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a branch of photographic sensitometry devoted to measurements of the absorption and scattering of light by developed photographic layers.

The methods of densitometry make possible the quantitative evaluation of the final photographic effect based on the optical density of blackening in the photosensitive layer. There is a nearly linear relationship between the surface concentration of silver in the blackened area and the optical density; their ratio is called the photometric equivalent of blackening. The optical density increases with the degree of dispersion of the silver in the blackened area. Correspondingly, the extent of the optical usefulness of the silver in the blackened area increases with the disperseness of the silver halide in the original light-sensitive layer and with the relative magnitude of the exposure of this layer to light. Because of the nonhomogeneous nature of the blackened areas, the light absorption in these areas is accompanied by strong diffusion. Therefore, the magnitude of optical density depends on the geometric structure (aperture) of the light beams that are incident on the blackened area and are directed to a receiver after passing through the blackened area.

A distinction is made between regular density (D ║) and integral density (DE), which are measured upon illumination of the blackened area by a beam of parallel light rays and upon reception, in the first case, of only that part of the light beam that has not changed direction during passage through the blackened area and, in the second case, of the entire light beam. In addition, diffuse density (D#), which is measured using an ideally diffuse beam of light to illuminate the blackened area, and effective density (D ψ), which is measured under intermediate conditions encountered in practice, are also distinguished. The difference D ║ -DE is a measure of the light diffusion in blackened areas. The diffuse density is commonly used in sensitometry.

The optical density of blackening is measured using densitometers and microphotometers.

The measurement of color fields in developed materials for color photography constitutes a special branch of densitometry.

References in periodicals archive ?
At this point, it is physicians' concern for patients, not the payment, that motivates them to continue to offer bone densitometry services, said Dr.
Thus, the purpose of the present study was to establish a bilateral comparative analysis of the mandibular angle bone density, considering the morphological characteristics, from young patients of both genders, in a highly mixed population such as the Brazilian population, through computerized bone densitometry, being useful as a complementary exam for future treatments that involve bone structures that consists the stomatognathic system.
The current guidelines suggest that clinicians should take into account a number of risk factors before ordering bone densitometry for them.
Sins and her associates said, noting that all three peripheral bone densitometry sites tested in the NORA study were equally effective for predicting fracture risk.
The eligibility requirements for the bone densitometry examination follow the same model established for other ARRT postprimary certification programs; that is, registration in a supporting category and documentation of clinical experience specific to the discipline.
Koshy said, suggest that "focused use of bone densitometry in women younger than 50 with any of these risk factors can help to identify patients with future fracture risk who may merit osteoporosis prevention.
CHICAGO -- Bone densitometry readings at the heel, forearm, and finger are all about equal in their ability to help physicians identify white women at risk of fracturing any of their hones within the next year, Kenneth G.
While bone densitometry measurements taken at central sites such as the hip or spine remain the best modality for diagnosing osteoporosis and its severity the study results suggest that densitometry measurements taken at peripheral sites are acceptable for screening and identifying women who require further bone evaluation and possibly treatment, Dr.