An Objective Colour-Measuring System

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gypt xploration Society

An Objective Colour-Measuring System for the Recording of Egyptian Tomb PaintingsAuthor(s): Nigel StrudwickSource: The Journal of Egyptian Archaeology, Vol. 77 (1991), pp. 43-56Published by: Egypt Exploration SocietyStable URL: http://www.jstor.org/stable/3821952.

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entirely satisfactory solutionoryolution to the problem of documenting the colours has yet to befound. In the days of Norman de Garis Davies, the most prolific and finest publisher ofthese tombs, it was normal to note the colours in the text by 'red', 'green', etc., often withcorresponding 'R' and 'G' on the drawings;4 in addition, Davies and his wife Ninaproduced superb colour facsimiles of many of the most beautiful scenes.5 The writing ofcolour abbreviations on drawings has largely fallen out of use, but colour facsimiles arestill in many ways the ideal means of publishing a painted tomb; unfortunately, it requiresan artist of unusual abilitybilityand makes a publication prohibitively expensive. The use ofcolour photography has become common in recent years, but standards of reproductionvary and there is often insufficient checking (by the publisher/printer) of the printedcolours against the original.6Colour charts have been employed for many years by archaeologists as a method forrecording the coloration of soils and ceramics. The first such use in Egyptology knownto me dates from the I930s, when the Ostwald Colour Album was employed to describethe colour of Predynastic sherds found in excavations at Armant.7 Today, the preferredmethod is the use of Munsell Soil Charts. It is only more recently, particularly withreference to the revival of interest inng Theban tombs since the 970os, thatcolour charts have begun to be used in epigraphy; the results, at least in terms of arecognition of the need for documentation, have been encouraging. The favouredstandard in use is the Munsell Book of Color.9However, there are two major problems with the use of colour charts, namely,inconsistency of the illuminant at different times of measurement in the same tomb, andinconsistency of the observer. To the latter should be addedthehenatural variation betweenindividual perceptions of colour. The consistency of the observer is not helped by thelaborious nature of working through a colour chart in order to find the best match, oftenin less than ideal circumstances; one tires very easily and it is easy for one's judgement tobe impaired.Having suffered these problems ourselves, I resolved to try and find an electronicmeasuring system, which should have the advantages of objectivity and consistency, andbe appropriate to the field environment; a necessary feature should be that it has its ownlight source so that all readings can be taken under the same circumstances. From thework of the Egyptian Antiquities Organization/Getty Conservation Institute (EAO/GCI)in the tomb of Nefertari, it became clear that such a device was made by the MinoltaCorporation; it is there being used successfully to document the deterioration of colour.10An approach was made to Minolta for assistance with our project, and a CR-22I colori-meter was made available to us on very favourable terms.4Such as Nina de Garis Davies, Scenes rom Some Theban Tombs(Oxford, 1963), pl. i.5For example, Nina de Garis Davies and Alan H. Gardiner, Ancient Egyptian Paintings, i-iI (Chicago,1936). 'See my comments in a review in JEA 74 (1988), 273-4. Cf. Caminos, op. cit. 12-13.7J.Scott Taylor in Sir Robert Mond and Oliver H. Myers, Cemeteries fArmant, i (London, 1937), 186-7.8Notably in the publications of the German Archaeological Institute, such as Artur und Annelise Brack,Das Grabdes Ilaremheb(Mainz, 1980) and Das GrabdesTjanuni (Mainz, 1977).In particular,Munsell Corporation, Book of Color:GlossyFinish Collection(Baltimore, 1976).10See F. Preusser and M. Schilling, 'Color Measurements', in Egyptian Antiquities Organization and theGetty Conservation Institute, Wall Paintingsfrom the Tombof Nefertari:ScientificStudies or theirConservation(Cairo/Los Angeles, 1987), 70-81; this paper will henceforth be referred to as Nefertari.It is important toemphasize that the EAO/GCI project is less concerned with absolute colour than with changes which maytake place over time. My work intends to document the present colours. [Since writing this paper, I havelearnt that a Minolta CR-200 was used to document the cleaning of the frescoes in the Sistine Chapel in theVatican.]

