merging digital photography with crime scene investigations

1

Merging Digital PhotographyMerging Digital PhotographyWith Crime Scene InvestigationsWith Crime Scene Investigations

LVMPD Criminalistics Bureau

2

IntroductionIntroduction This training is designed to develop a foundation for the

basics of digital photography, and the integration of digital photography into a law enforcement environment.

Students will leave this training with: 1) A fundamental understanding of how digital

imaging works. 2) The ability to operate, and maintain a 35mm digital

camera. 3) An understanding of policies and procedures related to the capture, transfer, storage, and output of digital images to keep the evidentiary integrity of images intact.

3

A “Mega-A “Mega-ByteByte” of ” of Digital History…Digital History…

4

The first video tape recorder captured live images from television cameras by converting the information to electrical impulses (digital) and saving the information to magnetic tape.

1951

5

19641964First electronic photos of Mars. NASA, at the Jet

Propulsion Lab in Pasadena, CA, received electronic signals from video cameras on board the Mariner (IV) spacecraft on its way to Mars. Although no CCD was used, much of the same technology was utilized in the development of the modern day CCD.

6

Bell Labs constructed the world’s first solid-state video camera using a CCD as the imaging device. This digital technology was applied to still cameras several years later.

CCD Wafer Complete CCD Assembly

1970

7

THE FIRST EMAIL was sent. The person responsible

for this was Ray Tomlinson, a computer engineer. Tomlinson was employed by Bolt Beranek and Newman, a company contracted by the US Defense Department to build ARPANET, the precursor to the internet.

1971

8

In 1972, Texas Instruments patented a film-less electronic camera, the first company to do so.

1972

9

The first astronomical image (100x100 pixels) was captured on CCD through an 8 inch telescope.

1974

10

19751975Kodak prototype still camera was designed with

the world’s first known operational electronic CCD. The sensor captured a 100x100 pixel image and it required 23 seconds to record a single image onto a cassette tape

11

Sony released the Sony Mavica electronic still camera. This was the first commercial electronic still camera on the consumer market. Images were recorded onto a mini disc and then put into a video reader that was connected to a television monitor or color printer.

1981

12

19841984Canon conducted a trial of a professional

color still camera (RC-701) and an analog transmitter at the LA Olympics. Images were transmitted back to Japan via phone lines. The camera used a 400 pixel CCD.

13

19851985The Nikon SVC (Still Video Camera) prototype

camera was unveiled. It had a 2/3 inch CCD of 300,000 pixels. It allowed the analog recording of 25 or 50 images on a small floppy disc of 2 inches.

14

Work was started to establish a standard method for representing photographic images in digital form. The group formed was ultimately called “Joint Photographic Experts Group” under the auspices of the International Organization for Standards (ISO), and the result is known as (JPEG).

1986

15

The worlds first completely digital consumer camera was unveiled, the Dycam Model 1. It stored 32 images internally on 1MB RAM and only shot B/W.

1990

16

In 1992 the Kodak DCS 200 was released. This camera was the first with a built in hard drive for image recording and was a 1.5 Megapixel camera. You could own this beauty for a mere $25,000.00.

1992

17

19941994

Compact flash memory card first available on the market. It was introduced by SanDisk Corp. The first discs held 2-24 MB of data. It was the first solid state memory card designed that could retain data indefinitely without the use of a battery.

18

……And On And On…And On And On…

19

Why Digital For Law Why Digital For Law Enforcement?Enforcement?

Why Digital For Law Why Digital For Law Enforcement?Enforcement?

20

With current technology, images are as good or better an traditional 35mm film.

21

With current technology, images are as good or better than traditional 35mm film.

Images can be reviewed instantaneously at a scene for proper exposure, composition, content, etc.

22



Hundreds of images can be stored on a single memory card, eliminating the need for multiple rolls of film.

23




Images are easily shared between law enforcement personnel and agencies through electronic means.

24





Film, chemicals, and photographic paper usage is dramatically reduced.

25






Storage space is reduced to nearly nothing.

