ASTM E808-01

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E 808 – 01
Standard Practice for
1
Describing Retroreflection
This standard is issued under the fixed designation E 808; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
luminance as defined by the CIE V (l) spectral weighting function for the
1. Scope
photopic observer. Analogous terms for other purposes can be defined by
1.1 This practice provides terminology, alternative geo-
using appropriate spectral weighting.
metrical coordinate systems, and procedures for designating
3.2 Definitions: The delimiting phrase “in retroreflection”
angles in descriptions of retroreflectors, specifications for
applies to each of the following definitions when used outside
retroreflector performance, and measurements of retroreflec-
the context of this or other retroreflection standards.
tion.
3.2.1 coeffıcient of line retroreflection, R , n—of a retrore-
M
1.2 Terminology defined herein includes terms germane to
flecting stripe, the ratio of the coefficient of luminous intensity
other ASTM documents on retroreflection.
(R ) to the length (l), expressed in candelas per lux per metre
I
1.3 This standard does not purport to address all of the
–1 –1
(cd·lx ·m ). R = R /l.
M I
safety concerns, if any, associated with its use. It is the
3.2.1.1 Discussion—R depends on the spectral composi-
M
responsibility of the user of this standard to establish appro-
tion of the illumination which is usually CIE illuminant A.
priate safety and health practices and determine the applica-
3.2.2 coeffıcient of luminous intensity, R , n—of a retrore-
I
bility of regulatory limitations prior to use.
flector,ratiooftheluminousintensity(I)oftheretroreflectorin
2. Referenced Documents the direction of observation to the illuminance (E )atthe
'
retroreflector on a plane perpendicular to the direction of the
2.1 ASTM Standards:
–1
2
incident light, expressed in candelas per lux (cd·lx ). R =
I
E 284 Terminology of Appearance
(I/E ).
'
2.2 Federal Standard:
3.2.2.1 Discussion—In a given measurement one obtains
Fed. Std. No. 370 Instrumental Photometric Measurements
3
the average R over the solid angles of incidence and viewing
I
of Retroreflecting Materials and Retroreflecting Devices
subtended by the source and receiver apertures, respectively. In
2.3 CIE Document:
practice, Iisoftendeterminedastheproductoftheilluminance
CIE Publication No. 54, Retroreflection-Definition and
2
4
at the observer and the distance squared (I=E d ). R depends
r I
Measurement
onthespectralcompositionoftheilluminationwhichisusually
3. Terminology
CIE illuminant A.
3.2.2.2 Discussion—Also called coeffıcient of (retrore-
3.1 Terms and definitions in Terminology E 284 are appli-
flected) luminous intensity. Equivalent commonly used terms
cable to this standard.
are CIL and SI (specific intensity). CIE Publication 54 uses the
3.1.1 In accordance with the convention appearing in the
symbol R for R . The ASTM recommendation is to use the
Significance and Use section of Terminology E 284, the I
symbol R .
superscript B appearing after [CIE] at the end of a definition I
3.2.3 coeffıcient of retroreflected luminance, R , n—the
indicates that the given definition is a modification of that cited L
ratio of the luminance, L, in the direction of observation to the
with little difference in essential meaning.
normal illuminance, E , at the surface on a plane normal to the
'
NOTE 1—The terminology given here describes visual observation of
incident light, expressed in candelas per square metre per lux
–2 –1
[(cd·m )·lx ].
1
This practice is under the jurisdiction of ASTM Committee E12 on Color and
R 5 L/E ! 5 R /A cos n! 5 I/EA cos n! 5 R / cos n! (1)
~ ~ ~ ~
L ' I A
Appearance and is the direct responsibility of Subcommittee E12.10 on Retrore-
flection.
where:
Current edition approved Dec. 10, 2001. Published February 2002. Originally
A = surface area of the sample, and
published as E 808 – 81. Last previous edition E 808 - 99a.
2
n = viewing angle.
Annual Book of ASTM Standards, Vol 06.01.
3
Available from Standardization Documents Order Desk, Bldg. 4 Ave., Phila-
3.2.3.1 Discussion—The units millicandela per square me-
delphia, PA 19111-5094, Attn: NPODS. –2 –1
tre per lux [(mcd·m )·lx ] are usually used to express the R
4 L
Available from USNC/CIE Publications Office, TLA Lighting Consultants,
values of road marking surfaces. This quantity is also referred
Inc., 7 Pond St., Salem, MA 01970.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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E808–01
to as specific luminanc
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