44 NIGEL STRUDWICK

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46 NIGELSTRUDWICK JEA77employ a look-up table. While it is possible to print measurements in all colour notationsone by one as they are taken, they are stored in the memory only in the one notation cur-rently chosen. An extra option I would like to see added to the instrument would be theabilityto convert stored readingsto any of the other notations,so that one could, forexample,printa listof readings irstly n Munsell andthenin Yxy notation.2. Useof theCR-22IThe instrument is very simple to use. It must first be calibrated using a white referencetile supplied with the unit. To maintain accuracy, it is advisable to recalibratetheinstrument requently.13he preferredcolour notationshould then be chosen,alongwithsetting the various indexes regarding printing, single/multiple measurement and so on. Asuitable area should then be selected for measurement and a 'measure' button pressed,eitherthat on the measuringheador thaton the dataprocessor.

The instrumentwas generallyvery straightforwardo use in the field. Batteries ast forbetween 200oo nd 300 readings, an adequate number for a day's work, particularly sincethe maximumcapacityof the memory is 300 readings.With simultaneousprintingofresults in all colour notations, one reading can be made every ten seconds or so; withoutprinting it is much faster. We printed in all notations, since it was desired to keep ascomplete a record of the measurements as possible and because the instrument can onlystore data in one colour notation. One minor difficulty is that the thermal printer has lowpaper traction and will only feed the paper through when the data processor is horizontal;it had been hoped to carry the processor vertically in a small shoulder bag leaving onehand free for other purposes, but in actuality the processor either had to be held in themeasurer's hand or placed on a table.An Apple Macintosh Plus computer was to be taken into the field for a variety ofpurposes during the season, and it was logical that the CR-22I be linked to it. Our onlytechnical problem arose when attempting to link the instrument to the computer, sincedespite wiring the cables in the conventional way according to the data supplied by themanufacturers, it was not possible to make the instruments communicate. After examina-tion of the port with an oscilloscope, it was found that the various pins of the RS232 porton the CR-22I needed to be wired in a somewhat unusual fashion. Specifically, the RTSand CTS pins are active high, whereas normally they would be expected to be low. Thediagram below shows that only two wires are necessary at the CR-22I end.14 Onceactivated, this link worked very successfully and saved a great deal of time. Data wastransferred into a text file which was then read into cards of a Hypercard stack. Noteswere then added to this database concerning the location and colour of the original.These notes were made in the field with a hand-held cassette tape recorder as a morerapid alternative to writing. Analysis of the data is being undertaken with the aid of thedatabase program Reflex Plus and the spreadsheet Wingz.

13The instrument's manual recommends recalibration at the beginning of each measuring session; I havetried to recalibrate when moving from one scene to another in the tombs, perhaps on average every twentyto thirty readings. For future work Nick Hale has recommended that the instrument be calibrated against areference tile visually close to each colour to be measured.14 I am indebted to Graham Louth (Statistical Laboratory, University of Cambridge) for his help in solvingthis particular problem.



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I991 AN OBJECTIVECOLOUR-MEASURING YSTEM 47TXD--GND - - _- @ 1 ? 8 @ 3

3. ModificationsThe design of the CR-22 I is such that the measuring unit is attached to a baseplate, thepurpose of which is to facilitate correct alignment of the measuring head with the sample.The opticalheadmust be at right-angles o the specimensurfaceso thatthe incident ightdoes not escape and sufficient light reflected from the colour reaches the sensors.However,the presenceof this baseplatecreates two problemswhenthe device is used ona tomb wall:(i) it is highly undesirable hatsuch a metalplatecome into direct contactwith the painted plaster or rock; (2) given that Egyptian tomb walls are usually far fromperfectly flat, the rather large baseplate sometimes prevents the measuring head being asclose to the subjectas one would like.Ideally, he baseplateshould be removed,butwiththe CR-22I this is not practical. The obvious solution to (i) is to provide a soft surface ofsome type between the baseplate and the wall. (2) can only be solved by careful selectionof subject areas, although it is to be hoped that Minolta will enable the baseplate to beremoved from future versions.A layer of transparent plastic acetate was used for the protective surface, a materialeasily available as it is the same as used for making facsimile drawings. Since providingthis protective surface for the wall increases the distance between subject and measuringhead, the optical conditions vary slightly from the design condition and somemeasurement error may result. I examined the effect of this on the CR-22 I before goinginto the field and found that the presence of the acetate does not have a serious effect onthe readings.15As reference colours, a British Standards Institution colour chart which wehad been using in the field before turning to the CR-22I was employed.16Readings weretaken on seventy-five randomly chosen colours, one without the padding and one with;the readings were made in Yxy colour spaces, so that any calculation of the differencescould be easily quantified. The following presents the results in the summary form of themaximum and minimum differences and also the standard deviation for the range ofvalues:

