Forensic Archiving I. [1] [1] American Heritage College Dictionary Third Edition, Houghton Mifflin Company, 1993. [2] [2] 2542,t=active+archiving&i=37447,00.asp#.

Forensic Archiving I

[1] American Heritage College Dictionary Third Edition, Houghton Mifflin Company, 1993. [2] http://www.pcmag.com/encyclopedia_term/0,2542,t=active+archiving&i=37447,00.asp#. Accessed 3/20/2009.

Forensic Archiving Documentation:

A current standard no longer reflects current practice

Times change as does a profession’s lexicon

Archiving:Preserving the scene’s recordEncompasses more than simply photography,

sketching, or imagingModern relationship with a digital world

Archiving Essentials Critical responsibility of the crime scene unit

Preserve the scene as found Impossible to predict when another pair of eyes will need to review the

“original” scene

No single archiving method is sufficient Taking notes Videography Photography Sketches 3D archiving systems CAD Writing reports

Each method has attributes and deficiencies

Crime Scene Archive Traditionally stored in

filing cabinet or storage boxes

Contemporary investigations employ a form of digital media Computer hard drive

or a CD backup

Forensic PhotographyAn Essential Skill

Telling The Scene’s Story

The Purpose of Forensic Photography

To archive the scene

Record as found

Show the relative position of evidence

Establish the relative dimensions of evidence

Complement other archiving techniques

Active vs. Passive Archiving

Active archiving: Process of combining the “rote,” the passive aspect of archiving, with an engaged brain

Thinking critically about relationship of evidence to the scene

Passive Archiving: Overview photographs and snapping photographs without considering what is being captured

Need to think about Forensic perspective or how different items at the

scene relate to each other

Photography: Is Integral Part of Scene

Search Photography is an integral part of searching the scene

Visible investigation Active investigation

Not artistic photograph but forensic photograph The artist is trying to be creative

Artist allows the landscape to guide the artistic process

Forensic investigations capture the best perspectives in order to capture the scene’s story Forensic photographer allows the scene to guide the continuum of

photographs from relevant evidence to relevant evidence

Paradoxically: forensic photographer must capture EVERYTHING

Single Lens Reflex (SLR) Cameras

Why SLR’s?Lenses can be changed

The investigator sees exactly what the lens “sees” Unless camera is modified for IR photography

Large image sensors

Near-zero lag time

Managing Your CameraCamera Function

Result

Aperture Priority You set the aperture (f/stop) and the camera sets the shutter speed

Shutter Priority You set the shutter speed and the camera sets the aperture

Manual Priority You set the aperture and the shutter speed

http://www.mir.com.my/rb/photography/fototech/apershutter/aperture.htm

Managing Your Camera Exposure control ring –

various setting may be represented by a few symbols/letters "P" is for programmed AE ”S" is for shutter priority “A” is for aperture

priority “M” refers to manual

mode

Newer autofocus SLR cameras set aperture via the lens aperture ring Instead of the thumb wheel

Shutter Speed (B)

Aperture (A)

[1] Kelby, Scott – Chapter 1 – Pro Tips for Getting Really Sharp Photos. In The Digital Photography Book, Volume 1. Peachpit Press 2006, page 1.

Focus If not in focus, the rest doesn’t matter

Tack sharp or photographs in sharp focus

Digital Cameras: The LCD viewer allows for immediate inspection of

focus CAVEAT: LCD screen is small

Use the LCD as a guide of focus

Focus (2) Use tripod with a ballhead or at least a monopod

There are situations when hand-held is the only way to get the correct photograph

Pressing shutter moves the camera Cable release option Self timer function Infrared wireless remote Anti shake mechanisms

Vibration Reduction (Nikon) Image Stabilization (Canon)

Lock the camera’s mirror in the up position Move the mirror up manually

Exposure Delay Mode (Nikon) Mirror Lockup (Canon)

Focus (3)Lens’ sharpest aperture = about two full stops

smaller than wide open If the lens is f/2.8, the best apertures would be

f/5.6 and f/8 (two full stops down from 2.8)

Avoid high ISO’s On a tripod in dim light

Do not increase the ISO Keep the ISO at the lowest possible setting

Focus SummaryLCD on the camera back unreliable gauge

of focus

Out-of-camera image manipulation

Use a tripod when possible Hand-holding the camera increases the

likelihood of obtaining out-of-focus photographsUse the camera’s burst function Brace the camera against something sturdy

