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1、ApprovedAmerican NationalStandardANSI/I3A IT2.40-2003for Photography Root Mean Square (rms) Granularity of Film (Images on One Side Only) Method for MeasuringANSI/I3AIT2.40-2003ANSI/I3A IT2.40-2003American National Standardfor Photography Root Mean Square (rms) Granularity of Film(Images on One Side

2、 Only) Method for MeasuringSecretariatInternational Imaging Industry Association, Inc. (I3A)Approved January 22, 2003 American National Standards Institute, Inc.Approval of an American National Standard requires review by ANSI that therequirements for due process, consensus, and other criteria for a

3、pproval havebeen met by the standards developer.Consensus is established when, in the judgement of the ANSI Board ofStandards Review, substantial agreement has been reached by directly andmaterially affected interests. Substantial agreement means much more thana simple majority, but not necessarily

4、unanimity. Consensus requires that allviews and objections be considered, and that a concerted effort be madetowards their resolution.The use of American National Standards is completely voluntary; theirexistence does not in any respect preclude anyone, whether he has approvedthe standards or not, f

5、rom manufacturing, marketing, purchasing, or usingproducts, processes, or procedures not conforming to the standards.The American National Standards Institute does not develop standards andwill in no circumstances give an interpretation of any American NationalStandard. Moreover, no person shall hav

6、e the right or authority to issue aninterpretation of an American National Standard in the name of the AmericanNational Standards Institute. Requests for interpretations should beaddressed to the secretariat or sponsor whose name appears on the titlepage of this standard.CAUTION NOTICE: This America

7、n National Standard may be revised orwithdrawn at any time. The procedures of the American National StandardsInstitute require that action be taken periodically to reaffirm, revise, orwithdraw this standard. Purchasers of American National Standards mayreceive current information on all standards by

8、 calling or writing the AmericanNational Standards Institute.American National StandardPublished byAmerican National Standards Institute, Inc.25 West 43rd Street, New York, NY 10036Copyright 2003 by American National Standards Institute, Inc.All rights reserved.No part of this publication may be rep

9、roduced in anyform, in an electronic retrieval system or otherwise,without prior written permission of the publisher.Printed in the United States of AmericaiContentsPageForeword ii1 Scope . 12 Normative references . 13 Definitions. 24 Microdensitometer 35 Electronics of the microdensitometer . 66 Pr

10、eparation of specimens. 77 Operation of the scanner 78 American National Standard diffuse granularity values 9Figure1 A typical microdensitometer . 3AnnexesA Conversion from projection to diffuse density. 11B Spectral conditions . 12C Circuit for measuring (D) 13D Microdensity calibration film . 14E

11、 Bibliography 15iiForeword (This foreword is not part of American National Standard ANSI/I3A IT2.40-2003.)This standard describes procedures for measuring the root-mean-square (rms) gran-ularity of photographic films. Its purpose is to provide guidance in the making of ac-curate measurements and als

12、o to provide a common basis of measurement so thatmaterials can be compared.In principle, the measurement of rms-granularity is straightforward, but its determina-tion with accuracy and precision is decidedly not a trivial matter. A large part of thetext deals with procedures intended to reduce the

13、influence of artifacts on the dataobtained and to decrease variability.Several allied kinds of granularity measurements have been excluded from this stan-dard, although they are photographically important. These are:1) rms-granularity of reflecting materials (papers);2) rms-granularity of materials

14、having emulsion coated on both sides of the sup-port (some x-ray films);3) measurement of the Wiener spectrum of photographic materials.In all of these cases, it was the feeling of the committee that insufficient experienceand data had been accumulated to justify preparation of standards covering th

15、emand that any attempt to do so would delay publication of this standard. Perhaps ex-perience with this standard will be helpful in preparing similar ones covering theseother cases.Suggestions for improvement of this standard will be welcome. They should be sentto the International Imaging Industry

16、Association, Inc. (I3A) , 550 Mamaroneck Ave-nue, Suite 307, Harrison, NY 10528-1615, e-mail: i3astdsi3a.org.This standard was processed and approved for submittal to ANSI by AccreditedStandards Committee on Image Evaluation. Committee approval of the standarddoes not necessarily imply that all comm