Y x yMax i.88 0.04 o.oIMin - 0.64 o.oo o.ooStandard deviation 0.40 o.o0 0.00

15A study of the effect of the addition of a protective cushion on the CR-I2I carried out by the GCIreached a similar conclusion. Their approach was different in that the baseplate of the CR-12I could beeasily removed, and a padding was only needed immediately around the measuring head (Nefertari, 70-2).The problems are, however, essentially the same.16Frameworkor colourco-ordination or buildingpurposes BS 5252: 1976).



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From these figures, it will be apparent that the difference is indeed minimal and cansafely be disregarded. Putting it in the visual terms of the Munsell Book of Color as givenby the CR-22 I, I give below three typical examples:

BookofColor CR-22I unmodified CR-22I modified5B 7/8 5.iB 7.0/7.4 5.oB7.0/7.4IoR 4/6 Io.oR4.0/6. I io.oR4.0/6. I2.5Y8/6 i.7Y 8.0/4.7 i.7Y 7.9/4.3

These measurements should be considered in the light of the following discussion ofthe relationship of the systems. However, it shows that the difference produced by themodification has an inconsequential effect on the Munsell colour space.

III. Systems and problems of colour measurementI think it is safe to say that, although the basis on which colour is being measured inEgyptological fieldwork is improving, Egyptologists have undertaken this work withoutreally understanding the basic theoretical issues and problems involved. We were equallyguilty in our first season in the field with the CR-22I. Of the available literature, theintroduction I would recommend to readers is Fred W. Billmeyer, Jr. and Max Saltzman,Principlesof ColorTechnology2New York, 1981 ).It is important to begin by understanding the component elements of what is calledcolour, whether it be seen by the human eye and brain or measured by an instrument.These elements are three in number: the light source under which the coloured object isviewed, the coloured object itself, and the response of the observer. These are moretechnically known respectively as the Spectral Power Distribution of the light source, theSpectral Reflectance of the object, and the Spectral Response of the observer. If thewavelengths of the three components are multiplied together, the resulting product (theperceived colour) can be termed the Stimulus for Colour.17Therefore, it can be seen thatthe variability of the light source and the observer can make crucial differences to theperceived colour, even with the same sample. Most readers of this paper will have had thedisconcerting experience of finding that two items, such as clothes, which match underartificiallight, do not match in daylight. This phenomenon is known as 'metamerism', andtwo such colours as a 'metameric pair', and is due to the fact that the spectral reflectanceof the two objects is different, but that he product of the calculation described abovehappens to be the same for a particular light source and observer.18Metamerism is apotential problem when colour charts are used to quantify colour. Even when using aninstrument with its implicit objectivity and consistency, the light source must remainconstant for the readings to have any meaning. The CR-22 I solves this by having its ownin-built source which is powerful enough to overcome the influence of the local lightsource.An extremely important issue is the question of the colour standard to be used whenreferring to colours in the publication, given the ability of the CR-22I to measure in a

17See the figure in Billmeyer and Saltzman, op. cit. I 7.Illustrated in ibid. 54-5, there using the calculation of CIE Tristimulus values. See ibid. 44-7 for anexplanation of this term and its calculation.

48 NIGELSTRUDWICK JEA77



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AN OBJECTIVECOLOUR-MEASURING YSTEMnumber of colour spaces. The instrument makes two types of colour space available,numerical and visual, the former being typified by the Yxy system (the base system of theCR-221) and the latter by the Munsell Book of Color.Eachhas its advantagesanddisadvantages,whichmaybe summarizedas follows:Numerical(Yxy)Advantages:

I. It is possibleto obtaina reading or all colours.2. For the same reason, it is possible to quantify arithmetically the difference betweencolours,and also to performstatistical alculations.193. In the present context, a numerical system lends itself to measurement byinstrument.

Disadvantages:i. It is impossible to illustrate the colour concerned without reference to a visualstandard, uch as Munsell.

Visual(Munsell)Advantages:

i. A rapidmethodforseeingwhat colourthe readingrepresents.2. The visual nature of the system is more accessible and perhaps more likely to gaininitialacceptance.

