【国外标准】 Standard Reference Radiographs for Appearances of Radiographic Images as Certain Parameters are Changed

4.1 A key consideration with any radiographic system is its contrast resolution and spatial resolution capability (that is, sensitivity). The degree of obtainable sensitivity with a given system is dependent upon several radiographic parameters such as source energy level, film system class, type and thickness of intensifying screens, and material thickness radiographed. These reference radiographs permit the user to estimate the degree of sensitivity change that may be obtained when these parameters are varied from a specific technique. This standard may also be used in conjunction with Test Method E1815 or with Practice E746 or Test Method E1735 to provide a basis for developing data for evaluation of a user's specific system. This data may assist a user in determining appropriate parameters for obtaining desired degrees of radiographic system sensitivity.1.1 This document describes the appearance of a radiographic image where fundamental components of image quality are changed, that is, variables such as whether an X-ray or gamma ray source was used, the characteristics of the radiographic film (gradient, granularity, and developing conditions) and intensifying screens, and specimen thickness (the geometrical configuration of the radiographic set-up and focal spot size both affect image quality but are not considered in the reference radiographs).1.2 The X-ray film systems used in obtaining the illustrative data were as follows: Very Fine Grain (comparable to class I of Test Method E1815) and Fine Grain (comparable to class II of Test Method E1815).1.3 These reference radiographs2 consist of four composite illustrations3 and show how such factors as radiation energy, specimen thickness, and film properties affect the radiographic image. The reference radiograph films are an adjunct to this document and must be purchased separately from ASTM if needed.1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.