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Chapter 3
Chapter 3
History
History
History
History
History
History
History
History
History
History
History
History
Crime Scene Photography
Crime Scene Photography
Film Photography
Film Photography
Digital Photography
Digital Photography
Cameras
Cameras
Lenses
Lenses
Lenses
Lenses
Aperture and Shutter Speed
Aperture and Shutter Speed
Depth of Field
Depth of Field
DSLR Modes
DSLR Modes
Illumination
Illumination
Filters
Filters
Tripods
Tripods
Crime Scene Photography Log
Crime Scene Photography Log
Crime Scene Photography
Crime Scene Photography
Crime Scene Photography
Crime Scene Photography
Crime Scene Photography
Crime Scene Photography
Special Crime Scene Photography
Special Crime Scene Photography
Special Crime Scene Photography
Special Crime Scene Photography
Special Crime Scene Photography
Special Crime Scene Photography
Digital CS Photography
Digital CS Photography
Digital CS Photography
Digital CS Photography
Digital CS Photography
Digital CS Photography
Videotaping Crime Scenes
Videotaping Crime Scenes
Camera Talk
Camera Talk
Camera Talk
Camera Talk
Light Talk
Light Talk
Light Talk
Light Talk
Camera Parts
Camera Parts
Protocol
Protocol
Survey The Scene
Survey The Scene
Composition
Composition
Overall Photography
Overall Photography
Medium Range Photography
Medium Range Photography
Close-up Photography
Close-up Photography
Side Lighting Photography
Side Lighting Photography
Soft Lighting & Bounce Photography
Soft Lighting & Bounce Photography
Time Exposure
Time Exposure
Painting With Light
Painting With Light
Fluorescent Photography
Fluorescent Photography
Filters in Forensic Photography
Filters in Forensic Photography
Fill Flash Photography
Fill Flash Photography
Special Techniques - Snow
Special Techniques - Snow
Fire Scenes
Fire Scenes
Specific Scene Considerations
Specific Scene Considerations
Conclusion
Conclusion

Презентация на тему: «Уроку изо по афиша цирка». Автор: LTC Mac. Файл: «Уроку изо по афиша цирка.ppt». Размер zip-архива: 3891 КБ.

Уроку изо по афиша цирка

содержание презентации «Уроку изо по афиша цирка.ppt»
СлайдТекст
1 Chapter 3

Chapter 3

Forensic Photography: An Overview to Recording the Scene

2 History

History

The camera has a long and distinguished history as a means of recording phenomena from the first use by Daguerre and Fox-Talbot, such as astronomical events (eclipses for example) and small creatures when the camera was attached to the eyepiece of microscopes (in photomicroscopy).

3 History

History

The camera also proved useful in recording crime scenes and the scenes of accidents, one of the first applications being at the scene of the Tay Rail Bridge disaster of 1879. The court, just a few days after the accident, ordered James Valentine of Dundee to record the scene using both long distance shots and close-ups of the debris. The set of accident photographs was used in the subsequent court of inquiry.

4 History

History

They show that, in the words of the Public Inquiry the bridge was badly designed, badly built and badly maintained. (Below is a picture of one of the bridge columns). The methods used in analyzing old photographs are known as forensic photography.

5 History

History

But when did actual crime scene photography begin? Mary Jane Kelly was murdered by Jack the Ripper on November 9, 1888 (5th and last victim) and photographed in her room. (newspaper photo)

6 History

History

Emma and Andrew Borden were murdered on August 4, 1892 at Fall River, Massachusetts and photographed as they were found.

7 History

History

Alphonse Bertillon started photographing crime scenes around Paris circa 1890. 19th-century revolution in forensic imaging Forensic pathologists began using pictures and words to show how various conditions appear in the cadaver, and to teach students and colleagues new methods of analysis. Line drawings, half-tone photography, and chromolithography, which could render coloration, texture, and subtle shading, became increasingly common as improvements in print technology made detailed illustrations cheaper to produce.

8 Crime Scene Photography

Crime Scene Photography

Photographs taken at a crime scene: 1. Show the layout of the crime scene 2. Show the position of collected and uncollected evidence 3. Show the point of view of victims, suspects, and witnesses 4. Show the original condition of items of evidence at the scene

8

9 Film Photography

Film Photography

Photographic film consists of a sheet of silver halide grains which “expose” when exposed to light. Film speed is a measure of the light-gathering capacity of the film. Special types of film include Polaroid film and Infrared film

9

10 Digital Photography

Digital Photography

A digital photograph is made when a light sensitive microchip captures light on each of millions of tiny picture elements, called pixels. The light is recorded on each pixel as a specific electric charge which is read by the camera as image information which is stored as a file on a memory card. The number of pixels is directly related to the resolution of the picture. Photographs with more pixels show increasingly good resolution, or more detail and sharpness in photographs. The number of pixels that a camera features is usually measured in millions of pixels, or megapixels.