Disadvantages:I. It is impossible to represent visually all possible colours, since the colour chips inthe BookofColorarebuta subsetof allpossiblecolours.2. Spectralreflectancewas noted above as one of the three importantelements ofcolour. Therefore,it is only correct to compare a glossy colour, such as in the

Glossy Finish Edition of the Book of Color,the usual set of Munsell charts taken intothe field, with the rougher, more matte finish of tomb painting when the gloss isdeflected from the eyes ofheyes of the observer. Metamerism will also be a problem asoutlined above, especially since the Munsell charts are designed to be matchedusing the CIE (Commission nternationalede l'Eclairage) lluminant C, which approxi-mates to average north daylight, and CIE 2 degree Standard Observer;20neither ofthese is likely to be precisely what obtains in a Theban tomb.

3. It is difficult to relate the hue components except within the confines of the samechart, since although Munsell space is three-dimensional, and can be represented asa solid, the charts are two-dimensional, and show the value and chroma for a sethue.The choice between the two is difficult, since it seems that numerical systems areinherently more accurate, and yet visual systems are far more likely to gain acceptance in

19This is the purpose of the EAO/GCI investigation, where the variation of the colour is more importantthan the actual visual hue.20 These standards are explained in Billmeyer and Saltzman, op. cit. 34-44.

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the context of why an Egyptologist should want to study the colours of tomb paintings. Iwill describe in ?IV a solution which uses aspects of both.If the Munsell system is to be used with the CR-22 , it is necessary that users knowhow accurateent is relative tohise Book of Color. As pointed out above, theMunsell reading from the CR-22 I is made via a conversion process from the Yxy system.At the time of the first use of our instrument in the field, we had no independent informa-tion on the reliability of this conversion. However, since that time, I have learnt that theinstrument is not i 00 per cent accurate in this respect; the internal conversion from Yxyto Munsell is performed by looking up the values in a table, and certain corners havebeen cut to enable this process to be fitted into the storage of the CR-22i . As described atthe end of this section, I have now obtained corrected Munsell readings.However, the question of what degree of error is acceptable is a very important one forthe archaeologist. The instrument, and much of the colour technology being discussed, isemphatically not designed with the circumstances of the archaeologist in mind, but ratherfor colour measurement and matching under more ideal, almost laboratory, conditions.So many potential secondary factors are likely to creep in while in the field that aimingfor total accuracy is unfeasible, and thus, the innate error factor is, for our purposes, not amajor problem.To be able to make comparisons, we were most fortunate to have the loan of a copy ofthe Book of Color:GlossyFinish Collectionwhile in Luxor in late i988.21 The introductionto this publication should be consulted for an explanation of the Munsell system; it isassumed in this paper that readers are familiar with its basic tenets.Three sets of tests were carried out with the aid of this publication. Firstly, some CR-221 readings were made of the colour chips and then compared.22This showed that thereadings were, with some differences, substantially accurate. This view was subsequentlyconfirmed by Max Saltzman and Nick Hale, with the proviso, as noted above, that anyerrors innate to the machine would not really be significant given the less than ideal con-ditions in which the instrument was to be used.The second was in circumstances more relevant to our purpose, namely, a rather rapidinitial test in Theban tomb 178, with the cooperation of Eva Hoffmann of theAgyptologisches Institut Heidelberg. The results were compared with her estimationsfrom the Munsell Book of Color. The results were very variable, and the two followingexamples show typical difference and agreement.

BookofColor CR-22 ColourioBG 6/4 i.gBG 6.3/2.0 Turquoise2.5YR 7/6 2.7YR 6.8/4.3 Pink

This variability can be partly attributed to the unavoidable rapidity with which this testwas carried out, but there are also two other important factors. Firstly, some of thecolours are faded or dirty. Although the human eye and brain may take much longer than

211I am indebted to Karl Seyfried, Field Director of the University of Heidelberg 'RamessidischerBeamtengraber in Theben' project for the loan.22 t should be pointed out that the chips in the Book of Color are the closest possible approximation to thecolour described within the tolerances accorded that publication at the time it was produced. By the time thebook has been in use for a few years the chips may have changed slightly. None of this is critical to thepractical use in the field where tolerances are large, but theoretically it is of the highest importance.

