Contents:
Photographers must understand principles of photography first. When the photographers take the photographs itself, they must consider three components. The three components are ISO, Shutter speed and aperture. The International Organization for Standardization ISO is an international standard-setting body composed of representatives from various national standards organizations. By adjusting ISO, the photographs can be shown differently in same environment. In dark environment, ISO makes light sensor of camera more sensitive. It helps photographers to meet proper light in dark or harsh condition.
Among above two photographs, the photograph 2 is a proper representation because it shows clear objects with proper brightness. However, ISO has high possibility to make camera noise which is visual distortion. Too much dependence on ISO can distort the image. For that reason, the photographers must understand ISO before using it. Shutter speed is the length of time when the film or digital sensor inside the camera is exposed to light.
Object and image can be shown differently by shutter speed. Below are the examples. These two photographs are taken under same situation except for camera shutter speed. In above situation, slow shutter speed makes image more clear and bright because the low shutter speed takes more light than high shutter speed.
However, the high shutter speed often is necessary for moving object.
Above two photographs are taken under same situation except for camera shutter speed. In case of moving object, the low shutter speed is not proper to capture the object. It needs faster shutter speed to capture it. Shutter speed has pros and cons. For capturing a moving object, photographers must use a high shutter speed.
However, the image can be very dark. Low shutter speed must be used when capturing a clear image or object under the harsh condition, but it is hard to capture the moving objects.
Forensic Uses of Digital Imaging, Second Edition distills his classroom and workshop material to present the information most relevant to forensic science. Forensic Uses of Digital Imaging [John C. Russ] on giuliettasprint.konfer.eu *FREE* shipping on qualifying offers. The ability to work with, and retrieve images, is vital to.
Aperture means that the extent of a sharpness of an image that is shown through the lens. So, it is one of really important things to photographers. High aperture High focus means hard sharpness like photograph1. Every Low aperture low focus means soft sharpness. The photograph 1 shows all objects very clearly because of the high aperture.
The photograph 2 image shows an object with right focus but rest of the objects are all blurred because of low aperture.
All Languages. Road traffic incident RTI photographs show the overall layout at the scene taken from many different angles, with close-ups of significant damage, or trace evidence such as tire marks at a traffic collision. Figure 7 Fingerprint image. He has also received the Ernst Abbe Memorial Award from the New York Microscopical Society for his contributions to the field of microscopy as a developer of computer-assisted microscopy and image analysis. Variations can be made either throughout the picture or in specific parts. Histogram operations include histogram stretch.
External flash units are helpful tools when responding to a crime scene and for the proper documentation of evidence. The white balance of a photo flash unit is set to mimic daylight to ensure the proper color balance of the subject matter. The photographer must be mindful of the reflections that can occur due to the directionality of the flash and the position of the subject matter.
To avoid flash reflections, as demonstrated below examples, the flash must either be removed from the camera body, creating an angle, or bounced off of the ceiling. The tools required to properly document the crime scene include: [9]. The images must be clear and usually have scales. They serve to not only remind investigators of the scene, but also to provide a tangible image for the court to better enable them to understand what happened.
The use of several views taken from different angles helps to minimise the problem of parallax. Overall images do not have scales and serve to show the general layout, such as the house where the murder is thought to have occurred. Context images show evidence in context, like how the knife was next to the sofa.
Close up images show fine detail of an artifact, such as a bloody fingerprint on the knife. Road traffic incident RTI photographs show the overall layout at the scene taken from many different angles, with close-ups of significant damage, or trace evidence such as tire marks at a traffic collision.
As with crime scene photography, it is essential that the site is pristine and untouched as far as is possible. Some essential intervention, such as rescuing a trapped victim, must be recorded in the notes made at the time by the photographer, so that the authenticity of the photographs can be verified.
As with all evidence a chain of custody must be maintained for crime scene photographs. Regardless of how it is done any person who handles the evidence must be recorded. Secure Digital Forensic Imaging methods may be applied to help ensure against tampering and improper disclosure.
However John cautions that it is not about the equipment:. It's not what [equipment] you have, but the way you use it. Forensic teams work to UK Home Office's Digital Imaging Procedures for the collection of evidence in order to ensure that it is procured consistently and to a minimum standard. The requirement is for a genuine "original" to be stored: during the infancy of digital imaging, this would have been on write-once optical discs, but now the use of secure access file servers is standard practice.
The size of the job is directly related to the amount of evidence that requires recording. For scene of crime documentary evidence this could be as few as four or eight photos shot from the four corners and four walls , ranging to many hundreds depending on the complexity and number of marks and size of the scene which would cover the evidence at a range of scales in increasing detail.
In the example below, the complexity of the scene was increased due to the presence of blood spatter marks. A small company of around 50 staff, it quickly grew and was acquired by LGC Forensics with a roll of over people and is now Eurofins!
So what was it that he found interesting about the job? More generally, John says it's the "variability of the job. I followed up by asking John what the strangest or most interesting job was. Given the wide range of experience he has had, it was never going to be one! In terms of the strangest, he was called to a private job at a flat in West London but was not told who the client was or why the evidence was required.
On arrival they found a whole series of marks left in excrement smeared across the floor. When they had finished, one of the occupants of a neighboring flat asked who they were and why they were there.
Apparently an inexplicable job that no one seemed to be able to make sense of! In Marion Ross was murdered in Kilmarnock, Scotland.
Subsequently, finger marks of Shirley McKie, a serving police constable, were identified at the crime scene. She testified that she had never been at the scene which subsequently called in to question the ability of the fingermark specialists to correctly identify evidence. David Asbury was convicted of Ross' murder, but subsequently released from a life sentence on the basis of this mistake. The marks remain unidentified.
The case was reopened in and John worked on the original photographs of the finger marks, but not the finger marks themselves. Finger mark expert witnesses used this evidence and it has perhaps become the single most studied finger mark image ever. What is startling about this inquiry and the interpretation of the image is that the inquiry never looked at the original evidence, only the images. This highlights a more general word of caution from John.