Avoid high ISOs

Photographic BasicsThe Essential Terms & Considerations

Aperture ShutterISO

Light Focal LengthDepth of FieldWhite Balance

ExposureImportant

Considerations

Understating Exposure

Exposure: Amount of light entering the camera

“the duration and amount of

light needed to create an image”

Stop: The basic unit of exposure One stop is the equivalent of doubling or halving

the amount of light entering the camera

Controlling exposure allows the photographer to obtain that perfect forensic perspective

http://www.cambridgeincolour.com/tutorials/camera-exposure.htm

Understating Exposure (2)

Correct exposure is a lot like collecting rain in a bucket

While the rate of rainfall is uncontrollable Three factors remain under your control:

The bucket's width

The duration you leave it in the rain

Quantity of rain you want to collect

You just need to ensure you don't collect too little ("underexposed"), or that you don't collect too much ("overexposed”)

There are many different combinations of width, time and quantity that will achieve this For example, for the same quantity of water, you can get away with less time in

the rain if you pick a bucket that's really wide

ApertureThe First & Most Critical Decision

About Exposure Begins with Aperture

http://en.wikipedia.org/wiki/Aperture

Aperture Aperture: Size of the hole through which light enters the

camera Covered by a mechanical shutter

Limits the time the digital sensor is exposed to the light

Terminology is f-stops or f/numbers Confusing and counterintuitive – a the larger the f/number,

say f/22, the smaller the hole and visa versa

Wide Aperture f/stop or aperture of f/2.8 is wide – hole is larger

Narrow Aperture f/stop of f/22 is a narrow opening – hole is small

f/4

f/11

f/8

f/5.6

DiaphragmLens opening

Stop Down1 Full Stop

½ Light

2x Light

Aperture - Basics

Telling the Scene’s Story

The Importance of Aperture

Aperture is one of the big three players in solving the correct forensic exposure puzzle

Aperture should be FIRST setting adjusted Aperture allows scene to tell its story

Each photograph has a specific forensic perspective the photographer must capture o What at the scene and what in this photograph should

be in focus? o What needs to be captured for the scene to tell its story

Depth of Field: What is in focus

Depth of FieldWhat is in Focus

Depth of Field (DOF)Depth of Field: The concept of what is

in focus in a photograph Photographer must consider the DOF because

it tells the scene’s story

Aperture & DOF are intimately associated Size of opening on camera controls what at

the scene is in focus in a photograph

Depth of Field Establishing (Overview) Shots

For maximum depth of field Focus about 1/3 of the distance into the scene

Doo

r

Knife

5ft

15ft28ft

Where to Focus at the Scene

Small focal length wide-angle lens …… 24mmFocus @ 10’ – just in front of the body

Strive for: Maximum depth of field1. Shorten focal length2. Smaller aperture opening (larger f/number)3. Greater distance to point of focus (evidence)

Window15ft

BloodPool

Shutter SpeedHow Long is the Exposure

Shutter Speed Shutter Speed: The speed the shutter closes

Closes the aperture Controls amount of light entering camera Regardless of size of the opening, if the digital sensor is

exposed too long, the resulting photograph will be over exposed and will not meet forensic or artistic standards

Typical Shutter Speeds

Typical shutter speeds

Older cameras: shutter speeds set to halve or

double light allowed in 1/500, 1/250, 1/125, 1/60, 1/30,

1/15, etc

Newer cameras 1/3rd steps

1/500, 1/400, 1/320, 1/250, 1/200, 1/160, 1/124, 1/100, 1/80, 1/60, etc

http://photographylife.com/what-is-shutter-speed-in-photography

SUGGESTED SHUTTER SPEEDS

TO FREEZE ACTION TO CAPTURE MOTION

Children – 1/250 – 1/1000 seconds

Amusement park rides: +/- one second

Moving water/waterfalls: 1/1000 seconds or more

Moving water/waterfalls: 4 or more seconds

Sporting event: 1/500 – 1/2000 seconds

Fireworks: 1/2 – 4 seconds

Birds in flight: 1/1000th a second and above

Moving cars at night: 8-10 seconds

Night photography – one or more seconds

When taking a photo of a moving subject, changing the shutter speed can change the look of an image.