NIGEL STRUDWICK JEA 770



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AN OBJECTIVECOLOUR-MEASURING YSTEMan instrument o make readings,and be much less consistent,it can more easily take asample on a much smaller area than the CR-22 I.23Secondly, the angle of measurement iscritical. The CR-22I, being designed more for laboratory conditions than anything else,has problemswith an uneven surface.The abovereadingswere made with the baseplatein place, the purpose of which is to ensure that the head is held at the correctperpendicular angle to the sample; given the large size of the baseplate, it is possible foran uneven surface to distance the sample from the wall slightly (as with the protectivemodification, ee ?11.3), r to changethe measuringangle.The important lesson learnt from this test was clearly that it is necessary to select one'ssample with great care, choosing an area that is sufficiently large, clean and level. Thiswas applied in our third and major test of the instrument, in the tombs which I ampublishing.The tomb of Amenmose(TT 254) is the bestpreservedof the three,and alsohas the freshest colours. We hoped that it would thus be a good test of the CR-221.We beganby takinga numberof readingsandcomparingeachwith ouropinionof thecolour by use of the Bookof Color.Areas were selectedfollowingthe criteriadiscussedabove. An initialroundingup or down was made of the readingto the nearestBookofColorchip,whichwas thencomparedwiththewall,underlightingconditionswhichwerea combinationof daylightand tungstenbulbs.We workedfrom this firstapproximationuntil the best Munsell match was found. It will be seen that the CR-22I was usuallyextremelyclose to the readingdecidedvisuallywiththe BookofColor,although his is notreally an unbiased test, in that our Book of Color starting point was defined for us. Tentypical results are given below:

Reading Colour and subjectI Yellow-Background to text onborder of stela2 Green-Face of god Osiris3 Blue-Blue areaon thethroneofgod Osiris4 White-White crown of godOsiris5 Red-brown-Stomach ofAmenmose6 Pink-White kilt overthe red

legs of Amenmose7 Yellow-brown-Roundloavesamong offerings8 Yellow(verylight)-Femaleskincolour9 Green-Block border to right ofstelaIo Red (dark)-Pot held up byserving woman

Book fColorMunsell romCR-22 I in thefield

ioYR 7/6 8.3YR7.o/6.27.5G 6/27.5B 6/2IoYR 9/ IioR6/6

7.2G 6.3/I.57.IB 6.3/1.99.3YR 8.9/ .io.9YR5-7/5.5

2.5YR 7/4 2.2YR 7.3/3.85YR6/6 4.7YR 6.3/6.5ioYR 8/4 9.IYR 7.8/3.25GY 8/2ioR 5/6

5.iGY 7.2/2.28.4R 4.7/6. I

More accurateMunsell8.57YR 6.95/6.327.24G 6.19/1.477.-iB 6.22/2. I08.87YR 8.86/i. I II.I IYR 5.63/5.692.43YR 7.23/4.084.84YR 6.26/6.779.o9YR 7.74/3.245.o2GY 7.14/ I.998.42R 4.70/6. IO

23Orrather, t thinks t can take such a measurement.The humanobservermerelybelieveshe can,but isliableto be heavilyinfluencedby the surrounding olours.Therefore,his resultis almostcertainlygoing tomoreinaccuratehan the 'objective' eadingof the instrument,whatever heproblems nvolved n measuring.Likewise, the observer may think he can make allowances for the dirt on a colour sample when choosing hischip, but this is again improbable.

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It was indicated above that the internal conversion of the CR-22I from its native Yxyreadings to Munsell was slightly inaccurate. The original Yxy data has been converted tomore accurate Munsell readings using a computer program developed at TeesidePolytechnic:24this data is presented in the fourth column above.Overall the results are very satisfactory, provided suitable care is taken in choosing thelocations for the readings. After these initial tests, a total of 273 readings was made. The

CR-22I was recalibrated regularly, and periodic comparisons were made with the Bookof Color. The accuracy remained good, only certain colours showing occasionaldifferences. These were most noticeably blues and greens; the former may perhaps beattributed to the tendency of Egyptian blues to discolour and decay.The tests just described were performed purely for our own satisfaction as to theinstrument's behaviour. Given the likely variability of the human observer, the lightsource and the problem outlined above with regard to the different reflectivecharacteristics of the tomb walls and the Book of Color,there is very little objective valuein these comparisons, but we hope that they will help to convince Egyptologists of thetrustworthiness of the CR-22 I.

