Photography

Question 1

What is the role of the CSI?

Answer 1

• Locate
• Record
• Recover

Question 2

How do you record an incident?

Answer 2

1. Video first
   - briefing -> SIO for team
   - scene recording -> start to finish
   - 360 degrees
2. 360-degree images
   - looms of significance
   - video/still

Question 3

What should a CSI record?

Answer 3

Permanent visual record - record and document evidence in situ
- scene
- court illustration
- critical findings
- lab based
- injury based

Question 4

What is the 2021 audit trail?

Answer 4

• camera -> lenses
• flash -> filters
• lighting
• ABFO measuring scales
• unique identifying number
• date/time
• lighting conditions
• distance
• use of flash
• exposure settings
• apertutre settings

Question 5

What does a DSLR do?

Answer 5

• can change lenses
• exposure and focus are key
• light -> aperture vs shutter speed
• manual vs automatic

Question 6

What does Films - traditional SLR do?

Answer 6

• black and white
• colour

Question 7

How is light sensitivity measured using the ISO scale?

Answer 7

• higher the number, faster the film develops an image
• slower the rating, the less grainy the image
• typical rating is ISO200/24 degrees

Question 8

What is CCD technology?

Answer 8

CCD - Charged couple device
- shutter opened
- light enters and hits an array of light sensitive cells on a silicon substrate (amount absorbed dependant on amount of light)
- converts this ‘light’ to electrical charge and reads this change (proportional to the amount of light absorbed) across the array - each cell is viewed as a pixel and colour detected by combinations of these colour

Question 9

How do you save file types?

Answer 9

• RAW - no compression
• JPEG (joint photographic expert group) - compressed
• TIFF (tag image file format)
• GIF (graphic interchange format)
• BMP (bitmap)
• PNG (portable network graphics)

Question 10

How does technology work when it’s moved to mirrorless?

Answer 10

• shutter opened = light
• no mirror to reflect light, faster frame rates, autofocus faster (no mirror in the way) and more focus points
• electronic viewfinder displays digital projection - sensor sizes comparable to dSLR

Question 11

How are images stored on a camera?

Answer 11

• xD
• SD
• MMC
• Direct to disk
• Flash drives

Question 12

What are the important camera parts?

Answer 12

• Focal length
• Focussing ring
• Apeture ring

Question 13

What are the types of lenses?

Answer 13

• Normal
  Equivalent to the same angle of view as the human eye
• Wide angle
  Typically angle of view 63 degrees to 94 degrees
  Can extend to 180 degrees
• Telephoto
• Zoom
• Macro

Question 14

What is focal length?

Answer 14

Standard lens is 50 mm
Controls the:
- magnification of the image
- the angle of view that it covers

Lens type influences focal length.

Question 15

How can the size of an image be altered?

Answer 15

• Reducing focal length makes image smaller but increases a greater angle of view
• Increasing the focal length increases the size of the image and reduces the angle of the view

Question 16

What is macro photography?

Answer 16

Close up
- most lenses cannot focus closer than 0.5m - tripod for stability
- to photograph small objects close up you need one of the following:
a) macro lens
b) close up ‘filter’
c) extension tube

Question 17

What do you use when photographing enhanced fingermarks?

Answer 17

1:1 scale
- specialist lighting

Question 18

How doe slighting and sensitivity affect photography?

Answer 18

Intensity - important in context of correct exposure - shutter and aperture
Colour - overhead lighting vs natural light

Question 19

What is sensitivity in regards to ISO ratings?

Answer 19

• typically 100-6400 - controls brightness of image
• each increase doubles brightness but increases the noise - grain/colour
  Range - 100, 200, 400, 800, 1600

Question 20

Where to start with ISO?

Answer 20

• lots of light = low ISO
• even in low light you can still use a low setting -> depends on shutter speed/aperture

e.g. can let more ligth in by opening the shutter for longer or having a wider aperture

Question 21

What is the order of setting up the camera?

Answer 21

1. set your aperture
2. Adjust shutter speed
3. Check ISO and increase if needed - high ISO if moving object (not rly very important in CSI)

Question 22

What is white balance correction?