10

11 Cameras

Cameras

The most commonly used camera at crime scenes is the Single Lens Reflex (SLR) camera or the Digital Single Lens Reflex (DSLR) camera. SLR and DSLR cameras allow for the use of various accessories such as lenses, flashes, and filters. SLR and DSLR cameras also allow for manual adjustment of camera settings, such as aperture and shutter speed, that affect image quality.

11

12 Lenses

Lenses

The camera lens bends light to focus an image on the film or digital microchip. The lens’s focal length, the distance between the lens and the image projected on the film or microchip, determines the area shown in the resulting photograph. Normal Lens --Focal length of 50-55mm and used for most photographs that need to be taken at a crime scene because it can show as much area as half a wall

12

13 Lenses

Lenses

Telephoto Lens -- Focal length of 100 mm or greater and used to magnify images. Wide-angle Lens --Focal length of 35 mm and used to show much more area in one photograph than a normal lens Macro Lens --Focal length of less than 50 mm and used for highly-detailed close-up photographs Multi-purpose Lens --Focal length from 28-80 mm used to take normal, wide-angle, and telephoto photographs

13

14 Aperture and Shutter Speed

Aperture and Shutter Speed

The camera aperture is a measure of the diameter of the opening of the diaphragm, which allows light to reach the film or microchip. On film or digital cameras, one adjusts the aperture by setting the f-number --The lower the f-number setting, the wider the aperture and the more light is allowed in. The shutter speed is the length of time that the film or microchip is exposed to light. The shutter speed is measured as a fraction of a second by factors of 1/2 (i.e. 1/2, 1/4, 1/8, etc).

14

15 Depth of Field

Depth of Field

The depth of field shown in a photograph is the amount of area in the foreground and background of an object in focus that is also relatively in focus. The smaller the aperture opening, the greater the depth of field will be. This means that higher f-number settings will yield higher depth of field.

15

16 DSLR Modes

DSLR Modes

The “auto mode” automatically selects an appropriate f-stop and shutter speed for conditions being photographed. The “sports mode” captures subjects in motion by using a higher (faster) shutter speed. The “night mode,” uses a lower (slower) shutter speed to gather as much light as possible to create the image. The “landscape mode” automatically selects higher f-stops to improve depth of field. The “portrait mode” selects lower f-stops to decrease the depth of field and make the subject stand out clearly against a blurred background.

16

17 Illumination

Illumination

The color temperature of a light source is “hot” if it has a bluer hue, while a “cold” light source has a red-orange hue. Light meters on film or digital cameras allow photographers to measure the amount of light in a shot. A flash unit can produce either direct reflective lighting or oblique lighting, which is achieved by positioning the flash at an angle less than 90° to the surface to show detail.

17

18 Filters

Filters

Barrier filters block one specific wavelength (color) of light from reaching the film or microchip, making areas of that color appear lighter in the photograph. Bypass filters allow only a small range of wavelengths of light to reach the film or microchip and block all others.

18

19 Tripods

Tripods

Using a tripod to take photographs eliminates the possibility of blurred photos resulting from unsteady hands. For crime scene photography, it is useful if the tripod has 1) Independently adjustable legs suitable for uneven terrain 2) A level to ensure 90? images of evidence

19

20 Crime Scene Photography Log

Crime Scene Photography Log

A log of each photograph taken at the crime scene is kept by the CS photographer. The top of the photography log form includes --case number, type of scene, date, location of scene, description of the camera and lenses being used, film type and speed (if applicable), and the photographer’s name and title For each photograph, the log records --date and time the photograph was taken, the location of the picture, the f-stop and shutter speed settings, the lighting used and the lighting angle (if applicable), and a brief description of the subject of the picture

20

21 Crime Scene Photography

Crime Scene Photography

Crime scene photographs should record the area in which the crime actually took place and all adjacent areas where important acts occurred. The most important prerequisite for photographing a crime scene is for it to be in unaltered condition. Each crime scene should be photographed as completely as possible in a logical succession. The sequence will show the overall scene first, then work down to individual pieces of evidence that jurors in the trial can easily relate back to the larger scene

21

22 Crime Scene Photography

Crime Scene Photography

Overview photographs of the entire scene and surrounding area, including points of exit and entry, are taken first. --Taken from the outside borders of the scene and from various angles --Include a “visual tag,” an object recorded in multiple overview photographs, to help visually piece the scene together Medium-range photographs show the layout of smaller significant areas of the crime scene. --Include at least one photograph of the “center” of the scene

22

23 Crime Scene Photography

Crime Scene Photography

Close-up photographs are taken last and show greater detail of individual objects or evidence. --Taken at a 90? angle to the object, with and without evidence markers and scales --For three-dimensional objects, oblique lighting may be needed to show depth details The four minimum photographs required at a crime scene are an overview photograph, a medium range photograph, a close-up photograph, and a close-up photograph with a scale.

