Forensic Archiving I

Forensic Archiving Refers to preserving scene’s record. A departure from usual

terminology

Encompasses more than simply photography, sketching, or imaging.Has modern relationship with a digital world.

Photography, is a sub-category under the umbrella of the broader and more relevant term, forensic archiving.

Term: Documentation:A Current standard no longer reflects current practice. Times change as does a profession’s lexicon.

[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.

Critical responsibility of crime scene investigative unit, Preserve the scene as found, so that anyone can “see” what original

investigators saw. The essence of the scene is critical … impossible to predict when

another pair of eyes will need to review the “original.”

No single archiving method is sufficient, Taking notes, Writing reports Increasingly complex technology.

Video alone is insufficient and inadequate as are the newer 3D archiving systems, though they are certainly capable of providing more accurate measurements.

Each method has attributes and deficiencies

A complete and competent archive of the scene requires a battery of techniques.

Archiving Essentials

Forensic PhotographyAn Essential Skill

Telling The Scene’s Story

The Purpose of Forensic Photography

Why Photograph the Scene?

“To archive the scene.” An activity with far reaching implications. The most obvious are straight forward.

Record and preserve the as-found condition of the sceneShow the relative position of evidence at the sceneEstablish the relative dimensions of evidenceComplement 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 of a room of a dead body, moving from different areas and snapping photographs without considering what is being captured.

Photography: Is Integral Part of Scene Search

Part of visible investigation … search of scene. An essential part of an active investigation. Recreational and forensic photography part ways.

The artist is trying to be creative in order to capture the scene from an artistic sense.

Forensic investigations are not artistically creative, but creative in the sense that the photographs capture the best perspectives in order to capture the scene’s story.

Artist allows the landscape to guide the artistic process,

Forensic photographer allows the scene to guide the continuum of photographs in the same way: from relevant evidence to relevant evidence.

Paradoxically: forensic photographer must capture EVERYTHING.

Single Lens Reflex Cameras - SLR

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

Newer autofocus SLR cameras set aperture via the lens aperture ring; instead - aperture is controlled by the thumb wheel for BOTH shutter Speed (B) and Aperture (A).

A method first pioneered by Canon on their manual focus Camera, the Canon T90 back in 1986.

The VISIBLE confirmation of the selected aperture used on camera like this type is via the LCD on the top panel OR through the viewfinder.

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

An exposure control ring found in many modern SLR. The various setting may be represented by a few symbols/letters, "P" is for "Programmed AE", the "Tv" is for shutter priority while the Av (aperture value) is referring to aperture priority - Canon's way of interpreting in their A and T series camera bodies.

Why SLR’s?Lenses can be changed in order to meet

specific photographic challengesThe investigator sees exactly what the lens

“sees.” Unless camera is modified for IR photography.

Digital SLRs have large image sensors that produce high-quality photos.

An SLR has a near-zero lag time.

Essential Skills of Forensic Photography

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

Digital Cameras: The LCD viewer allows for immediate inspection of focus.

CAVEAT: LCD …Small image …out-of-focus photographs appear in focus, but out of focus when viewed on on the computer screen.

Use the LCD as a guide of focus

Concept: Tack Sharp: Photographs in sharp focus

Blurry photographs are of little use and serve no investigative purpose.

[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 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. Use cable release, self timer function infrared wireless remote .

Lock the camera’s mirror in the up position. Camera moves the mirror up and locks it while taking the photograph

which causes movement. Move the mirror up manually Exposure Delay Mode (Nikon) or Mirror

Lockup (Canon) . Vibration Reduction (VR) (Nikon) or Image Stabilization (IS)

(Canon) minimize vibration from pressing the shutter. Rules of thumb:

1. If you are hand-holding the camera, activate the VR system, and 2. If the camera is on a tripod, inactivate the VR system.

Shoot at the 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).

Each lens has a sweet spot that delivers its sharpest images.

High quality lenses make a difference. Use high quality “glass” for tack sharp photographs.

Avoid high ISO’s if possible.

On a tripod in dim light … do not increase the ISO. Keep the ISO at the lowest possible setting.

Resulting photographs will be sharper. If hand holding in dim light, may be impossible to get the photograph without using a higher ISO. .

Focus

Photographic BasicsThe Essential Terms - & Considerations

Aperture ShutterISO

Light Focal LengthDepth of FieldWhite Balance

ExposureImportant

Considerations

Exposure: Amount of light entering the camera. It has been defined as,

“the duration and amount of light needed to create an image.”

