1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 22891:2013Paper Determination oftransmittance by diffusereflectance measurementBS ISO 22891:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implement
2、ation of ISO 22891:2013. Itsupersedes BS ISO 22891:2007 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PAI/11, Methods of test for paper, board and pulps.A list of organizations represented on this committee can beobtained on request to its secretary.T
3、his publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 77261 0ICS 85.060Compliance with a British Standard cannot confer immu
4、nity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 March 2013.Amendments issued since publicationDate Text affectedBS ISO 22891:2013 ISO 2013Paper Determination of transmittance by diffuse reflectance measurementPapi
5、er Dtermination de la transmittance par le mesurage de la rflectance diffuseINTERNATIONAL STANDARDISO22891Second edition2013-03-01Reference numberISO 22891:2013(E)BS ISO 22891:2013ISO 22891:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwi
6、se specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address bel
7、ow or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 22891:2013ISO 22891:2013(E) ISO 2013 All rights reserved iiiContents PageForewor
8、d ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 35 Apparatus . 36 Sampling 47 Preparation of test pieces . 48 Procedure. 49 Calculation 410 Test report . 5Annex A (normative) Spectral characteristics of reflectometers for measuring luminous reflectance fac
9、tors 6Annex B (informative) Relationship between transmittance and opacity 8Annex C (informative) Precision . 9Bibliography .11BS ISO 22891:2013ISO 22891:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies)
10、. The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non
11、-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part
12、2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a
13、vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 22891 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.This second editio
14、n cancels and replaces the first edition (ISO 22891:2007), of which it constitutes a minor revision.iv ISO 2013 All rights reservedBS ISO 22891:2013ISO 22891:2013(E)IntroductionThis International Standard presents a method of determining the transmittance indirectly from reflectance factor data obta
15、ined by measurement under specified conditions. The equation used to calculate the transmittance is based on the Kubelka-Munk theory of light scattering and light absorption, and the equation can therefore only be strictly applied if measurements are made on materials which scatter light sufficientl
16、y to justify the application of this theory.The reflectance factor depends on the conditions of measurement, and particularly on the spectral and geometric characteristics of the instrument used for its determination. This International Standard should therefore be read in conjunction with ISO 2469
17、and ISO 2471.The transmittance value obtained by this method is a single value compatible with the opacity value determined according to ISO 2471, since all measurements are related to the luminance factor calculated with respect to the CIE illuminant C.The method described in this International Sta
18、ndard gives only the total transmittance and does not distinguish between regular transmittance and diffuse transmittance. It does not provide a direct measure of the ability to distinguish, for example, written text through a transparent medium. This can be assessed only if the ratio of the regular
19、 to the diffuse transmittance is known.It is emphasized that this method is for the determination not of the transmittance by direct measurement but of the transmittance obtained indirectly from reflectance factor measurements. Under ideal conditions, they are the same, but in practice, it can be ne
20、cessary to emphasize the difference. ISO 2013 All rights reserved vBS ISO 22891:2013BS ISO 22891:2013Paper Determination of transmittance by diffuse reflectance measurement1 ScopeThis International Standard specifies a method for the calculation of transmittance based upon diffuse reflectance measur
21、ements.The use of the method is restricted to white and near-white translucent papers (see 3.9). If it is necessary to determine the transmittance of papers which contain fluorescent whitening agents, the fluorescence emission is eliminated using the prescribed UV cut-off filter.NOTE This means that
22、, although this International Standard refers to ISO 2469, which permits the use of both filter colourimeters and abridged spectrophotometers, a filter colourimeter with no means of eliminating the emission of fluorescence is not suitable for this type of measurement if fluorescent whitening agents
23、are present.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 186, Paper a
24、nd board Sampling to determine average qualityISO 2469, Paper, board and pulps Measurement of diffuse radiance factor (diffuse reflectance factor)ASTM E308-06, Standard Practice for Computing the Colors of Objects by Using the CIE System3 Terms and definitionsFor the purposes of this document, the f
25、ollowing terms and definitions apply.3.1reflectance factorRratio of the radiation reflected by a body to that reflected by the perfect reflecting diffuser under the same conditions of illumination and detectionNote 1 to entry: This ratio is often expressed as a percentage.3.2luminance factor (C)Ryre
26、flectance factor weighted with reference to the colour matching function y () of the CIE 1931(2) Standard Observer and the CIE illuminant CNote 1 to entry: This property corresponds to the attribute of visual perception of the luminance of the reflecting surface. The strict definition refers to the
27、luminous efficiency function (for photopic vision) V(). Since this function is identical with the y () function, the latter is preferred here, since it is more familiar in a paper technology context and it is this function which is indicated in connection with the ASTM E308 tables necessary for the
28、computations.Note 2 to entry: Since the concept of “luminance” in this International Standard is strictly for small fields of view, it only embodies the y () function of the CIE 1931(2) Standard Observer. Thus, it is sufficient to only add the qualification (C) to indicate the CIE illuminant C, and
