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Commentary of 1987 
Shape and nature
    [p.1173] Annex I, Article 3 -- Shape and nature

    [p.1174] General remarks

    4031 The distinctive emblems reproduced in figure 2 are those of the 1949 Conventions. As pointed out earlier, the red lion and sun has not been used since 1980.

    4032 However, this emblem could only be deleted from the Protocol if the amendment procedure were followed.

    4033 The red cross and the red crescent should always stand out on a white ground. There are no provisions governing the shape and size of the white ground, which may be the hull of a hospital ship, the fuselage of a medical aircraft, or a white wall. It is not mandatory for medical aircraft or ambulances to be painted white. They often are, however, for the colour white is a thermal insulant.

    4034 There are no mandatory provisions regarding the size or proportions of the distinctive emblem. It is thus possible, in an emergency, to fashion the emblem using whatever materials are available. For the same reasons, the red and white colours are not standardized and may therefore be produced by improvisation if necessary.

    4035 Article 43 of the Second Convention refers to the colour dark red in respect of the distinctive emblems placed on hospital ships and coastal rescue craft. This is only a recommendation intended to secure a good red and white colour contrast. (1) Under Article 38 of the first Convention, the heraldic emblem of the red cross on a white ground is formed, as a compliment to Switzerland, by reversing the federal colours. The red colour of the Swiss emblem has been regulated and is quite dark; however, Article 38 contains no stipulations regarding either the shape or the colour of the distinctive sign, which retains its full protective value whatever the shade of the red and the white colours, as explained in a technical note published in the International Review of the Red Cross. (2)

    4036 When references are made to the size of the distinctive emblem,what is meant is its height and its width together with the area delimited by its contours. The distance at which it is visible depends on all these factors, or, in other words, on its red area. Comparative observations made during visibility tests by night and by day showed quite clearly that both a sign consisting only of lines and the surface of a crescent are less visible than an outspread cross of the same size.

    Paragraph 1

    4037 The expression "shall be as large as appropriate under the circumstances" represents a compromise between the need to ensure that the distinctive emblem is as effective as possible thanks to its size, and military requirements which, in some situations, call for the emblem to be camouflaged or made smaller.

    [p.1175] 4038 The visibility tests carried out on the distinctive emblem showed that the outline of a vehicle approaching from a distance can be seen before its colours are visible to the naked eye. If the red emblem on a white ground is supposed to be "as large as possible", it should be displayed over the vehicle's full height so that it can be identified on the outline as soon as the red and white colour contrast revealing it starts to appear. The same applies for aircraft, ships and small craft marked with the distinctive emblem.

    4039 Figure 2 gives an idea of the shape and proportions of the distinctive emblems and could be used as the basis for improvising one. More detailed information on the manufacture of distinctive emblems has been published by the ICRC in a trilingual booklet, which describes a method proposed by a National Red Crescent Society for the geometrical construction of the crescent. The Conventions lay down no rules for either the positioning of the red crescent on the
    white ground or its proportions. (3)

    Paragraph 2

    4040 The decision to light or illuminate the distinctive emblem is for the competent authority to take if it deems that the emblem should be identifiable at night or when visibility is poor.

    4041 The emblem is "lighted" by a projector or a lamp; the white light projected onto it brings out its shape and colours.

    4042 The emblem is "illuminated" when red and white lights are placed on it in order to pick out the red emblem against the white ground. This may be done by placing strings of red electric bulbs along the contour of the emblem and white bulbs round the edge of the white ground.

    4043 Furthermore, there is no reason why the emblem itself should not be luminous, giving off a red light surrounded by a white halo or glow. (4) This type of device, which could be based on those used for road signs and neon advertising signs, should be subjected to visibility tests.

    4044 The technical means of detection referred to in paragraph 2 are essentially those involving infrared (IR) observations, which may be divided into three categories;

    -- active electro-optic infrared observation, involving the emission of infrared light and the reception of reflected images;
    -- infrared photography;
    -- passive electro-optic infrared observation, involving the detection of infrared radiation from sources of heat.

    [p.1176] At the time of the Conference of Government Experts (1971-1972) such infrared observation methods were in general use in the armed forces, having been introduced during the Second World War. Other technical means of detection which were then starting to become known to the public at large, such as seismic or chemical "sensors" released by aircraft over vast areas and transmitting information by means of automatic radio signals, did not enable medical personnel, units and transports to be identified. The shortage of detailed documentation on this new "generation" of technical means of detection has prevented an accurate assessment from being made of their implications for the respect and protection to which medical services are entitled.

