Designation: E808 − 01 (Reapproved 2016)Standard Practice forDescribing Retroref l ection 1This standard is issued under the f i xed designation E808; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides terminology, alternative geo-metrical coordinate systems, and procedures for designatingangles in descriptions of retroref l ectors, specif i cations forretroref l ector performance, and measurements of retroref l ec-tion.1.2 Terminology def i ned herein includes terms germane toother ASTM documents on retroref l ection.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards: 2E284 Terminology of Appearance2.2 Federal Standard:Fed. Std. No. 370 Instrumental Photometric Measurementsof Retroref l ecting Materials and Retroref l ecting Devices 32.3 CIE Document:CIE Publication No. 54 Retroref l ection-Def i nition and Mea-surement 43. Terminology3.1 Terms and def i nitions in Terminology E284 are appli-cable to this standard.3.1.1 In accordance with the convention appearing in theSignif i cance and Use section of Terminology E284, the super-script B appearing after [CIE] at the end of a def i nitionindicates that the given def i nition is a modif i cation of that citedwith little difference in essential meaning.N OTE 1—The terminology given here describes visual observation ofluminance as def i ned by the CIE V (λ) spectral weighting function for thephotopic observer. Analogous terms for other purposes can be def i ned byusing appropriate spectral weighting.3.2 Def i nitions:3.2.1 The delimiting phrase “in retroref l ection” applies toeach of the following def i nitions when used outside the contextof this or other retroref l ection standards.3.2.2 coeff?cient of line retroref l ection, R M , n—of a retrore-f l ecting stripe, the ratio of the coefficient of luminous intensity(R I ) to the length (l), expressed in candelas per lux per metre(cd·lx –1 ·m –1 ). R M = R I /l.3.2.2.1 Discussion—R M depends on the spectral composi-tion of the illumination which is usually CIE illuminant A.3.2.3 coeff?cient of luminous intensity, R I , n—of aretroref l ector, ratio of the luminous intensity (I) of the retrore-f l ector in the direction of observation to the illuminance (E ' )at the retroref l ector on a plane perpendicular to the direction ofthe incident light, expressed in candelas per lux (cd·lx –1 ). R I =(I/E ' ).3.2.3.1 Discussion—In a given measurement one obtains theaverage R I over the solid angles of incidence and viewingsubtended by the source and receiver apertures, respectively. Inpractice, I is often determined as the product of the illuminanceat the observer and the distance squared (I = E r d 2 ). R I dependson the spectral composition of the illumination which is usuallyCIE illuminant A.3.2.3.2 Discussion—Also called coeff?cient of (retrore-f l ected) luminous intensity. Equivalent commonly used termsare CIL and SI (specif i c intensity). CIE Publication 54 uses thesymbol R for R I . The ASTM recommendation is to use thesymbol R I .3.2.4 coeff?cient of retroref l ected luminance, R L , n—the ratioof the luminance, L, in the direction of observation to thenormal illuminance, E ' , at the surface on a plane normal to theincident light, expressed in candelas per square metre per lux[(cd·m –2 )·lx –1 ].R L 5 ~ L/E ' ! 5 ~ R I /Acosν ! 5 ~ I/EAcosν ! 5 ~ R A /cosν ! (1)1 This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.10 on Retrore-f l ection.Current edition approved Jan. 1, 2016. Published January 2016. Originallyapproved in 1981. Last previous edition approved in 2009 as E808 – 01 (2009).DOI: 10.1520/E0808-01R16.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.3 Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098, http://www.dodssp.daps.mil.4 Available from U.S. National Committee of the CIE (International Commissionon Illumination), C/o Thomas M. Lemons, TLA-Lighting Consultants, Inc., 7 PondSt., Salem, MA 01970, http://www.cie-usnc.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1 Copyright by ASTM Int'l (all rights reserved); Thu Aug 3 12:38:02 EDT 2017Downloaded/printed byUniversity of Edinburgh (University of Edinburgh) pursuant to License Agreement. No further reproductions authorized.
