Photography - Getting Started

Question 1

What is SWGIT?

Answer 1

Scientific Working Group on Imaging Technology

Question 2

What is the goal of SWGIT

Answer 2

Ensure the successful introduction of forensic images in a court of law

Question 3

Give examples of unacceptable means of introducing photographs in court.

Answer 3

Cell phone images
Special effects
Filters

Question 4

State SWGIT s. 1.4

Answer 4

Digital imaging is an accepted practice in forensic science, law enforcement and the courts.

Question 5

State SWGIT s, 2.1

Answer 5

Image capture devices should be capable of rendering an accurate representation. Different applications will dictate different standards of accuracy,

Question 6

According to SWGIT, what must a digital camera be capable of doing?

Answer 6

Interchangeable lenses
Manual override for exposure and focus
Off-camera flash
Remote shutter release
Tripod mount

Question 7

List the two main types of interchangeable lenses discussed in class.

Answer 7

zoom lenses
Fixed/primary lenses

Question 8

What are zoom lenses?

Answer 8

Lenses with variable focal lengths.

Question 9

What is a specific type of zoom lens discussed in class?

Answer 9

Telephoto lens

Question 10

What are telephoto lenses?

Answer 10

Lenses with variable focal lengths used for photographing very distinct subjects (wildlife or sports)

Question 11

What were the two types of fixed/primary lenses discussed in class?

Answer 11

Macro lenses
Wide angle lenses

Question 12

What is a macro lens?

Answer 12

Captures small subjects very close, 1:1 ratio

Question 13

What is a wide angle lens?

Answer 13

Used when you want to capture as much as possible (landcapes, cityscapes, architecture)

Question 14

What focal length is the most accurate representation of the human eye?

Answer 14

50 mm

Question 15

What type of lens is used for impression shots?

Answer 15

Macro lenses

Question 16

Why are wide angle lenses not typically used in forensics?

Answer 16

Distort the images

Question 17

What are the possible sets of focal lengths for zoom lenses?

Answer 17

24-70 mm
18-55 mm

Question 18

What are the possible focal lengths of macro lenses?

Answer 18

60 mm
105 mm

Question 19

What is the focal length range of telephoto lenses?

Answer 19

70-300 mm

Question 20

What is the focal length of a wide angle lens?

Answer 20

20 mm

Question 21

What is a remote shutter release?

Answer 21

Communicates with camera via radio waves
Allows for one to take a photo without physically having to press the shutter release button

Question 22

In what type of scene should a tripod always be used and why?

Answer 22

Night scenes; shutter open for longer periods of time

Question 23

State section 2.2 of SWGIT

Answer 23

Image compression is the process of reducing digital file size. Compression may be lossy or lossless. The decision to use lossy or lossless compression will be dictated by the intended use of the image

Question 24

What are the 3 digital file types discussed in class?

Answer 24

JPEG
TIFF
RAW

Question 25

What does JPEG stand for?

Answer 25

Joint photographic experts group

Question 26

What does TIFF stand for?

Answer 26

Tagged information file format

Question 27

What is RAW

Answer 27

Unprocessed data. Contains all of the image information captured from the camera's sensor

Question 28

What does it mean if a compression format is lossy?

Answer 28

Information is lost permanently

Question 29

Is JPEG a lossy or lossless compression format?

Answer 29

Lossy

Question 30

How does JPEG decide what to keep in an image?

Answer 30

The computer will look at the file and decide what can be discarded based on an algorithm involving neighbouring pixels (inerpolation). Only tosses information that can be replaced. Removes colour pixels and adds unwanted artefacts

Question 31

What are the pros of JPEG? (5)

Answer 31

Maximum number on card Fastest in-camera processing Compatible with all types of computer operating systems Small file size = easy to transfer and send across platforms

Question 32

What are the cons of JPEG? (5)

Answer 32

8bit image Limited colour gamut possibly leading to low resolution Lossy format Higher level of compression = greater data loss Every time an image is modified and resaved, it goes through a compression and loses more data.

Question 33

List the 4 pros of TIFF.

Answer 33

High quality (16bit) Does not require post processing Lossless format Images can be enhanced and resaved without comrpression

Question 34

List the 3 cons of TIFF.

Answer 34

Large files created resulting in slow in-camera processing Requires large memory cards to store images Files will take up large amount of space on computer storage

Question 35

List the pros of RAW. (3)

Answer 35

All original detail stays with the image 12bit image Camera performs no brightness/contrast adjustments, colour balancing or sharpness

Question 36

List the cons of RAW. (4)

Answer 36

No industry standard for RAW format thus each manufacturer has its own proprietary format Not compatible with mainstream computers thus images will need to be converted to JPEG or TIFF first Requires special programs for viewing Requires post-processing

Question 37

How much more data does 16 bit contain compared to 8 bit?

Answer 37

17 million times more data

Question 38

What is BIT depth?

Answer 38

Number of tones between pure black and pure white

Question 39

What is the bit depth of JPEG 8 bit?

Answer 39

2^8 = 256

Question 40

What does BIT depth represent?

Answer 40

Each channel and all the different colour combinations

Question 41

What file format does STPS use and why?

Answer 41

JPEG and RAW JPEG for court purposes RAW for analysis/comparison purposes