution
Colour bit depth (16 bit vs 8 bit)
Lens (quality of)
Size of CCD (full frame vs crop)
File format (JPEG, RAW, TIFF)
Colour interpolation (how colour is processed)
Processing of image(changes made; contrast, etc)

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7
Q

3 layers of human skin

A

Epidermis

Dermis

Hypodermis

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8
Q

Epidermis

A

Outermost layer

  • Composed mainy of keratinocytes
  • protective barrier
  • reduces water loss through evaporation
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9
Q

2 Types of Skin

A

Smooth skin:

  • has hair
  • Sebaceous glands (greastest around head/face)
  • NO friction ridges

Volar (FR) skin:

  • only sweat glands
  • completely covered in ridges (no voids)
  • fingers/palms & bottoms of feet
  • sweat of FR skin increases grip
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10
Q

Describe the Basement Membrane

A

Between Dermis & Epidermis

  • Fibrous sheet
  • fibres are interwoven
  • structural support for epidermis
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11
Q

5 Layers of Epidermis

A

1) Stratum Corneum
2) stratum Lucidum
3) stratum Granulosum
4) stratum Spinosum
5) stratum Basale

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12
Q

Stratum Basale

A

Last layer - CLGSB

  • single layer of columnar shaped cells
  • mitosis - the generation of new cells (cells split)
  • new cells pushed towards surface
  • are blueprint of what you see on the surface
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13
Q

Stratum Spinosum

A

2nd Last layer - CLGSB

  • 2-4 cells thick
  • exhibit first changes in cell structure
    Synthesis of keratin process
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14
Q

Stratum Granulosum

A

Middle layer - CLGSB

  • Last of the living cells
  • first precursors of keratin
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15
Q

Stratum Lucidum

A

2nd layer - CLGSB

Keratin fills inside of cell

Keratin is an insoluable protein

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16
Q

Stratum Corneum

A

1st layer - CLGSB

  • Up to 100cells thick
  • cells have accumulation of Keratin
  • cell death has occurred
  • cells large and flat
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17
Q

Dermis

A 
Middle layer
Made up of:
- cells, fibres, blood vessels and gelatinous material
- energy reserve of Epidermis
- sensory reception
- temperature regulation
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18
Q

Desmosomes

A

Protein Bundles that keep cells together as they migrate from the Basale to the surface

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19
Q

Why is friction skin unique and persistent?

A

Persistency:

1) Basal Cell Mitosis
2) Structural Elements

Uniqueness:

1) Random timing
2) Random growth
3) Random pressures

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20
Q

Describe Basale Cell Mitosis

A

Occurs in Basale layer of epidermis.

Is blueprint for cell regeneration

Cell replicates, splits, moves up through epidermis to surface

Can take up to 30 days

Stay together with Desmosomes

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21
Q

What are the 4 structural elements relating to persistency

A

1) desmosomes bind newly formed cells together until they reach surface
2) basale cells (bottom of epidermis) attached to bsmt membrane with Fibrils/microfibrils and hemidesmosomes
3) bsmt membrane attached to dermis with fibrils/microfibrils
4) surface of dermis, dermal papillae fit into ‘pockets’ of underside of epidermis beside PR’s

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22
Q

Desribe uniqueness of FR skin

A

1) Random timing:
- PR’s develop during 10.5-12 weeks
- volar pads regress
- time of differentation occurs
Ie: end of PR development, SE develoment occurs

2) Random growth:
- # of ridge units that form a FR
- path a FR takes
- Start/stop of FR
- Thickness/thinness of FR
- alignment, bifurcation or misalignment of FR
- height of a ridge
- size and location of pores

3) Random Pressures
- stress on the skin surface can affect size and shape of volar pads
- pressures in the womb
- neighboring ridges
- genetic & physical pressures

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23
Q

Dermal Papillae (Papillary Pegs)

A

Peg like projections on top of dermis, that fit into pockets on the underside of epidermis

Run in 2 rows between PR & SR; hug PR

Increase surface area of attachment between dermis and epidermis

Break down into smaller units due to aging

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24
Q

Whose extensive research of fetal skin cross sections showed the development of dermal papillae?

A

Alfred Hale 1952

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25
Q

Whose research showed the dermal papillae are in 2 rows ok the underside of the epidermis and break down as people age?

