Sharpness And Resolution

Sharpness And Resolution

Write a short note on sharpness and resolution.
Answer.

Sharpness or detail

Sharpness refers to the capability of X-rays to reproduce distinct outlines of an object or to reproduce the small details of an object on a dental radiograph.

Radiographic sharpness

Resolution or Definition

Resolution, or resolving power of the film, is a measure of the film’s ability to differentiate between different structures and record separate images of small objects placed very close together, and is measured in line pairs per mm.

“Common challenges in explaining sharpness and resolution effectively: FAQs provided”

A certain degree of unsharpness is present in all dental radiographs.

The fuzzy, unclear area that surrounds a radiographic image is termed ‘penumbra’.

“Understanding the role of sharpness and resolution in photography: Q&A explained”

Various Factors that control the sharpness of an image on the X-ray Film are

• Geometric unsharpness: This type of unsharpness is due to the criss-crossing of rays at the edges of the object, resulting in a fuzzy image border. Size of the focal spot and target object distance affect geometric unsharpness.
• Size of the focal spot: Smaller the focal spot, sharper is the image produced. When a “point source” is used, (the normal focal spot size is 0.6 mm2 to 1 mm2) and non – sharpness is produced.
• Object-film distance: This should be as small as possible to obtain a sharper image.
• Target-object distance: Should be as large as possible for obtaining a sharp image.
• Motion unsharpness: It is caused by any movement of either the patient, tube, or film during the exposure.

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Radiographic image quality

• Absorption unsharpness: It is caused due to variation in object shape, e.g. cervical burn—out at the neck of a tooth.
• Intensifying screen unsharpness: It is caused by the diffusion as well as spread of the light emitted from intensifying screens. Intensifying screen reduces the exposure time so there are less chances of movement of patient, tube or film so motion unsharpness is reduced.
• Fog unsharpness: Scattered, stray, leakage or any other radiation not belonging to primary beam is undesirable as it produces film fog. For intra-oral films, filtration, collimation and film packets with lead back sheets should be used to reduce the secondary radiation. For extra-oral films grids are used to reduce secondary radiation. Use of unsafe light produces fog in darkroom.
• Poor resolution: Resolution is determined mainly by characteristics of the film including: type, direct or indirect action, speed, and silver halide emulsion crystal size.