photography Flashcards
what are scene photos
- general photos taken of the scene prior to processing
- as found by the forensic unit upon arrival
- painting a picture as found
what are exhibit photos
- specific set of photos of an exhibit/ object/piece of evidence
- consists of a series of 4 photos, a defined process
- area where exhibit/ evidence should be in scene photos
do you need to be a professional photographer to be a crime scene photographer
- no
- but do need to be competent
- should have formal training (for court purposes)
- understand the criteria for photographs being admissible in court
what is the correct camera technique
- right hand hold camera body by right side/ grip
- left hand holds/ supports barrel of the lens from underneath
what should you verify before you start taking photos
- is the scene safe to photo
- what PPE precautions do you need to take
- do you have lawful authority to be there
- what type of scene is it
what do crime scene photos try to capture
- many diff directions and angles
- show layout of scene, spatial relationships between items
- capture the position of the evidence
- can document perspecctive of any known/ potential witnesses
- record the area in which the crime took place and all secondary scenes
what logical succession should photos be taken in
general to specific
photos of a street, field, house etc are an example of what
overall
what four photographs are required for a specific item
- overall
- midrange
- closeup
- closeup w scale
what is the typical camera used for CS photos
digital single lens reflex (DSLR)
what is a digital photo
- made when a light sensitive microchip (sensor) captures light on pixels
- light is recorded on each pixel as a specific electric charge which is read by the camera as image info which is stored as a file on a memory card
what does CCD stand for
charge coupled device
what is CCD
- digital equivalent of film
- contains millions of silicon photo sensors
- each photo sensor is a pixel
- image passes through lens and is focused onto CCD
what is exposure
amount of light
what is exposure controlled by
shutter speed/ aperature
what is JPEG stand for
Joint Photographic Experts Group
what is the jpeg format
- most common
- you lose some quality each time you open/ close file
what does TIFF stand for
tagged image file format
what is the TIFF format
- high quality
- large files
- lossless compression
- useful when opening/ saving file repeatedly
what is the proprietary format
RAW
describe the RAW format
- nikon has their own format, and so does cannon
- stores the highest quality image
- has been called the digital “negative”
what is exposure
the amount of light that reaches the camera sensor (CCD)
what does this describe the amount of light that reaches the camera sensor (CCD)
exposure
what does an overexposed photo look like
too much light (very light photo)
what does an underexposed photo look like
too little light (dark photo)
what are the camera ssettings that affect the exposure of an image
- aperture
- shutter speed
- camera ISO
what is the aperture
the size of the opening in the camera lens through which light passes
the bigger the opening of a camera lens, the ______
more light passes through
how is the aperture stated/ written
an f-number or f-stop
does F4 or F32 let in more light
- F4 most light
- F32 less
- think of it like a fraction (bigger F-stop means smaller fraction so less light)
when you move from one f-stop to the next, what happens
- you are either doubling or halving the amount of light that is captured
- F8 to F11 (half the light)
- F22 to F16 (double the light)
what is the shutter speed
the length of time the camera shutter stays open, exposing light onto the camera sensor
what does this define the length of time the camera shutter stays open
shutter speed
the faster the shutter speed, the _____ (shorter/longer) the time the image sensor is exposed to light
shorter
the slower the shutter speed, the _____ (shorter/longer) the image is exposed to light
longer
how is shutter speed typically noted
as fraction of a second (1/500, 1/250, 1/30 etc)
what is the longest shutter time setting on a DSLR camera
30 seconds
any time over _________ of a second for shutter speed can introduce a camera shake
1/60
what is ASA/ISO
a numerical rating that describes the sensitivity to light of CCD/film
what does this define a numerical rating that describes the sensitivity to light of CCD/film
ASA/ISO
true or false ASA/ISO affects the amount of light entering the camera
false
how does ASA/ISO affect the exposure of a photo
brightens a photo after the sensor has been exposed to light
what are the typical ranges of ASA/ISO
100-3200 (but can go higher or lower)