29、not the full designation (C/2).INTERNATIONAL STANDARD ISO 22891:2013(E) ISO 2013 All rights reserved 1BS ISO 22891:2013ISO 22891:2013(E)3.3single-sheet luminance factor (C)R0luminance factor (C) of a single sheet of paper over a black cavity3.4white backing luminance factor (C)Rwluminance factor (C)
30、 of a white backing3.5intrinsic luminance factor (C)Rluminance factor (C) of a layer or pad of material thick enough to be opaque, i.e. such that increasing the thickness of the pad by doubling the number of sheets results in no change in the measured luminance factor3.6transmittanceratio of the tra
31、nsmitted radiant or luminous flux to the incident flux under given conditionsCIE Publication 17.4:1987, 845-04-593.7regular transmittancerratio of the regularly transmitted part of the (whole) transmitted flux to the incident fluxCIE Publication 17.4:1987, 845-04-613.8diffuse transmittancedratio of
32、the diffusely transmitted part of the (whole) transmitted flux to the incident fluxCIE Publication 17.4:1987, 845-04-63Note 1 to entry: = r+ d.3.9transparent mediummedium in which the transmission is mainly regular and which usually has a high regular transmittance in the spectral range of interestC
33、IE Publication 17.4:1987, 845-04-108Note 1 to entry: Objects may be seen distinctly through a medium, which is transparent in the visible region, if the geometric form of the medium is suitable.3.10translucent mediummedium which transmits visible radiation largely by diffuse transmissionCIE Publicat
34、ion 17.4:1987, 845-04-109Note 1 to entry: Objects are not seen distinctly through a translucent medium.2 ISO 2013 All rights reservedBS ISO 22891:2013ISO 22891:2013(E)3.11transmittance from reflectance factor measurementsTtransmittance obtained by direct measurement of luminance factor (C) (filter r
35、eflectometer) or determination of luminance factor (C) from measured reflectance factors (abridged spectrophotometer) and subsequent calculation as defined in this method4 PrincipleThe luminance factors of a single sheet of paper over a black cavity and over a white backing are determined by measure
36、ment according to standard procedures. The transmittance is calculated from the luminance factors.5 Apparatus5.1 Reflectometer, having the geometric, spectral and photometric characteristics described in ISO 2469, equipped for the measurement of the luminance factor, and calibrated in accordance wit
37、h the provisions of ISO 2469.5.2 Filter-function: in the case of a filter reflectometer, a filter that, in conjunction with the optical characteristics of the basic instrument, gives an overall response equivalent to the CIE tristimulus value Y of the CIE 1931 standard colourimetric system of the te
38、st piece evaluated for the CIE illuminant C.In the case of an abridged spectrophotometer, a function that permits calculation of the CIE tristimulus value Y of the CIE 1931 standard colourimetric system of the test piece evaluated for the CIE illuminant C using the weighting functions given in Annex
39、 A. The spectrophotometer should be fitted with a 420 nm UV cut-off filter for fluorescence elimination, as described in ISO 2469.5.3 Reference standards, issued by an ISO/TC 6 authorized laboratory in accordance with the provisions of ISO 2469 for calibration of the instrument and the working stand
40、ards. For maximum accuracy, reference standards having assigned values within the maximum range expected for the particular product to be tested should be selected.If there is reason to suspect that the instrument has poor linearity or that the deviations from the true colour matching and observer f
41、unctions are greater than can be tolerated, the use of product-specific reference standards should be considered.Use new reference standards sufficiently frequently to ensure that the reflectometer is maintained in agreement with the reference instrument.5.4 Two working standards, calibrated in the
42、apparatus concerned against ISO reference standards of level 3 supplied by an authorized laboratory (see ISO 2469). Calibrate the working standards sufficiently frequently to ensure that satisfactory calibration is maintained.5.5 Black cavity, for calibration or validation of the low end of the phot
43、ometric scale, and also for use as a black backing for some of the measurements. This black cavity shall have a radiance factor which does not differ from its nominal value by more than 0,2 percentage points at all wavelengths. The black cavity should be stored upside-down in a dust-free environment
44、 or with a protective cover. During calibration, the instrument shall be adjusted to the nominal value of the black cavity.It is not yet possible to institute a system of reference standards to enable testing laboratories to check the reflectance factor of the black cavity. At the time of delivery,
45、the level should be guaranteed by the instrument maker. Questions concerning the use and condition of the black cavity should be resolved by contacting the instrument maker.5.6 White backing, consisting of an opaque non-fluorescent white material with a flat, matt surface. ISO 2013 All rights reserv
46、ed 3BS ISO 22891:2013ISO 22891:2013(E)NOTE A pad of paper or a ceramic tile is suitable.6 SamplingIf the tests are being carried out to evaluate a lot, the sample should be selected in accordance with ISO 186. If the tests are carried out on another type of sample, make sure that the test pieces tak
47、en are representative of the sample received.7 Preparation of test piecesAvoiding watermarks, dirt, and obvious defects, cut at least five rectangular test pieces approximately 75 mm 150 mm. Place the test pieces between the protecting sheets.Mark the test pieces in one corner to identify the sample
48、 and its top side.If the top side can be distinguished from the wire side, it shall be uppermost; if not, as may be the case for papers manufactured on double-wire machines, ensure that the same side of the sheet is uppermost.8 Procedure8.1 If the test material contains or is suspected to contain a
49、fluorescent whitening agent, make sure that the fluorescence emission is eliminated by inserting the 420 nm UV cut-off filter (see 5.2) into the light beam, as indicated in ISO 2469.8.2 Using the procedure appropriate for the instrument in accordance with the manufacturers instructions, determine the luminance factor (C) of the white backing, Rw. Read and record the value to the nearest 0,01 % luminance factor (C).8.3 Without touching the test area, place the first test piece over the white backing and determine the lumi