A slow shutter speed captures movement. Fast shutter speed freezes action.

Shutter Speeds & a Variety of Subjects

ObjectPhoto’d

55-200mm18-55mm

12-24mm

Focal Length

Focal Length: The distance (mm) from the center of the lens to where the image comes into critical view

Distance from Object Photographed

Equivalent ExposuresEquivalent Exposures: Different camera settings that

allow the SAME amount of light to enter the camera Resulting photographs are subtly different

Examples of equivalent exposures f/8 – f-stop and ¼ second shutter speed f/11 – f-stop and ½ second shutter speed f/16 – f-stop and 1 second shutter speed

Aperture & Shutter SpeedEquivalent Exposures

http://irinaovery.com/wp-content/uploads/2012/03/2124175721_591714ec93.jpg

The combination f/2.8 and shutter speed 1/125 sec gives a cell with number 10. 

If you do two stops on the right and towards the top of the chart, you will get the number 10 again.

80-400mm zoom lens @ 400mmf/32, 1/30sec

80-400mm zoom lens @ 400mmf/5.6, 1/1000sec

f/4, 1/500sec f/5.6, 1/250 sec

f/22, 1/15 sec

35-70mm zoom lens @ 35mm

Equivalent Exposures

f/4 – 800th sec – ISO 1250 f/5.6-500th sec - Iso1250

f/11 – 125th sec – ISO 1250 f/20 – 40th sec – ISO 1250

ISODigital Processor Sensitivity

International Organization of Standards

ISO ISO Rating: Measure of

the digital sensor’s sensitivity to light The higher the ISO

number, the more sensitive the sensor is to light

ISO settings affect exposure Change in ISO from 100 to

200 effectively doubles the light One full stop More light is not entering the

camera

ISO 100 ISO 3200

http://www.digital-photography-school.com/iso-settings

ISO Considerations Auto ISO Mode: The camera selects the appropriate ISO setting

depending upon the conditions It will try to keep the ISO as low as possible

Manual ISO Mode: Manually adjusting the ISO based on your aperture, shutter speed and conditions of the scene Overriding the camera impacts the aperture and shutter speed

If you bumped your ISO up from 100 to 400, you can shoot at higher shutter speeds and/or smaller apertures

Choosing the Correct ISO setting Light – Is the subject well lit? Grain – Do I want a grainy shot or one without noise? Tripod – Am I using a tripod? Moving Subject – Is my subject moving or stationary?

Always try to choose the lowest ISO setting possible If there is plenty of light AND need no grain in photo AND using a tripod AND

subject is stationary Use pretty low ISO rating If it’s dark AND want grain AND don’t have tripod AND subject is moving

Consider increasing the ISO - Can shoot with a faster shutter speed and still expose the shot well Trade off of increase in ISO is noisier (grainer) shots

When to use Higher ISO Settings

Indoor Sports Events – where your subject is moving fast yet you may have limited light available

Concerts – also low in light and often ‘no-flash’ zones

Art Galleries, Churches etc- many galleries have rules against using a flash and of course being indoors are not well lit

Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene

Read more: http://www.digital-photography-school.com/iso-settings#ixzz1TKC5Zi00

http://www.digicamhelp.com/camera-features/advanced-settings/iso/

ISOBy the Numbers

AUTO ISO – digital camera automatically sets the ISO speed according the the brightness of the scene, increasing or decreasing the sensitivity. User has no control over which ISO number is used

ISO 80 – for taking photos in bright light; excellent for close-ups, landscape, and portraits. Produces fine detail and image quality

ISO 100 – for extra sensitivity with little, if any, reduced image quality

ISO 200 – cloudy and overcast days. Acceptable image quality, with some visible noise

ISO 400 – suitable for indoor photography whether or not a flash is used. Useful for “stop-action” and sports photographs. Most compact digital cameras produce high to very high image noise

ISO 800, 1600 and above – useful for taking photos in very low light, or outside in good light when increased shutter speeds are required. Results can be disappointing when shooting at these high numbers with compact digital cameras, so take test photos before photographing an important event