23

24 Special Crime Scene Photography

Special Crime Scene Photography

Night photography – requires the use of external lighting or “painting with light.” Indoor photography – requires photographs of the neighborhood, points of entry and exit, and all walls, floors, and ceilings. Outdoor photography – requires location of photographs to be recorded by a Global Positioning Device or measurements from landmarks. --May include aerial photographs

24

25 Special Crime Scene Photography

Special Crime Scene Photography

Arson photography – requires photographs of the point of the fire’s origin and use of special equipment or techniques to provide maximum contrast in photographs of charred areas. May also include photographs of crowd outside scene because arsonists commonly return to scene Sexual assault photography – requires photographs of all wounds and clothing while showing discretion to the victim. Impression photography – requires oblique lighting to show details and a scale to later create a 1:1 scale photograph for comparison to footwear or tire samples.

25

26 Special Crime Scene Photography

Special Crime Scene Photography

Bloodstain photography – requires photographs of all pertinent stains and determined area of convergence or area of origin. --Bloodstains treated with luminol photographed in complete darkness Latent fingerprint photography – require photographs with a 1:1 scale using a special latent fingerprint camera or a regular camera fitted with an adapter. --Black and white film used to show greater contrast

26

27 Digital CS Photography

Digital CS Photography

Advantages of digital crime scene photography include 1. The ability to observe images immediately after taking them ensures important photographs are clear and show the best possible detail. 2. The resolution available can exceed 6 megapixels, while the maximum resolution offered by a film SLR camera is equivalent to about 5 megapixels. 3. Computer programs can stitch digital crime scene images together to create a 3-D view of the crime scene.

27

28 Digital CS Photography

Digital CS Photography

Digital images are easily manipulated using computer programs and may not show an accurate depiction of the crime scene. Digital images may lose image data or details through compression.

28

29 Digital CS Photography

Digital CS Photography

Law enforcement agencies ensure the admissibility of digital CS photographs by 1. Developing Standard Operating Procedures that must be followed 2. Saving images to writable (not rewritable) disks by lossless compression 3. Saving enhanced or altered images as separate files 4. Keeping a detailed and accurate photography log 5. Submitting testimony from the crime scene photographer as to the accuracy of the digital images

29

30 Videotaping Crime Scenes

Videotaping Crime Scenes

As with still crime scene photography, the crime scene video must include overview, medium-range, and close-up images. A narrated crime scene video combines photography and notes. --However, it is important that only one person narrates and no side conversations are captured on the video. Some video cameras can produce still photographs, but the quality is often poor. --Therefore, still photographs from a film or digital camera are still required.

30

31 Camera Talk

Camera Talk

Aperture = f-stop. It relates to the size of the opening in the lens. Moving the f-stop down one full stop doubles the amount of light let into the camera. Moving up cuts the amount of light by ?. Shutter speed refers to the time the shutter is open. A shutter speed of 1/1000 lets in less light than a shutter speed of 1/500. Film speed refers to the sensitivity of the film or the digital sensor. ISO 100 is less sensitive than ISO 400. Perspective refers to the spatial relationships in the image. Objects far away appear to be smaller and to converge along lines.

32 Camera Talk

Camera Talk

TTL refers to through the lens metering. SLR refers to single lens reflex. The preferred camera position is with your arms and elbows in as much as possible. Level tripods and the camera, and take most photos from eye level. Depth of field refers to the range of distances in which objects are in focus. An f-stop of f/22 gives greater depth of field than an f-stop of f/8.

33 Light Talk

Light Talk

Light is measure by wavelength and the unit of measurement is usually the nanometer (m x 10-10). The human eye can usually see from about 350 nanometers to about 650 nanometers, violet to red. Light for photography purposes can be manipulated by shutter speed, aperture setting, film speed, filters, exposure control, lens type, flash and extra light.

34 Light Talk

Light Talk

Side lighting can help with shadows and enhancement of detail. Time exposure allows the opportunity for more light. Fill flash and painting are adding light techniques.

35 Camera Parts

Camera Parts

Film wind lever. Shutter plane and shutter speed setting ring or device. Flash attachment or hot shoe attachment. Depth of field scale. Remember to focus, look at the f-stop and then read the f-stop on each side of the focus distance for the depth of field distance. Focusing ring. F-stop ring. Flash synch speed. View finder and TTL. ISO setting ring or menu button.

36 Protocol

Protocol

Check your equipment and make sure you have what you need. Take overall or overview, medium or mid-range, and close-up photographs. Keep a log of your photographs or images. Ensure that you have a legal right to take photographs. Do you need a search warrant or a consent to search. Maintain chain of custody of the recording medium and developed images. Does your photograph or image truly and accurately reflect what you saw with your eyes.

