1.1 本试验方法包括按照规则透射率测量塑料薄膜的透明度( T r )。尽管通常适用于任何半透明或透明材料，但它主要用于名义上透明无色的薄板。 1.2 以国际单位制表示的数值应视为标准。括号中给出的值仅供参考。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 注1: 目前还没有与该标准等效的ISO。 注2: 有关其他信息，请参见术语 E284年 和实践 E1164美元 。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 4.1 纸张清晰度的属性，通过其传输图像的能力来衡量- 形成光的折射率与其规则的透射率相关。对差异的敏感性随着入射光束和接收器角度的减小而提高。如果入射光束和接收器孔径的角宽度（从样品位置看）为0.1°或更小，则具有商业价值的片材的透明度范围约为10至90 % 如通过该测试测量的。使用这种测试方法获得的结果在很大程度上受到仪器设计参数的影响；例如，分辨率在很大程度上由接收器孔径的角度宽度决定。 因此，在比较不同仪器获得的结果时应格外小心，尤其是对于规则透射率较低的样品。 4.2 根据该测试方法的规则透射率数据与通常称为“透视”的特性相关，该特性是通过手持样本对观察者清晰区分相对较远目标的能力的影响主观评定的。由于视觉测试中散射光的干扰，这种相关性对于高散射材料来说很差。

1.1 This test method covers the measurement of the transparency of plastic sheeting in terms of regular transmittance ( T r ). Although generally applicable to any translucent or transparent material, it is principally intended for use with nominally clear and colorless thin sheeting. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 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. Note 1: There is no known ISO equivalent to this standard. Note 2: For additional information, see Terminology E284 and Practice E1164 . 1.4 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. ====== Significance And Use ====== 4.1 The attribute of clarity of a sheet, measured by its ability to transmit image-forming light, correlates with its regular transmittance. Sensitivity to differences improves with decreasing incident beam- and receptor-angle. If the angular width of the incident beam and of the receptor aperture (as seen from the specimen position) are of the order of 0.1° or less, sheeting of commercial interest have a range of transparency of about 10 to 90 % as measured by this test. Results obtained by the use of this test method are greatly influenced by the design parameters of the instruments; for example, the resolution is largely determined by the angular width of the receptor aperture. Caution should therefore be exercised in comparing results obtained from different instruments, especially for samples with low regular transmittance. 4.2 Regular transmittance data in accordance with this test method correlate with the property commonly known as “see-through,” which is rated subjectively by the effect of a hand-held specimen on an observer's ability to distinguish clearly a relatively distant target. This correlation is poor for highly diffusing materials because of interference of scattered light in the visual test.