MeteringMeasuring Light

MeteringMetering: The actual light reflected

from an object being photographed• Cameras need to know how much light is

entering the cameraThus allowing the camera to choose a

starting point for an appropriate exposure

Modern digital cameras use TTL (through-the-lens) metering systems Cameras measure the amount of light reflected

from object to the digital sensor

Illumination Incident light: The actual light hitting the object

This is what should be measure Not reflected light

TTL system measures reflected light Approximation of the incident light, which is why cameras

don’t always get it right May force the camera into taking under or over exposed

photographs Backlit situation

Older cameras did not have built-in metering systems Photographer had to use hand-held meter to measure the

incident light hitting the object

ObjectPhotographed

External Meter Light Source

Incident Light

Reflected Light

TTL: Through-the-lensIn-Camera Metering

If all objects reflected the same percentage of incident light, the TTL would work just fine Real-world subjects vary greatly in their reflectance. 

In-camera metering is standardized based on the light reflected from an object appearing as middle gray  If object is lighter or darker than middle gray

In-camera light meter will incorrectly calculate the amount of light The result is an under or over-exposed photograph

Hand-held light meter calculates the same exposure for any object under the same incident lighting

Canon PowerShot Metering Modes :

Evaluative, Center Weighted Average, Spot

LensesTelephoto

Capture images at long distances Long-range photography

of objects

Wide angle• Capture panorama

Establishing photography

Macro – Close-up lenses Allow close photography

Detailed evidence photography

Lenses Focus Light

http://en.wikipedia.org/wiki/Lens_%28optics%29

White Balance

White BalanceWhat is White

Color TemperatureDegrees Kelvin

1800 4000 5500 8000 12,000 16,000

Visible Color Red Yellow White Light Blue

Blue Dk. Blue

WB – set on “auto” WB – set on “fluorescent”

PhiladelphiaFlower Show

[1] Lezano, ibid, page 42.

White Balance (WB) White Balance: How the camera “interprets” white

Allows camera to produce accurate colors under a variety of lighting conditions

The camera relies on the photographer to tell it what the lighting condition is via the white balance setting

White balance can only be corrected using software Photograph must be taken in RAW format

Poor white balance signifies sloppy work Someone simply going through the motions of taking pictures

without paying attention to the business of forensic photography

Little or no thought about the consequences of selecting – or not selecting – the proper WB

Camera Option DescriptionAuto The camera sets the white balance.Incandescent The choice when the majority of the

lighting comes from incandescent light (common light bulbs)

Fluorescent The choice when the majority of the light comes from fluorescent lights.

Direct Sunlight The choice for subjects lit by sunlightFlash The choice when using the built-in flash –

mimics daylight.Cloudy The choice in daylight when the sky is

overcastShade The choice in daylight for subjects in the

shadeCustom Use a gray or white object at the scene as a

reference for the camera the WB

Camera White Balance Options

18% Gray card

Place gray card in scene oriented toward the direction of the incident light.

Take reading from it using a reflected light meter.

Assures photographer of consistent exposures across their photographs.

This technique is similar to using an incident meter, as it depends on the illuminance but not the reflectivity of the subject.

A gray card is only useful for setting or correcting the balance of neutral colors.

Use photograph of a Color Checker as a reference for color balance adjustments.

Gray & Color Checker Cards

FlashDrawback

Creates harsh light Washes out evidentiary

detail

Critical Uses Can Eliminate shadows Can Minimize glare Bounce light to provide

softer illumination

Flash BasicsFlash illumination is

dramatically affected by distance The inverse square law

The difference between a light at 2.8 feet & the same light at 4 feet is 1 stop

Same for 8 feet to 11 feet.

Same for 16 feet to 22 feet

http://photography-on-the.net/forum/showthread.php?t=171657

Cup @ 2.8 feet is 1 Stop Brighter than cup @ 4.0 feet

Takes 16x as much light to illuminateCup @ 11 Feet to = cup @ 2.8 feet

A Roadmap The Perfect Forensic Photograph

Set WB

CheckExposure

Set Shutter

BracketShots

Check WB & DOFOn Photo

Take PhotoSet Aperture

Readjust WB – DOF

Set CameraTo Manual

Close up EstablishingDOF

Choose Perspective

Observe &Smile

White Balance Light

General Illumination Glare

Forensic Perspective Relationship to other Evidence

Deceased? Weapons? Trail direction?

Name The Three Problems…