37 Survey The Scene

Survey The Scene

One role of the crime scene photographer is to capture as much information as possible relating to the scene. Consider the crowd and on-lookers when taking overall photos. Some agencies like to have a set of exit photos to include exterior overall photos.

38 Composition

Composition

Include references: landmarks, street signs, scales, placards. Fill the frame with the subject matter. Set the camera for the maximum depth of field for clear images. Take photos with and without placards, and with and without scales. Fill flash, if appropriate to remove shadows. Create shadows for enhancement of detail. Tell a story sequentially and thematically.

39 Overall Photography

Overall Photography

Wide angle lens with 35mm, and/or video with zoom – outdoor/indoor. Move around the points of the compass. Show overall layout of scene, and spatial relationships. May need to repeat during the investigation.

40 Medium Range Photography

Medium Range Photography

They should still show some overall reference features. They should show more detail than overall. Scales and placards might be included.

41 Close-up Photography

Close-up Photography

A tripod and remote shutter release are preferred. A 50m lens and diopters is an inexpensive method. Sequence diopters, 4 +2 +1 Focusing is crucial. Rough focus and then move the camera to the object. For cameras with adjustable lens, set the lens to the widest angle, activate the close-up icon, move the camera to the object. Always include one image with a scale for all impressions, bullet holes and bloodstains.

42 Side Lighting Photography

Side Lighting Photography

Tripod and remote flash cord are preferred. For tire track and footwear impressions take photos with the flash held at 30 – 45 degrees, and held at 12.00, 1:30. 3:00, 4:30 and 6:00 on the clock dial. Bracket photos Focus and depth of field can be crucial. Painting with flashlight can work – especially with digital.

43 Soft Lighting & Bounce Photography

Soft Lighting & Bounce Photography

May be used when other lighting methods “burn out” the image. Bounce may be from an object, ceiling, wall, and so forth. Soft lighting can be diffused lighting – through a screen or thin paper. Soft light may be with flashlight.

44 Time Exposure

Time Exposure

Most often used with Luminol, Fluorescent, and Alternate Light Sources. Tripod and remote shutter release are preferred. With Luminol, an f2.0 and 45 second exposure are standard. Bracket all time exposures.

45 Painting With Light

Painting With Light

A tripod and remote shutter release are required. Use a mid range f-stop (8 to 5.6). Set shutter speed on “B”, or use camera timer with digital and automatic cameras. Open shutter and lock, and walk to side, flashing every 15’. (May cover shutter, uncover with each flash, recover). Set flash on 40’, f/8. May use spotlight (?).

46 Fluorescent Photography

Fluorescent Photography

Usually requires tripod, remote shutter release, and barrier filter with standard 35mm camera. Orange 18 is good all around filter. A digital camera with barrier filter for real time photos. This work with Fluorescein! May require close-up techniques.

47 Filters in Forensic Photography

Filters in Forensic Photography

Alternate Light Sources and Fluorescent photos may require filters. The photo in the previous slide was taken with a #18 orange filter. A polarizing filter may be necessary to take photos through water or glass. They help reduce reflection and glare.

48 Fill Flash Photography

Fill Flash Photography

This is most often done to lighten a darkened area. It can be done in the same manner as painting with light, but with a much faster shutter speed in daylight. The photo at right is a Luminol photo, f 2.0, two minute exposure, then bounce flash from the ceiling of the shower to fill in the shower area after the two minute exposure.

49 Special Techniques - Snow

Special Techniques - Snow

Photographing at night, in snow, can present special problems. Soft light suing MagLites is a possibility. Lightly dusting the impression with a “dry” fingerprint brush is an alternative. Follow local policy on dusting impressions – photo first without dust. Painting with light is another technique – especially with digital.

50 Fire Scenes

Fire Scenes

Fires may leave numerous obvious and subtle patterns. Fire damage may leave a very dark scene overall, with bright spots. It is very important to bracket photos at fire scenes. Consider enhancing flash settings by one stop or more. Fire scenes usually require more light than other scenes due to the absorption of light by the dark surfaces.

51 Specific Scene Considerations

Specific Scene Considerations

Photograph a persons face and the injuries in domestic violence, assault and other crimes of violence. Fill flash in damaged shaded areas in vehicle accidents, and objects of interest in shaded areas in other scenes. Photo entry and exit in scenes. Increase the light at fire scenes. Include at least one photo or image with a scale for all impressions, bullet holes, and bloodstains and trace evidence.

52 Conclusion

Conclusion

Take exit photos. Inventory your equipment. Secure your recording medium and mark for chain of custody. Enhance images from copies. Record enhancement techniques step-by step. Establish throughout the photography process where you were at and where it was at – this usually requires noting times and dates. Prepare appropriate photography narrative reports.

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