IV. Presentation and evaluation of resultsIn the course of our 1988-9 and 1989-go90easons a total of 360 measurements was madeof the colours in the group of tombs under study. Much thought has subsequently beengiven to how the results should be presented in the publication and to possible analysesof the data. The former is the more important at the present moment, since theproduction of adequate documentation of the tombs is our primary concern.The two principal systems of measurement for our purposes are the Munsell and Yxycolour spaces, and the data was recorded using both systems; the advantages anddisadvantages of both have been discussed in ?III.Because of the requirement to be ableto compare our readings with other published accounts, which use the Munsell system, itseems desirable to present the basic data in that format. The first problem is whether ourreadings should be corrected to the nearest colour chips in the Book of Color.As noted,that publication can only represent i ,500 or so of the millions of colours which can bedistinguished by the human eye, and it will have already beenlreadybeen apparent to the reader thatour readings fall between those neat divisions. Correcting the hue and chroma to thenearest whole values is visually not difficult,particularly since they appear on the samepage of the Book of Color,but attempting to interpolate the hue, except in the context ofthe colour solid, is not so easy. Also, too direct a comparison with the Book of Colormakes no allowance for the different reflective characteristics of those colours and thosein the tombs. It was thus decided to leave the CR-22I readings (corrected as described in?111) s they stand, permitting readers to make their own approximations.How should the data be arranged?There are two basic possibilities-arrangement bylocation or grouping by colour. Given the need to be able to find quickly the colour of aparticular item in the visual documentation of the paintings, it seems that arrangement by

24These programs have been developed by T. W. A. Whitfield and Neville S. Smith, and I am indebted tothem for making these conversions for me. A detailed description of the program has been published inColorResearchandApplication(December, 1990).

NIGEL STRUDWICK EA 772



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I99I AN OBJECTIVECOLOUR-MEASURING YSTEM 53location, wall by wall, tomb by tomb, is the best, and it is my intention, publisherpermitting, to give a list of the 360 measurements.It is important, nonetheless, to be able to group together readings of like colour so thatthe range of colour can be realized. Immediately, the problem of how to define verballythe general coloration of a sample arises. The subjectivity of individual descriptions hasalready been alluded to above; in the context of Egyptian wall-paintings, one person's'dark red' is another's 'red-brown'. There are several ways in which this difficulty may behandled, of which I shall consider three. In all cases, detailed discussion of the results willbe reserved for the final publication.i. Categoriesof objectsThe coloration of similar categorites of objects can be studied: good examples of thiswould be comparison of the male or female skin colours, each of which might beexpected to be reasonably consistent.There will, of course, be some variation within the Munsell readings assigned to aparticular object category. This is not easy to visualize except within the context of theMunsell colour solid, and very difficult to quantify, since the Munsell system, beingprincipally visual, does not lend itself easily to other methods of representation. This iswhere the readings in the Yxy system become useful, in that colour, as described in theCIE system from which the Yxy notation is derived, can be plotted on a two-dimensionalgraph or chromaticity diagram using the x and y components of that notation.25Chromaticity diagrams are a very good way of visually representing the spread of anyparticular grouping of colour readings. By plotting two or more sets of values on one

+ TT253 A Tr2540.3800 ~ A

_ A0.3700- A

-'A ^ A_4- A AY- A A A

0.3500 A A A A

+ A + +0.3400- A- +

0.3300 I i i I 1 I i T l i i i l l i i i l l l ' ' ' l l 10.3400 0.3600 0.3800 0.4000 0.4200 0.4400 0.4600 0.4800

xFIG.I. Chromaticity diagram of readings of the male skin colour in TT 253 and 254.

For more detail see Billmeyer and Saltzman, op. cit., in particular 47-52. The spread of the names of theprincipal colour divisions over a chromaticity diagram is illustrated in the figure on their p. 50.



