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Related to latent image: See also body image. The undeveloped image on an exposed x-ray film; it becomes visible after chemical processing. It is the deposition of reduced silver atoms in particles or zones that causes the black zones or foci on the film.
The amount of silver deposited depends on the intensity of the initial radiation x-ray exposure. Used particularly in fluoroscopy and viewing directly or indirectly through a television camera and monitor, cineradiography, videotape or split-film device. It requires exposure to a developer and fixer before the image is visible and permanent. References in periodicals archive? Since then, understanding of the mechanism of sensitivity and latent image formation has been greatly improved.
One very important way to increase photographic sensitivity is to manipulate the electron traps in each crystal. A pure, defect-free crystal exhibits poor photographic sensitivity, since it lacks a shallow electron trap that facilitates the formation of a latent image.
In such a case, many of the photoelectrons will recombine with the silver halide crystal and be wasted. Shallow electron traps are created by sulfur sensitization, introduction of a crystalline defect edge dislocation , and incorporating a trace amount of non-silver salt as a dopant. The location, kind and number of shallow traps have a huge influence on the efficiency by which the photoelectrons create latent image centers, and consequently, on photographic sensitivity.
Another important way to increase photographic sensitivity is to reduce the threshold size of developable latent images.
Gold sensitization of Koslowski creates metallic gold specks on the crystal surface, which by itself does not render the crystal developable. When a latent image is formed around the gold speck, the presence of gold is known to reduce the number of metallic silver atoms necessary to render the crystal developable. Another important concept in increasing photographic sensitivity is to separate photoholes away from photoelectrons and sensitivity sites. This should reduce the probability of recombination. Reduction sensitization is one possible implementation of this concept. The recent 2-electron sensitization technique is built on this concept.
However, the scientific understanding of the behavior of photoholes is more limited than that of photoelectrons. On the other hand, a deep electron trap or a site that facilitates recombination will compete for photoelectrons and therefore reduces the sensitivity. However, these manipulations are used, for example, to enhance contrast of the emulsion. Reciprocity law failure is a phenomenon where the same amount of exposure irradiance multiplied by duration of exposure produces different image density when the irradiance and thus duration is varied.
There are two kinds of reciprocity failure.
They are both related to poor efficiency of utilizing photoelectrons to create latent image centers. High intensity reciprocity failure HIRF is common when the crystal is exposed by intense but brief light, such as flash tube.
This reduces photographic speed and contrast. This is common with emulsions optimized for highest sensitivity with long exposure using old emulsion technology. HIRF is due to creation of many latent subimages that are not developable due to small size. Because of brief and intense exposure, many photoelectrons are created simultaneously.
They make many latent subimages that cannot render the crystal developable , rather than one or a few latent images that can. HIRF can be improved by incorporating dopants that create temporary deep electron traps, optimizing the degree of sulfur sensitization, introducing crystalline defects edge dislocation. In recent years, many photographic prints are made by scanning laser exposure. Each location on a photographic paper is exposed by a very brief but intense laser.
Problems due to HIRF were the major technical challenge in development of such products. Paper manufacturers use dopants and precise control of the dislocation sites to improve to virtually eliminate HIRF for this new application. Low intensity reciprocity failure LIRF occurs when the crystal is exposed with weak light of long duration, such as in astronomical photography.
A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film. When photographic film is. Latent image, in photography, the invisible configuration of silver halide crystals on a piece of film after exposure to image-bearing focussed light; it is.
LIRF is due to inefficiency of forming a latent image, and this reduces photographic speed but increases contrast. Due to low level of exposure irradiance intensity , a single crystal may have to wait for a significant amount of time between absorbing sufficient number of photons. Contact our editors with your feedback. You may find it helpful to search within the site to see how similar or related subjects are covered. Any text you add should be original, not copied from other sources.
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