Stop: The basic unit of exposure … where 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, the one

Definitions:

Exposure: Tells the best forensic story. Only then does the photograph have the correct forensic exposure.

Correct forensic exposure controls light entering the camera so that the scene can tell its “story.”

Exposure

ApertureThe First & Most Critical Decision

About Exposure Begins with Aperture

Size of the hole through which light enters the camera. Covered by a mechanical shutter that closes more quickly or more slowly

(shutter speed) Limits the time the digital sensor is exposed to the light.

Camera settings used to adjust the size of the hole Terminology is f-stops or f/numbers.

Confusing and counterintuitive because the larger the f/number, say f/11 or f/22, the smaller the hole and visa versa.

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

Narrowf/stop of f/22 is a narrow opening – hole is smaller.

Aperture

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

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 of photographer based on the photographer’s assessment of the appropriater perspective needed 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

It is the first camera setting that controls the most important perspective of the crime scene: What is in focus.

By choosing the aperture setting first, not just determining what is in focus at the scene, but is making that decision after critically evaluating the scene.

Determining the correct perspective.

Aperture: Forensic Equivalent of Archiving Gold.

Depth of FieldWhat is in Focus

Determined by the Aperture Setting

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

Depth of Field - Rule of Thumb Establishing (Overview) Shots

For Maximum Depth of FieldFocus about 1/3 of the Distance into the Scene

DOF: One third in frontThree quarters beyond

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.

The shutter is the door to the outside world that remains open for fixed periods of time measured in seconds.

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

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

Role of the shutter is to control light getting to digital sensor, by opening and closing the cover over the aperture.

ObjectPhoto’d

55-200mm18-55mm

12-24mm

Focal Length

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

Distance from Object Photographed

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.

Suggested Shutter Speeds for Photographing Variety of Subjects

ISOThird Leg of the Exposure Puzzle

Digital Processor SensitivityInternational Organization of Standards

ISO Rating: Third leg of the exposure puzzle

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 available to the photograph … a full stop.

More light is not entering the cameraDigital sensor is more sensitive to light, which in

essence changes the sensitivity of the camera a full stop.

ISO

ISO 100 ISO 3200

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

Most people keep digital cameras in ‘Auto Mode’ where the camera selects the appropriate ISO setting depending upon the conditions you’re shooting in (it will try to keep the ISO as low as possible)

Overriding the camera impacts the aperture and shutter speed needed for a well exposed shot. For example – 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?

If plenty of light - AND need no grain in photo – AND using a tripod - AND subject is stationary. Use pretty low ISO rating. ject

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.

ISO Considerations

Situations For 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

MeteringMeasuring Light

Metering/Illumination

Cameras need to know how much light is entering the camera, Actual light reflected from an object being photographed.

Cameras measure the light in order to choose starting point for 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.

The light that should be measured is actual light hitting the object – Incident light. TTL system measures reflected light

Approximation of the incident light, which is why cameras don’t always get it right.

Sometimes TTL system forces the camera into taking under or over exposed photographs. Backlit situation

Older cameras did not have built-in metering systems, forced the photographer to use hand-held meter to measure

the incident light hitting the object.

Illumination

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: Standardized based on the light reflected from an object appearing as middle gray.  Camera aimed directly object 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.

ObjectPhotographed

External Meter Light Source

Incident Light

Reflected Light

TTL: Through-the-lensIn-Camera Metering

Canon PowerShot Metering Modes :

Evaluative, Center Weighted Average, Spot

Lenses

Telephoto Capture images at long

distancesLong-range photography

of objectsWide 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 BalanceWhat is White

Color TemperatureDegrees Kelvin

1800 4000 5500 8000 12,000 16,000

Visible Color Red Yellow White Light Blue

Blue Dk. Blue

White Balance (WB) Tells camera how to “interpret” white.

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

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.

[1] Lezano, ibid, page 42.

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 Options for White Balance

What Are The Three Problems With This Scene Photograph?

White Balance Light

General Illumination Glare

Forensic Perspective Relationship to other Evidence

Deceased? Weapons? Trail direction?

FlashDrawback

Creates harsh lightWashes out evidentiary

detailCritical Uses

Can Eliminate shadowsCan Minimize glareBounce 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

Set WB

CheckExposure

Set Shutter

BracketShots

Check WB & DOFOn Photo

Take PhotoSet Aperture

Readjust WB – DOF

Set CameraTo Manual

The Perfect Forensic PhotographA Roadmap

Close up EstablishingDOF

Choose Perspective

Observe &Smile