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54 NIGELSTRUDWICK JEA77graph it is possible to compare how the same groupings of data vary between tombs. Forexample, fig. i shows the distribution of the measurements of male skin colour from bothTT 253 and TT 254. More detailed discussion of the implications of this will be reservedfor the published report of these tombs, although it will be immediatelyclear thatalthoughthere is quite a wide degree of variation n the same tomb, the two chapelsareusing distinctlysimilarversions of the sameintendedcolour.2. Systematic seofcolournamesThe very wide range of Munsell colours can be reduced by the use of a systematicallyorganized range of colour names. On the advice of Max Saltzman, I have used the schemeput forward by Kelly and Judd in their I976 National Bureau of Standards(NBS)publicationColor:UniversalLanguage ndDictionary f Names,specificallythe chartsonpp. I5-34.26In this publication,the Munsell colour space is divided into 267 colours,named according to a fixed set of conventions. Munsell colours can be given theirappropriate olourname eitherby using the charts,or else by the use of a purpose-builtcomputer program.For example,the NBS colour name 'greyishreddishorange'coversMunsell readings in the hue range 8. iR-3YR and the value/chroma range 4.59/5.29-6.37/5.85, and also the following ten verbal descriptions given by myself at the timeof takingmeasurements:

Brown Red (dark)Pale reddish-brown Red-brownRed Red-pinkBrownish-red Reddish-brownPink Yellow-brownThis variationcanbe illustratedby the chromaticitydiagram n fig.2.

+ TT253 A TT2540.3800 -

0.3700 - A.3 A0 iA

0.3600- A AA A

0.3500 - :A+- A + + A0.3400- A + +0.3300 1 1 T I i I I I I I I Ii I, , [, [ [ [ , , [ , '1

0.3900 0.4000 0.410O 0.4200 0.4300 0.4400 0.4500 0.4600 0.4700x

FIG.2. Chromaticity iagramof NBS colour'greyishreddishorange' n TT 253 and254.26Six levels intowhichcolours canbe groupedare summarizedn the table n BillmeyerandSaltzman, p.cit. 32.



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AN OBJECTIVECOLOUR-MEASURING YSTEMThis method has a disadvantage insofar as fine differences between colours can beobscured in the grouping. This might be a serious objection when working under ideal(laboratory) onditions,but given thatsome inaccuracycan creepin when working n thefield (as describedabove), such groupingcan actuallyhave the advantageof permitting

some leeway in the observations and preventing one from becoming convinced by whatmaybe a misleadingdegreeof accuracy.In connectionwiththese figures,the readermaywish to see how the rangeof readingsused for fig. i were describedat the time of recording(column i in tablebelow) and intermsof the NBS standardcolours(column2):ColourdescriptionBrownishredPink

Pinkish-redRedRed-brown

Red-brown

Yellowred-brown

NBS colournameGreyishreddishorangeGreyishyellowishpinkLightreddishbrownModerateyellowish pinkModerateyellowishpinkGreyishreddishorangeModeratereddishorangeBrownishorangeGreyishreddishorangeGreyishreddishorange/LightbrownGreyishreddishorange/Moderate eddishorangeLightbrownLightreddishbrownModeratereddishbrownModeratereddishbrown/LightreddishbrownModeratereddishorangeModerateyellowishpinkLightbrown

Both tables illustrate the variability of one's terminology when faced with colours in atomb, although it does also show the range of shades of colour which can be disguised byone standardized term. Then again, the first table effectively reveals a bias in theobserver-for the most part the male skin colour is characterized by Egyptologists as areddish-brown, and thus that is the colour noted by myself when taking a reading on anormal example. Yet, as can be seen from the selection of colour names corresponding to'red-brown' above, there is far more variation in the male skin colour than the observerrealizes without reference to some more objective method.3. General spectsThe colours can be referred to in the broadest terms, such as the five basic hues of theMunsell system: red, yellow, green, blue, and purple. More relevant to Theban tombsmight be a division using the broad divisions of the New Kingdom palette, defined mostrecently by Baines as black, white, red, green, yellow, strong blue, light blue, grey, brown,and pink.27 This method has the disadvantage of adding an element of subjectivity,insofar as it is necessary to make visual and verbal classifications of even these broad

27AmericanAnthropologist87 (1985), 287.

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PLATE IVLATE IV

I. The Minolta CR-22I Colourimeter(courtesyofMinolta (UK) Ltd.)AN OBJECTIVE COLOUR-MEASURING SYSTEM (pp. 43-56)

I. The Minolta CR-22I Colourimeter(courtesyofMinolta (UK) Ltd.)AN OBJECTIVE COLOUR-MEASURING SYSTEM (pp. 43-56)

2. P. BM 0o40I. P. BM 0o40IREQUISITIONS FROM UPPER EGYPTIAN TEMPLES (pp. 79-94)EQUISITIONS FROM UPPER EGYPTIAN TEMPLES (pp. 79-94)

Documents

An Objective Colour-Measuring System