    4045 The ICRC tests carried out in 1972 and 1976 on the use of infrared observation to detect the distinctive emblem by night were confined to active electro-optic infrared observation using a projector and an image enlarger with screen. The wavelengths used for the infrared radiations ranged from 0.8 to 2.0 micron. (5) The
    observational distance was fairly short since it did not exceed 800 metres.

    4046 Following the communication to the ICRC by the Spanish Red Cross of photographs of ambulances taken with infrared sensitive film, on which the red cross could not be seen at all, infrared photographic tests prepared by the ICRC were also carried out. It will be recalled that infrared photography, both in black and white and in colour, is used under a variety of techniques for the day-time observation and aerial monitoring of combat and supply zones. The wavelength used for these tests ranged from 0.7 to 0.85 microns.

    4047 The ICRC did not test the visibility of the distinctive emblem by means of calorimetric electro-optic passive sensors, which may be used by both day and night for infrared passive observation of the differences in temperature caused by hot engines, chimneys, human beings, animals etc., in combat and supply zones. This type of passive electro-optical infrared observation using wavelengths from 3 to 5 and from 10 to 14 microns may be carried out from the air at altitudes of up to 3,000 metres.

    4048 The ICRC tests showed that the distinctive emblem is visible to active electro-optic infrared observation only through the colour contrast produced by the dark against a pale ground. The white ground reflects more than 80% of infrared light whereas the colour red reflects only 0 to 10%. If the colour red itself is placed on a pale ground, the contrast disappears. This holds good for photography too. When black and white infrared film is used with an orange filter, the emblem appears as a dark shape on a pale gray ground, if ordinary paint is used for the red and white colours. The contrast is improved if reflectorized material is used for the white ground and glossy
    paint for the red emblem.

    4049 Using a colour infrared film and a yellow filter, the emblem is seen as yellow on a reddish-gray ground.

    [p.1177] 4050 Various methods of improving the contrast were tested:

    -- a black band round the perimeter of the sign;
    -- a strip of reflectorized plastic material round the perimeter of the sign;
    -- red reflectorized hatching across the sign;
    -- addition of black pigment to the red paint;
    -- a black coating beneath the red.

    The last method was found to be the most effective in improving the dark-on-pale contrast, whereas the others made the shape of the cross stand out more clearly on its pale ground.

    4051 The ICRC was informed that the distinctive emblem's colour contrast was not visible to passive calorimetric infrared detection. In order to be identified by means of this type of sensor, which is used for diurnal and nocturnal aerial observation, the temperature of the emblem needs to be from 10 to 100ãC higher than that of its background.

    4052 The materials which may be used to make the emblem visible to the above means of infrared detection are therefore those which improve the dark-on-pale contrast or, in other words, enhance the reflective roperties of the white ground and diminish the reflected radiation from the red sign. Industry produces reflectorized materials which have been described in the International Review of the Red Cross and have proved most effective in improving the distinctive emblem's contrast under infrared observation. (6)

    ' Ph. E. '

    NOTES (1) [(1) p.1174] Cf. ' Commentary II, ' pp. 241-243 (Art. 43, para 1);

    (2) [(2) p.1174] Ph. Eberlin, "Technical Note on the Colours of the Red Cross and Red Crescent Emblem", ' IRRC, ' March-April 1983, p. 77;

    (3) [(3) p.1175] Ph. Eberlin, ' Protective Signs, ' op. cit. The crescent is obtained by making the circumferences of two eccentric circles intersect; their centres are two units of measurement apart and their radius measures 6 and 5 units respectively. The crescent may be pointed in various directions in relation to the centre of the circles;

    (4) [(4) p.1175] Cf. supra, general introduction to the commentary on Annex 1, p. 1144;

    (5) [(5) p.1176] "mu" = Greek letter (mu); under the International System of Units (SI), "mu" = micron or micrometre, also abbreviated "mu". One micron = 10(-6)m = 0.000001 m. Infrared wavelengths may sometimes be expressed in millimicrons (mmicron), nanometres (nm), or angstroms (ä); 1 micron = 10(3) m micron = 10(3)nm = 10(4) angstroms;

    (6) [(6) p.1177] Ph. Eberlin, "Modernization of Protective Markings and Signalling", ' IRRC, ' March-April 1979, p. 59;