Photography - Getting Started Flashcards
What is SWGIT?
Scientific Working Group on Imaging Technology
What is the goal of SWGIT
Ensure the successful introduction of forensic images in a court of law
Give examples of unacceptable means of introducing photographs in court.
Cell phone images
Special effects
Filters
State SWGIT s. 1.4
Digital imaging is an accepted practice in forensic science, law enforcement and the courts.
State SWGIT s, 2.1
Image capture devices should be capable of rendering an accurate representation. Different applications will dictate different standards of accuracy,
According to SWGIT, what must a digital camera be capable of doing?
Interchangeable lenses
Manual override for exposure and focus
Off-camera flash
Remote shutter release
Tripod mount
List the two main types of interchangeable lenses discussed in class.
zoom lenses
Fixed/primary lenses
What are zoom lenses?
Lenses with variable focal lengths.
What is a specific type of zoom lens discussed in class?
Telephoto lens
What are telephoto lenses?
Lenses with variable focal lengths used for photographing very distinct subjects (wildlife or sports)
What were the two types of fixed/primary lenses discussed in class?
Macro lenses
Wide angle lenses
What is a macro lens?
Captures small subjects very close, 1:1 ratio
What is a wide angle lens?
Used when you want to capture as much as possible (landcapes, cityscapes, architecture)
What focal length is the most accurate representation of the human eye?
50 mm
What type of lens is used for impression shots?
Macro lenses
Why are wide angle lenses not typically used in forensics?
Distort the images
What are the possible sets of focal lengths for zoom lenses?
24-70 mm
18-55 mm
What are the possible focal lengths of macro lenses?
60 mm
105 mm
What is the focal length range of telephoto lenses?
70-300 mm
What is the focal length of a wide angle lens?
20 mm
What is a remote shutter release?
Communicates with camera via radio waves
Allows for one to take a photo without physically having to press the shutter release button
In what type of scene should a tripod always be used and why?
Night scenes; shutter open for longer periods of time
State section 2.2 of SWGIT
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
What are the 3 digital file types discussed in class?
JPEG
TIFF
RAW
What does JPEG stand for?
Joint photographic experts group
What does TIFF stand for?
Tagged information file format
What is RAW
Unprocessed data. Contains all of the image information captured from the camera’s sensor
What does it mean if a compression format is lossy?
Information is lost permanently
Is JPEG a lossy or lossless compression format?
Lossy
How does JPEG decide what to keep in an image?
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
What are the pros of JPEG? (5)
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
What are the cons of JPEG? (5)
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.
List the 4 pros of TIFF.
High quality (16bit)
Does not require post processing
Lossless format
Images can be enhanced and resaved without comrpression
List the 3 cons of TIFF.
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
List the pros of RAW. (3)
All original detail stays with the image
12bit image
Camera performs no brightness/contrast adjustments, colour balancing or sharpness
List the cons of RAW. (4)
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
How much more data does 16 bit contain compared to 8 bit?
17 million times more data
What is BIT depth?
Number of tones between pure black and pure white
What is the bit depth of JPEG 8 bit?
2^8 = 256
What does BIT depth represent?
Each channel and all the different colour combinations
What file format does STPS use and why?
JPEG and RAW
JPEG for court purposes
RAW for analysis/comparison purposes
