Mesurer le « développement durable » pour aider à le réaliser ?

Avec les enjeux du « développement durable », la production d’informations formalisées, organisées, chiffrées, a trouvé un nouveau domaine où elle est devenue stratégique. Les « indicateurs de développement durable » sont censés compléter les capacités de régulation publique pour sortir d’évolutions dommageables pour l’humanité et la planète. Cet article, à partir notamment des démarches des instances françaises et européennes, remet au jour les dimensions et dynamiques qui jouent dans le déploiement de ces indicateurs. Ils bénéficient en effet d’un réseau institutionnel et épistémique qui marque un degré d’organisation croissant dans une forme de surveillance à distance. Ils participent aussi à la structuration des cadres d’appréhension des problématiques et des enjeux en discussion. Forme de mesure mais aussi de perception, ces indicateurs se rapprochent d’une tentative de saisie du monde et constituent en quelque sorte des prises pour cette opération. Au-delà donc d’un simple aspect d’aide décisionnelle, ils peuvent alors être appropriés d’une manière qui en fait des technologies de gouvernement du changement.The issues of sustainable development have opened up a new area where the production of formalised, organised and quantified information is particularly strategic. The « Indicators of sustainable development » are intended to supplement the capabilities of public regulation, in order to withdraw from trajectories harmful to both humanity and the planet. Notably based on the initiatives of French and European authorities, this article sheds light on the dimensions and dynamics that come into play in the deployment of these indicators. Indeed, these make use of an institutional and epistemic network that reveals the increasing degree of organisation of a form of remote monitoring. They also play a part in the structuring of the frameworks used in apprehending concerns and issues for discussion. In that they are a form of measurement as well as perception, these indicators can be seen as tools to better grasp the world. Therefore, besides providing guidance for decision-making, they can become suitable as technologies of change management

The standard observer : a controversial subject

The efficiency of monochromatic light for the eye is expressed in the relative spectral sensitivity of the eye. In 1924, the ‘Commission Internationale de l’Eclairage’ (CIE) recommended a curve for this purpose that had to be representative for the average photopic observer. In 1931 this was incorporated in the CIE Standard Observer. The particularly important conception of luminance is defined with the aid of the relative spectral sensitivity. It is a measure for brightness and enables us to compare the light flow of sources of different color. It affords the possibility of specifying the adaptive condition under which visual tests have to be carried out. When more data became available, however, it appeared that the standard observer is less representative than initially thought. For example, its sensitivity in the blue is too low, and the spectral sensitivity of the eye proved to depend on many parameters, like field size and location on the retina. Moreover, the visual spectral sensitivities determined according to various methods prove to be mutually different. This results in the increasingly urgent question, i.e. under which circumstances a light measurement, normally based on the sensitivity of the standard observer, is adequate or not. In view of this, in the latest session of the CIE (1971) a new study of the methodologic foundations was recommended. At the same time, high priority was recommended for research into the spectral sensitivity of small fields and the specification of mesopic light. Both are of importance for perimetry and mesoptometry

Dynamic properties of vision-II:theoretical relationships between flicker and flash thresholds

\u3cp\u3eOn the basis of some general system properties theoretical relationships have been established between parameters which characterise the sensitivity and inertia of the visual system in flicker and flash experiments. The results are in good agreement with the experimental relationships found in Part I over a background intensity range of five decades. \u3c/p\u3

Brightness Contrast And Sharpness, Interactive Factors In Perceptual Image Quality

Brightness contrast is an important factor in perceptual image quality. In the case of a TV system it is dominantly determined by the luminance reproduction function. Subjective quality was found to be optimal for non-linear luminance transfer and closely related to (subjective) brightness contrast. Quality is also related to sharpness, which in turn depends on the non-linear transfer. Fortunately, in the neighbourhood of the optimum, quality is dominantly determined by brightness contrast. It will be shown that brightness contrast is not adequately characterized by the luminance contrast ratio, which is defined as the ratio of the luminance extremes. Alternative and more suitable contrast measures in terms of luminance are discussed

Dynamic properties of vision-I:experimental relationships between flicker and flash thresholds

\u3cp\u3eFlicker thresholds of harmonically modulated light with variable frequency and flash thresholds of square flashes of variable duration are compared quantitatively. The experiments were carried out with the same subjects under the same conditions and with the same equipment over an intensity range of five decades. Characteristic quantities for sensitivity and inertia are defined for both types of measurement. Sensitivity S for flicker and sensitivity F for flashes are found to have a constant ratio over the entire background intensity range. The product of the cut-off frequency with flicker and the critical duration with flashes is also found to be constant.\u3c/p\u3