A

Michio Okajima 1976

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26
Q

Describe scars

A

Permanent damage to the basal layer or beyond

  • cuts
  • genetic condition (diseases)
  • may appear as voids or partial voids

Damages the ‘blue print’ - basal layer

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27
Q

Friction skin development (fetal)

A

3 weeks:
- epidermis is 1 cell thick

6 weeks:

  • hand is paddle like
  • volar pads appear (transient bulges of tissue) on palms/fingers
    • 5 on fingers, 4 on interdigital, 1 on thenar & 1 on hypothenar area of palm

8 weeks:

  • digits have seperated
  • thumb has rotated
  • flexion creases appear (first on palm, then fingers)
  1. 5 to 12 weeks:
    - volar pad regression
    - PR on underside of epidermis begin to form as result of rapid cell division of basal cells
    - longest ridges & bifurcations form first
    - later in develop, less area to cover, short ridges (islands/dots) appear

15-17 weeks:

  • secondary ridges begin to appear
  • form between existing PR
  • PR develop ceases in that area
  • Time of Differentation!!!

20 weeks:

  • SR locations are established
  • FR are visible on surface
  • Final FR config is established & will not change by week 20 (as early as 16 weeks)

20-24 weeks:

  • SR develop of same depth as PR (into the dermis)
  • 23 weeks dermal papillae form on top of dermis between PR & SR hugging PR
  • 24 weeks entire system mature
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28
Q

Who described the evolution of the friction ridge skin of mammals including that mammals have the same arrangement of volar pads on the hands and feet?

A

Inez Whipple 1904

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29
Q

3 types of Flexion creases

A

Digital Transverse Crease
- top

Proximal Transverse Crease
- middle

Thenar Crease
- bottom

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30
Q

Whose extensive research on friction ridge skin showed volar pad regression occurs almost concurrently with the beginning of primary ridge development?

A

Harold Cummins 1929

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31
Q

Whose study of thin cross sections of fetal skin determined the timing and development of primary and secondary ridges?

A

Alfred Hale 1952

32
Q

Who was the first to suggest these centers of disturbance of primate friction ridge skin formations represents the locations of the volar pads?

A

Harrison Hawthorne Wilder

Early 20th century

33
Q

What affects pattern types?

A

The size shape and symmetry of volar pads direct ridge flow and thus pattern formations

The timing between the start of PR development and volar pad regression affects ridge count (core to delta distance)

  • Early ridge development = higher volar pads (less regression) and higher ridge count/core-delta distance
  • PR development after volar pad mostly
    regressed = low ridge count/core-delta distance
34
Q

Whose extensive research of friction ridge skin showed the size, location, growth and configuration of the volar pads affect friction ridge develop and the overall fingerprint pattern?

A

Harold Cummins 1929

35
Q

Ridge Formation - Occurence order

A

1) top/apex of volar pad
2) tip
3) base (platform ridges)

3 can be used for digit orientation, as they are generally horizontal ridges

36
Q

Volar Pads and Patterns

A

1) Large even shaped volar pads = circular type patterns (whorls)

2) Volar pads offset to one side = loops
- height of the volar pad dictates core to delta distance

3) PR develop much later in process after volar pads have fully regressed (low/small volar pads) = arch/tented arch

37
Q

Minutiae - Gaulton Points

A

1) FR made up of individual ridge units
2) Each ridge unit contains: pore, pore duct & sweat gland
3) length of ridge unit is ~same as its width

38
Q

Who is credited with being the first to recognize that although specific friction ridge arrangements may be similar, they are never duplicated?

A

JCA Mayer 1788

39
Q

Incipient Ridges

A

Correspond to PR

Immature ridge

Did not have time to fully develop prior to start of SR develop ( T of D)

Based on same structure of mature PR’s

Thinner than mature ridge

Usually do not have developed pore

40
Q

Who studied incipient ridges and determined they are primary ridges that did not fully develop?

A

Michio Okajima 1976

41
Q

Define Ridgeology

A

The study of uniqueness of the friction skin and its use for personal identification.

42
Q

3 basic pattern types

A

Arches

Whorls

Loops

43
Q

3 main areas of the palm

A

Interdigital

Hypothenar

Thenar

44
Q

3 main creases of the palm

A

Digital Transverse crease

Promixal Transverse crease

Thenar crease

45
Q

Ulna and Radial bones

A

Ulna is on the little finger side

Radial is on the thumb side

46
Q

Image quality on camera determined by…

A

ISO

Shutter Speed

Aperature

Aperature Priority is the preferred setting on our cameras

47
Q

What does CSWIM stand for?

A

C = Compensation

S = Size (Quality)

W = White Balance (light source setting)

I = ISO (higher = digital noise)

M = Metering (turn back to Matrix each time)

48
Q

Resizing in Photoshop does…

A

Changes the number of pixels per inch (PPI)

Physical size of the image changes, but the total number of pixels remains the same

The pixels rendered become larger or smaller, have the same colour and location info

49
Q

Re-sampling an image in photoshop does…

A

Changes the number of pixels in an image

Allows the size of an image to remain constant

50
Q

Calibration

A

Method of resizing an image so that it correlates to an actual given value (measurement)

Must have a properly photographed scale present

51
Q

Differential Growth - Friction Skin Development

A

The random growth aspects of friction skin development that occurs from the onset of Primary Ridge development (10.5-12 weeks) until the appearance of Secondary Ridge development (15-17 weeks; Time of Differentation)

52
Q

Preferred camera mode for Forensic Photography and why?

