202

also known as the H and D curve, is a representation of the response of a screen film radiograph to light; is the graph shows the relationship between log of exposure and the density produced in the film.

H and D means

measure’s film’s response to exposure and processing; the study of the response of an IR to x-rays; scientific study of light-sensitive materials.

a device for measuring the sensitivity of photographic equipment to light.

an instrument for measuring the photographic density of an image on a film or photographic print.region represents higher exposures and is relatively flat.

refers to the portion between points 1 and 2 in the diagram; the region of the curve indicates very low exposures

refers to the section of the curve between 2 and 3 on the diagram; the region is the approximate linear response range, where OD is proportional to the log of the exposure.

this refers to the portion between 3 and 4 on the diagram; region represents higher exposures and is relatively flat.

what are the three regions distinct in the characteristic curve?

the amount of exposure increase needed to produce a change in optical density

refers to a maximum density; maximum point dose to an organ or tumor target in radiotherapy cancer treatment.

(Minimum density) is the corresponding expression of the lowest achievable density.

it is the slope of the tangent at any point on the characteristic curve.

is the slope of a line connecting a point on the characteristic curve 0.25 above base + fog and a point 2.0 above base + fog.

is defined as the slope of the characteristic curve between net optical densities 0.25 and 2.

density means the optical density of a film due to its base density plus any action of the developer on the unexposed silver halide crystals; also called BASIC FOG which is usually up to 0.2.