26






Storage space is reduced to nearly nothing.Images can be digitally tracked with an audit trail

to authenticate chain of evidence

27

The Courts View On The Courts View On Digital Imaging…Digital Imaging…

29

1) Got SOPs?

30

1) Got SOPs?

2) Can “Frye” Fly?

31

If you can answer these If you can answer these two questions with a two questions with a

“YES”,“YES”, chances are, you chances are, you are going to be set in are going to be set in

court.court.

32

SOPs ARE A MUST!SOPs ARE A MUST!

Standard Operating Procedures MUST be in place prior to utilizing digital imaging in the field for evidentiary purposes. The SOP should include…

When and how digital imaging is appropriate to use

Chain of CustodyImage SecurityImage Enhancement ProceduresProper Dissemination of Digital Images

33

Court PrecedenceCourt Precedence

A landmark case regarding any new technology was….

34

Frye v. United States (1923)Frye v. United States (1923)

The resulting decision from this case is as follows…

35

Frye v. United States (1923)Frye v. United States (1923)

Any technique after being invented or discovered within a particular field, would first be subject to rigorous analysis by the scientific community during its “experimental stage.” Only after this community “agreed” that the technique was valid would evidence of its use be admissible in court.

36

The IAI (International Association for Identification) reaffirms our beliefs that digital photography is a viable method of photographic documentation…

37

International Association for IdentificationResolution 97-9

“… the International Association for Identification recognizes that electronic/digital imaging is a scientifically valid and proven technology for recording, enhancing, and printing images and like conventional silver-halide base photography, it is accepted by professional commercial photographers, law enforcementphotographers, and the identification community.”

39

So…What is a Digital Photograph?So…What is a Digital Photograph?

A digital photograph is simply an image that has been created by encoding information using a binary system made up of ones and zeros, much like that of a standard computer. As a matter of fact…

40

Your Camera Your Camera ISIS A Computer A Computer

Each time you take a picture, millions of calculations have to be made in just a few seconds. It’s these calculations that make it possible for the camera to preview, capture, compress, filter, store, transfer, and display the image. All of these calculations are performed by a microprocessor in your camera that’s similar to the one on your desktop computer.

42

Instead of film, digital cameras use a solid-state device called an image sensor, otherwise known as a CCD (Charged Coupler Device). On the surface of each of these silicon chips is a grid containing millions of photo sensitive diodes called photo-elements, or PIXELS.

43

CCD’sCCD’s The area of 35mm film is 24mm x 36mm, whereas the area

of a CCD could be as much as 40% smaller. This will result in correspondingly shorter focal lengths from your lenses.

Typical sensor size of

3, 4, and 5 megapixel camera

Typical sensor size of

6 megapixel cameras

44

Images captured on a digital camera with a 1.6 magnification ratio on the CCD look like this…

100mm Lens

Film Digital

35mm Lens

45

What exactly is a pixel?What exactly is a pixel?Short for “picture –element" a pixel is the

smallest picture element of a digital image. Pixels are similar to grain in a photograph.

46

The ExposureThe ExposureThe ExposureThe ExposureWhen the shutter is released and light

hits the sensor, each pixel on the sensor records the intensity of the light that falls on it by accumulating an electrical charge. The more light that hits the pixel, the greater the electrical charge. When the shutter is closed and the exposure is complete, each pixel is measured and given a digital number.

47

Pixels do NOT record color, only brightness values. The pixels record only in gray scale, a series of 256 increasingly darker tones, ranging form pure white to pure black. The sensor reacts to the AMOUNT of light hitting it, not color of light. No color information is passed on.

48

Creating Color From Black & WhiteCreating Color From Black & White

Since daylight is made up of red, green, and blue light, placing red, green, and blue filters over individual pixels on the image sensor can create color images.

49


With filters in place, each pixel records only the brightness of the light that matches its filter when passing through it, while other colors are blocked. For example, a pixel with a red filter knows only the brightness of the red light that strikes it.

50


This step is very computer intensive since the comparisons with as many as eight neighboring pixels is required to perform this process properly.

51

Three Pillars of Digital Image QualityThree Pillars of Digital Image Quality

52


RESOLUTION

53


RESOLUTIONNOISE

54


RESOLUTIONNOISEDYNAMIC RANGE

55

What is Resolution?What is Resolution?

