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THE IFRAO STANDARD SCALE (NOV. 2001)

The IFRAO (International Federation of Rock Art Organisations) Standard Scale was first proposed in IFRAO Report No. 6 (Bednarik 1991). Consultation of researchers and various specialists in the following years led to progressive evolution of the design (cf. Rock Art Research 8: 156) until it was finalised in 1993. The Australian Institute of Aboriginal and Torres Strait Islander Studies then made available a grant to meet the cost of producing the Scale, through its Rock Art Protection Program. The Institute realised the enormous advantages of such a measure – in documentation, computerisation, and the study of rock art and patination.Purpose of the Scale
We know that there are many millions of photographs and colour transparencies of rock art in existence worldwide: in my estimation at least twenty millions. Many archives have in the order of hundreds of thousands of images, while thousands of individual researchers each possess collections of many thousands of colour slides or photographs. We also know that this enormous collective record is irreplaceable, and yet it is doomed to eventual destruction.

No known photographic dye is fade-proof, and we still lack any form of permanent photographic or digitised storage of imagery (Dickman 1984). In short, this enormous effort of creating a visual record of world rock art is ultimately in vain. Even with rapid rock art deterioration it will be survived by most rock art, fortunately. But there is a simple way of rendering this massive record permanently useful: digitised colour reconstitution or reconstruction.

In scientific photography it is essential to know the size of an image, and for this purpose, Taylor et al. (1979) designed a simple ten-centimetre scale for rock art recording. A scale has other roles too. It serves as a general indication of a photograph”s sharpness, by showing how well it was focused and processed. Manual focusing is often difficult with rock art, because of the typical lack of straight or well-defined lines, and the operation of a camera with viewfinder focusing is much easier by selecting one of the lines on a scale.

More important than the black and white scale markings are the colour blots. The colour properties of An object are always distorted in a photograph, by such factors as optics, film type, paper type, temperature and, most particularly, lighting conditions. Therefore a colour photograph cannot be expected to be a true record of chroma, value and hue. However, by checking the colour distortion on a scale photographed with the rock art we can obtain an indication of its severity.

Some rock art researchers (a very tiny minority) have been using a variety of colour scales, including the Munsell Soil Colour Chart, the Kodak Colour Separation Guide, the Letraset Pantone colour chart and a variety of others. These colour standard charts are all expensive, they are all different, and standardisation would obviously be desirable.

The main reason for needing a standard photographic scale, however, is its function as a COLOUR CALIBRATION DEVICE for a variety of computer-supported uses. Electronic colour enhancement methods have been used in rock art studies for many years (Rip 1983). In 1994, electronic colour reconstitution of rock art images was achieved at the National Museum of Man in Bhopal, India, calibrated with the IFRAO Standard Scale as the profile device (Bednarik and Seshadri 1995). This has led to the development of colour-reconstitution software at the Museum.

The original colour values of colour-distorted and even faded rock art photographs can now be automatically reconstituted almost in an instant. The only precondition is that the photograph must bear a colour standard against which the computer can calibrate. The greatest advantage is that the computer does not recover the colour properties of the original photograph, before it faded, but goes beyond that – all the way back to the true colour of the rock art image at the moment it was photographed! It reconstitutes the actual colour properties of the subject at the time, even if this was several decades earlier. Colour reconstitution thus compensates for photographic distortion as well as for the subsequent fading of dyes.

This technology opens enormous possibilities in research, recording, documentation storage, computerised image manipulation, publishing and conservation studies. For instance, such techniques can facilitate mathematically precise monitoring of deterioration of rock art pigment or patinae over any period of time (Pager 1992; Ward and Maggs 1994; Bednarik 2002). They permit the recovery of objective colour information, free of the ”technical subjectivity” of conventional photography.

They facilitate the digitisation of real colour information, which can then be used in many ways: it can be permanently stored, it can be used as the basis of enhancement procedures (Rip 1989), or it can be cross-checked in intra- and inter-site studies for various purposes by engaging computer search functions.

Such information can also be used in conservation, retouch, graffiti and lacunae repair, comparative pigment studies, sourcing studies, dating work, recovery of very faint images, printing of colour plates and so forth.

It provides a reliable and standardised base for numerous applications, and while many of the technologies required might not yet have been developed, it is most reasonable to expect that they will be available within a few years. All that is required at this stage is that every photograph taken of rock art for scientific purposes must hear the same colour
calibration standard scale.

The long-term effect of the use of the IFRAO Standard Scale will be a standardisation of the photographic record of world rock art. Our archival record will become a permanent record by virtue of its retrievability. The greatest fear of all rock art studets, that the art will deteriorate beyond archival recovery, can be met by the knowledge that the susceptibility of our photographic record to colour calibration will lead to an ”ultimate conservation method”. We will have the means of preserving rock art in pristine condition forever, at least in our archives.

Use of the IFRAO Standard Scale
The IFRAO Standard Scale bears the printing date and will be periodically reprinted to guard against fading. It should be stored in a dark, dry and cool place when not in use. It includes a grey scale for comparing tone values. The patches correspond with reflection densities of 0.0, 0.70 and 1.60 respectively.

The Scale must never be placed over rock art, or very close to a motif. Preferably it should not be attached to the rock face. In vertical or overhead locations, the Scale should be hand held. Only where definitely undecorated and structurally sound rock surface is available may the use of small double-sided adhesive pads be considered, or the insertion of small metal pins through the Scale to affix it to soft rock surfaces (e.g. in limestone caves); but this is to be avoided whenever possible.

The Scale should be positioned parallel to the predominant plane of the rock art motif and the same distance from the camera lens. Ensure that the Scale does not directly reflect the lighting source. One Scale should be used for distances of up to 1.5 m. Between 1.5 and 4.5 m, two Scales are required. The Scale cannot be used with precision at distances exceeding 4.5 m, using lenses of standard focal length. Best results will be achieved at distances of under 1 m.

Where artificial lighting is required, place the Scale on upper left corner and light the image from the same direction. However, natural lighting is preferred to artificial. The small scale on the left-hand end of the IFRAO Scale is intended for close-up photographs. For best digital results, slides or negatives are preferred to prints.

The IFRAO Standard Scale is distributed free to all rock art researchers of the world (the members of the IFRAO-affiliated organisations). In addition, specialists in various other fields are rapidly adopting it. Specimens of the Scale are available from the IFRAO Convener”s office (P.O. Box 216, Caulfield South, Vic. 3162, Australia). The sale of the IFRAO Scale for profit is not permitted. The Scale is not subject to copyright within IFRAO and may be reproduced by any organisation affiliated with IFRAO – but again, not for profit.

Acknowledgments
I express my gratitude to the sponsor who underwrote the production costs of the IFRAO Standard Scale, the Australian Institute of Aboriginal and Torres Strait Islander Studies, Canberra, Australia. I also thank the Australia-India Council, Canberra, for supporting the work at the National Museum of Man in India in 1994.

(ROBERT BEDNARIK)

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