Photograph alteration detection
Photograph alteration detection refers to the techniques used to determine if photographs have been modified in any way, impacting their representation of subjects. This practice has gained significance with the rise of digital photography, as the tools available for altering images have become more sophisticated and accessible. Traditional film photographs, when altered, often leave noticeable chemical marks or brushstrokes, making detection relatively straightforward. In contrast, digital images can be edited seamlessly, allowing for more subtle alterations that can be difficult to identify.
As courts increasingly rely on photographic evidence, they require thorough testing to confirm the integrity of images before they can be admitted as evidence. Law enforcement agencies often employ specialized technology, such as software that examines digital watermarks, to verify whether an image has been altered. There are ongoing debates regarding the reliability of photographic evidence, especially given the potential for new alteration techniques to outpace detection methods. Some experts even question the admissibility of digital images in court, highlighting concerns about the implications of intentional alterations by forensic scientists. This evolving landscape underscores the necessity for robust methodologies in detecting photograph alterations to maintain the integrity of visual evidence.
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Subject Terms
Photograph alteration detection
DEFINITION: Techniques used to determine whether photographs have been altered in any way to change the nature of the portrayal of their subjects.
SIGNIFICANCE: People have altered photographs for many reasons since the invention of film photography, and forensic scientists have long been called upon to examine photographs for evidence of alteration. With the advent of digital photography, the ready availability of sophisticated tools and techniques for altering images has posed an increasingly difficult problem for investigators who must rely on photographs as evidence in criminal and other legal cases.
The alteration of a photograph taken with a film camera requires the use of brushing techniques that cover or chemically remove parts of the image. All basic methods of film photo alteration leave very obvious traces of the alteration process in the form of chemical marks and brushstrokes. Even skillful alteration of film photographic prints can generally be detected easily through the use of computer software that registers changes in lighting, positioning, or displacement of the subjects in the prints with respect to horizontal and vertical planes of reference. The alteration of digital images is usually more subtle. Digital images can be copied, edited, and shared without loss of image quality. Software programs that allow users to alter digital images, such as Adobe Photoshop, are readily available and widely used. Artificial intelligence (AI) can also be used to alter digital images.
In the past, criminal and civil courts were willing to admit video recordings and photographs as reliable evidence without much question. Given the ease with which digital images can be altered, however, courts now require that photographs and digital video images undergo tests to determine if they have been altered before they can be admitted as evidence. Virtually all law-enforcement agencies in the United States routinely use specialized technology to determine the integrity of digital images.
Many images produced by digital cameras contain within them a kind of coding known as watermarking; this coding preserves records of the original images. Digital watermarks are not visible to the eye, but they can be detected through the use of certain software. Such software can tell users whether primary digital images have been altered by comparing the images with the information stored in their watermarks. Some law-enforcement agencies make use of sophisticated image-processing software to restore altered digital images to their original forms.
Because of the increasing ease of altering digital images and the possibility that forensic scientists’ capability of detecting such alterations may be surpassed by new techniques of alteration, some observers have urged caution in the use of photographic evidence, and others have gone so far as to suggest that courts should not admit digital images as evidence. The use of intentional alteration of images by forensic scientists, as in the digitizing of surveillance tapes to sharpen their images, has also come into question. For example, a dark spot on an image may sharpen under one resolution to reveal an object resembling a gun, whereas under another resolution, the object may appear to be a knife, or it may be revealed to be simply a spot or blotch on the original image. Many have argued that evidence produced using such an unreliable technique should not be admitted in court.
Bibliography
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