Answer 22

AWB - Automatic - camera finds brightest parts of image and assumes its ‘white - remaining colours are adapted to ‘fit’ this assumption
- indoor settings -> typically is ‘warmer’ shades so if set, camera will make the other colours ‘colder’ shades (blue)
- outdoor settings -> typically is ‘cooler’ so if set, camera makes the other colours ‘warmer’ shade (yellow)

Question 23

What do you do if there’s not enough light?

Answer 23

Flash:
- typically not the in built flash fill
- ‘bounce’ directional flashgun
- remember exposure/ISO

External light sources:
- Tungsten (back to ‘tye’ of lighting) lighting -> ‘warmer’ shade
- Be aware of glare, shadows, distortion (perception of depth)

Question 24

What is aperture?

Answer 24

Controls amount of light and depth of field.
- marked in f-stops from f22 to f1.4
- e.g. 22,16,11,8,5.6,4,2.8,1.7
- for a 50mm lens set at f2 - diameter of aperture is 50/2 = 25mm
- F22 makes the irish close down to a small aperture, f1.4 makes aperture wide open
- at f1.4 - more light gets in so the time needed to get a correct exposure is reduced

Question 25

What is shutter speed?

Answer 25

- typically from 1/2000 sec to 1 sec + B (bulb) - 100,500,250,125,60,30,15,8,4,2,1,B - B means that the shutter is open as long as the shutter button is held down -> for long exposures - When handholding, never use a shutter speed greater or less than 1/focal length of lens - e.g. if using a 50mm lens, don't use anything less than 1/60s or else you get 'camera shake'

Question 26

What ISO and shutter speed should you use for each aperture measurement?

Answer 26

f1.4 - 1/1000 - ISO 50 f2 - 1/500 - ISO 100 f2.8 - 1/250 - ISO 200 f4 - 1/125 - ISO 400 f5.6 - 1/60 - ISO 800 f8 - 1/30 - ISO 1600 f11 - 1/15 - ISO 3200 f16 - 1/8 - ISO 6400 f22 - 1/4 - ISO 12800 f32 - 1/2 - ISO 25600

Question 27

What's the rule of thumb for shutter and aperture?

Answer 27

- combination of shutter speed and aperture is to allow the light through - fast shutter speed combined with wide aperture - if slow shutter speed with wide aperture - too much light will pass through ~(over exposure) - if camera settings indicate a particular combination of shutter speed and aperture then moving each control in opposite directions by the same increment will not affect the exposure - 1/60 at f8 will be the same as 1/30 at f11 or 1/125 at f5.6

Question 28

How do you use other functions to ensure integrity?

Answer 28

Hash value/function - assigns a number to the image based on pixelation -> mathematical algorithms - message-direct - secure hash - RIPEMD-160 -> another more complex message digest algorithm Any alteration to the image affects this number therefore easily identifiable as altered images.

Question 29

What are watermarks?

Answer 29

Ususally for IP rights, unique digital watermarks is randomly 'embedded' into the image (insignificant change to the pixel value) - if image is altered, watermark is altered - can be argued that its pressure renders the image as not being authentic due to the alteration of pixels

Question 30

What's encryption?

Answer 30

An encoded digital signature is applied to the original image and when transmitted a decryption code at the reciever and verifies the authenticity of the image. - excellent secure transmission for remote transfer but if either code becomes corrupted renders the images unreadable

Question 31

What is the current guidelines for photographing a scene?

Answer 31

ACPO - 3 shot rule 1. Close up - taken to show the exhibit itself. This photograph should fill the whole picture frame and include a measurement scale 2. Intermediate - taken to clearly show the exhibit and anything immediately around it 3. Distance - taken to enable the viewer to locate the area where the exhibit is in relation to the general surroundings

Question 32

What are scene examination forms used for?

Answer 32

- To locate, record and recover all potential evidence realting to an investigation - This form is an all encompassing one that has been written for academic purposes - in reality how it would look woud depend on the type of the scene