17、ittee members voted for its approval. At thetime it approved this standard, the IT2 Committee had the following members:Philip Wychorski, ChairmanJack Holm, Vice-ChairmanPaul J. Kane, SecretaryOrganization Represented Name of RepresentativeInternational Imaging Industry Association, Inc. (I3A) . Phi

18、lip WychorskiPhillip C. Bunch (Alt.)Paul J. Kane (Alt.)Thomas W. McKeehan (Alt.)Robert A. UzenoffRobert D. WhittallCGATS . Larry SteelePhotographic Society of America . Jack HolmIra Current (Alt.)US Dept. of Commerce National Institute of Standards and Technology Ted EarlyAMERICAN NATIONAL STANDARD

19、ANSI/I3A IT2.40-20031 American National Standard for Photography Root Mean Square (rms) Granularity of Film (Images on One Side Only) Method for Measuring 1 Scope This standard describes a method for the determination of the granularity of photographic films by scanning with a suitable microdensitom

20、eter. Continuous-tone black-and-white and color materials coated on a transmitting support may be measured by the procedures described. The concept of granularity applies to both reflecting and transmitting materials, and techniques that are basically similar to those described in this document can

21、be used to evaluate reflection materials. However, this document is concerned only with samples coated on transmitting supports. As noted in the Foreword, two other types of granularity measurements are not treated in this document. First, no specifications are given for measuring films that have em

22、ulsion coated on both sides of the support. Second, this document does not treat the measurement of the Wiener (or “power”) spectrum. 2 Normative references 2.1 Referenced International Standards The following standards contain provisions that, through reference in this text, constitute provisions o

23、f this American National Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this American National Standard are encouraged to investigate the possibility of applying the most recent editions of the standa

24、rd indicated below. Members of the IEC and ISO maintain registers of currently valid international Standards. ISO 5-1:1984 (R1989), Photography Density measurements Part 1: Terms, symbols and notations ISO 5-2:2001, Photography Density Measurements Part 2: Geometric conditions for transmission densi

25、ty ISO 5-3:1995, Photography Density Measurements Part 3: Spectral conditions 2.2 Other referenced publications 1 James, T.H., Ed. The Theory of the Photographic Process. 4th ed. New York: Macmillan; 1977: 618-628. 2 Trabka, E.A. Relationship between RMS density and transmittance fluctuations of pho

26、tographic film. Journal of the Optical Society of America. 59(5): 662-663; 1969 May. 3 Zwick, D.M.; Brothers, D.L. RMS granularity: Determination of just-noticeable differences. Photographic Science and Engineering. 19(4): 235-238; 1975. 4 Zweig, H.J. Autocorrelation and granularity: Part II Results

27、 on flashed black and white emulsions. Journal of the Optical Society of America. 46(10): 812-820: 1956 October. 5 Kaufman, M.; Seidman, A.H., Eds. Handbook for Electronics Engineering Technicians. New York: McGraw-Hill; 1976: Chapter 11. ANSI/I3A IT2.40-2003 2 3 Definitions 3.1 Transmittance factor

28、 and transmission density Transmittance factor and transmission density are defined in accordance with ISO 5-2:2001. The terms, symbols, and notations for optical transmission measurements set forth in ISO 5-1:1984 (R1989) shall be used in describing the density measurements made in connection with

29、granularity. It should be noted that most microdensitometers measure a form of density that is neither diffuse nor specular because in most such instruments the influx and efflux beams are formed by lenses having finite apertures, and the beams therefore subtend intermediate cone angles at the speci

30、men. Density values measured under such optical conditions are termed “projection” densities and are discussed in ISO 5-2:2001. (However, the lens apertures used in microdensitometry generally differ from the ones recommended in ISO 5-2:2001.) If the granularity values measured in accordance with th

31、is standard are in terms of projection density, they should be converted to diffuse density for reporting. A method for converting the values is given in Appendix A. 3.2 Microtransmittance factor and microdensity Microtransmittance factor is the transmittance factor of a small area of the film or pl

32、ate measured in a suitable instrument such as a microphotometer. In general, the microtransmittance factor of a “uniformly exposed and developed” film sample varies from point to point on the surface. The measured microtransmittance factor of a given film or plate may depend on the instrument in whi

33、ch it is measured. Microdensity is the transform of the microtransmittance factor in accordance with the usual relation: D = log10T. 3.3 Graininess Graininess is defined as the sensation produced in the mind of an observer viewing a photographic image by random inhomogeneity in what should be struct