Resolution is the equivalent to grain in a silver based photograph. The pixel is a single point in the image that can take on any one of many millions of colors. The more pixels in any one area, the greater the resolution.

56 25 x 25 ppi

200 x 200 ppi

The greater the RESOLUTION, the greater the detail.

57

Common Image Sizes and Print Sizes at 300 dpi. Image Size Megapixels Print Size

4064 x 2704 11.1 13 x 9

3088 x 2056 6.3 10 x 7

2048 x 1536 3.0 7 x 5

1600 x 1200 2.0 5 x 4

1280 x 960 1.2 4 x 3

640 x 480 0.3 2 x 1.5

(Resolution) (In Inches)

58

What Is Noise?What Is Noise?Noise is the digital equivalent of film grain. It can look like grain though more often it looks more like ugly speckles. This results from a variety of sources, including sampling errors in pixels, temperature-induced issues within the sensor elements, etc. Noise is most evident in even areas of color such as shadows, or in the sky.

59

Just as high-speed film yields more grain than Just as high-speed film yields more grain than low-speed film, digital photos taken at high ISO low-speed film, digital photos taken at high ISO settings show much more noise than photos settings show much more noise than photos taken at low ISO settingstaken at low ISO settings

60

Noise Reduction SoftwareNoise Reduction SoftwareSoftware solutions such as “Noise Ninja” is

extremely effective in reducing apparent noise within images.

61

What Is Dynamic Range?What Is Dynamic Range?

Also known as bit depth, this is similar to exposure latitude in traditional film photography. Greater dynamic range means having a greater range of tones in an image. Selecting a camera that has good dynamic range is just as important as selecting the type of film you would use in a traditional SLR.

62

Dynamic Range ComparisonDynamic Range Comparison

Comparison Comparison

Comparison

Good Range Poor range

63

Dynamic Range ExamplesDynamic Range Examples

Good Range

Poor Range

64

Commonly Used File FormatsCommonly Used File Formats

You have a choice of many file formats to save digital images in after you download them, but there are only three formats that digital cameras use to write and store these images at the time of exposure.

JPEGTIFFRAW

65

JPEGJPEG Format Format

JPEG file format is by far the most popular format for photographic images. All digital cameras use this format to save their images in, unless you, as the photographer specify otherwise. A JPEG is a lossy (or compressed) file.

66

TIFFTIFF Format Format

TIFF (Tagged Image File Format) is probably the second most popular form of image file storage. This format stores images in an uncompressed state. Storing in this manner will increase the file size of each image, but there will be no image degradation due to compression.

67

RAWRAW Format Format

This format stores the data directly from the image sensor without first processing it. This data contains everything captured by the camera. This format also records all the color and other information that is applied during processing to enhance color accuracy and other aspects of image quality.

68

What Is Image Compression?What Is Image Compression?Image compression is accomplished by

breaking up an image into blocks of 64 pixels (8x8). Each block is then analyzed and certain pixels are thrown away. The amount of information thrown away is determined by the amount of compression applied. The image is recreated when it is de-compressed.

69

Every time a compressed (JPEG) image is opened, changed, and then closed, there will be quality loss in the image. Depending on the compression ratio and the amount of times the image is changed, the degradation may be almost unnoticeable, or quite apparent.

VERY IMPORTANT!VERY IMPORTANT!

70

JPEG CompressionJPEG CompressionBelow is a greatly enlarged image that

shows the effects of an image that has the maximum amount of compression versus minimal compression.

Minimum Compression Maximum Compression

71

Compressed ImagesCompressed ImagesA heavily compressed image will show

“blockiness” when enlarged, whereas an image with less compression retains a smooth look.

72

A single pixel saved as a JPEG A single pixel saved as a JPEG under three file compression under three file compression settings.settings.

Low Medium High

73

Las Vegas Metropolitan Police Dept.Las Vegas Metropolitan Police Dept.Criminalistics Bureau

Policies & Procedures Digital Imaging

merging digital photography with crime scene investigations

Documents