A

Aperature Priority so you can control the amount of Depth of Field

53
Q

Why do we calibrate images

A

1) to look professional in Court
2) to enhance the image
3) to print the image life sized

54
Q

Described the formation and development of volar pads on the human fetus. Found that volar pads regress at the same time friction ridges develop.

A

Harold Cummins

55
Q

Found that all mammals have the same morphological arrangement of the formation of friction ridges. Found that ridge patterns are affected by external forces and pressures by neighbouring developing ridges

A

Alfred Hale

56
Q

Described the anatomical formation of friction ridges. Established uniqueness by detailing how ridge units are subjected to differential growth

A

Inez Whipple

57
Q

Detailed the various stages of friction ridge development, particuarly how the primary and secondary ridges are formed. Detailed the developement of papillary pegs and major ridge path deviations

A

Harrison Hawthorne Wilder

58
Q

F Stops - Aperature

A

1) Controls the volume of light
2) Controls the depth of field

Smaller the number

  • More light = Less depth of field
  • Moving up 1 stop halves the light

Larger the number

  • Less light = More depth of field
  • Moving down 1 stop doubles the light

F/2.8, F/4, F/5.6, F/8, F/11, F/16, F/22, F/32

59
Q

Shutter Speed

A

Controls the amount of time the sensor is exposed to light

Displayed as seconds and fractions of seconds

1”, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500

Moving up 1 stop halves the light

Moving down 1 stop doubles the light

60
Q

Polarizing filters

A

Filter that transmits light rays in one direction

Used to eliminate glare

61
Q

Channels (Contrast Filters)

A

Selected channel will allow own colour to pass while blocking other colours

Used to create contrast, greatly beneficial for fingerprints between the impression and the background

62
Q

Colour Models/Modes

A

Mathematical representation of colour values which gives a set of colours

Main colour models we use; RGB and CMYK

Used to give the best contrast between an inpression and a background.

CMYK used primarily for Ninhydren as you cam select the colour Majenta

63
Q

RGB Colour Model

A

Additive model

Transmitted

Primary colours: Red, Green and Blue

All 3 together create white

In RGB, red lightens red, etc

64
Q

CMYK Model

A

Subtractive model

Reflected light

CMYK: Cyan, Magenta, Yellow and K(Key)

Mixing all 3 creates black

Cyan darkens Cyan, etc

65
Q

Tonal Ranges

A

1) Highlights
2) Midtones
3) Shadows

66
Q

ISO

A

Light sensitivity of the sensor

100, 200, 400, 800, 1600, 3200, 6400, etc

Higher the ISO, creates digital noise (reduced quality of an image)

67
Q

Camera Lens

A

Gathers light rays and brings them into focus on the sensor

68
Q

Increasing Depth of Field

A

1) Use a SMALLER Aperature (larger number)

2) Increase camera to subject distance
- Move away from subject!

3) Use a SHORTER focal length

69
Q

Hand Held and Motion Blur

A

The Shutter Speed should equal the reciprocal of the chosen Focal length

200 =

100 =

50 =

70
Q

Metering Modes

A

1) Matrix
- Everything

2) Center weighted
- Focus on the object in the center

3) Spot
- Focus on a central spot in the center

71
Q

Manual Focus - Used when

A

1) Night photography
2) Close-up photography
3) Fingerprint photography

72
Q

Inverse Square Law

A

The intensity of light reaching an object is inversely proportional to the square of the distance between the object and the light source

1 = 1
2 = 4
3 = 9
4 = 16
5 = 25
6 = 36
Etc...
73
Q

Flash

A

Referred to as a Speedlight

Can be attached to the ‘hot shoe’

Can be attached via flash sync cord

Can be triggered remotely

74
Q

Flash Modes

A

Synchronized flash

Slow sync flash

Rear curtain sync

75
Q

Flash Techniques

Exam Question

A

Direct flash

Oblique/grazed

Feathered

Bounce

Flill (lightens up shadowed areas!)

76
Q

Perspective

A

Where the camera was positioned when a photo was taken

Changing focal length does not change perspective, changing location does

50mm is what a person saw/witnessed

Picture angle of 46 degrees

Most appropriate for forensic photography for depicting what a witness saw

Focal length is equal to the diagonal of the sensor

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