34、ureless areas. Graininess is therefore a subjective quantity that must be measured by psychophysical methods. As such, it is outside the scope of this standard; however, the methods of measuring film granularity described in 3.3 have been found to give values which generally correlate with the magni

35、tude of the graininess sensation produced when the film is viewed under suitable conditions. 3.4 Granularity Granularity is defined as the characterization of the spatial variation in the transmitting or reflecting properties of a uniformly exposed and developed photographic layer 1).1)As noted in S

36、ection 1, only the transmitting case is considered in this document. The spatial variation is observed when the transmittance factor of the layer is measured at various points over the surface, and is the result of the random distribution of the attenuating structure in the layer. Granularity is the

37、refore an objective quantity. The variation in the transmittance factor over an area of the specimen is characterized by its standard deviation, (T). This quantity is termed the “rms-transmission granularity.“ It is calculated in the usual manner, i.e., where Txis the transmittance factor of the lay

38、er at the point x; T is the mean transmittance factor of the layer; n is the number of points at which measurements are made. _ 1)Numbers in brackets refer to corresponding numbers in 2.2. 2121)()(=nTTTxANSI/I3A IT2.40-2003 3 In practical work, data in terms of optical density are usually preferred

39、to transmittance data. For the purposes of this standard, the standard deviation of the transmission density is formally defined by the relation: The unqualified term “rms-granularity” may be applied to (D). If not made clear by the context of the measurements, a subscript T may be added to the D to

40、 indicate that transmission density is involved. The quantity (D) can also be calculated directly from a population of values of Dx, the microdensity at the point x, using the usual equation for standard deviation (see previous equation for “rms transmission granularity”). Mathematically, this proce

41、dure is questionable because Dxis a logarithm. However, it has been shown 2 that the differences between values derived from density and transmittance data are usually less than the errors due to other sources of variability with practical samples. Therefore, the calculation of (D) may be carried ou

42、t in terms of either quantity. 3.5 Specimen The term “specimen” will be used hereafter in this document to indicate the piece of film or plate on which measurements of rms-granularity are made. 4 Microdensitometer 4.1 Design of the microdensitometer The basic design of a microdensitometer for the me

43、asurement of granularity is described in this section. Microdensitometers of different designs may be employed, provided they are shown to produce values not significantly different (i.e., within 5%) from those that would be produced if the specimen were scanned on the instrument described. Influx A

44、pertureLightSourceCondenserLensInfluxOpticsEmulsion SideEffluxOpticsCollectingLensMeasuringAperturePhotodetectorSpecimenABCD E F G HIFigure 1 - A typical microdensitometer A typical microdensitometer is shown schematically in Figure 1. With reference to Figure 1, the various elements are as follows:

45、 NOTE - Letters after each element refer to corresponding letters in Figure 1. 1) Light source (A). 2) Lamp condenser (B). This lens focuses an image of the source on the entrance pupil of lens (D). TTD)(434.0)( =ANSI/I3A IT2.40-2003 4 3) Influx aperture (C). In the optical system shown, this apertu

46、re limits the area of the specimen that is illuminated in order to minimize stray light in the optical system. 4) Influx optics (D), which images the influx aperture (C) on the specimen (E). 5) Specimen (emulsion facing the efflux objectives) (E). 6) Efflux optics (F), which collects the light trans

47、mitted by the specimen and focuses it upon the efflux aperture of the instrument. 7) Efflux (measuring) aperture (G). This aperture, projected back onto the specimen, determines the area of the specimen whose transmittance factor is being measured. Its effective size at the specimen is determined by

48、 its physical size divided by the optical magnification from plane (E) to plane (G). 8) Collecting lens (H). This lens collects the light transmitted by the measuring aperture (G) and relays it to the photodetector. It is omitted in some designs. 9) Photodetector (I). 4.2 Influx spectrum Incident fl

49、ux for granularity measurements shall be that specified for normal densitometry in ISO 5-3:1995. For transmission density, it states that the relative spectral power distribution of the incident flux shall be that of the CIE Illuminant A modified in the infrared region to protect the specimens and optical elements. This is denoted as “SH.” 4.3 Influx aperture The influx aperture shall be approximately circular in shape, and its image shall be concentric with that of the efflux (measuring) aperture. When both apertures are r