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This is a continuation of yesterday's journal. I hope no one thinks I am plagiarizing again because this is my own work. Anyways, to continue on from yesterday... Discontinuities in light intensities, which are part of the luminance contour, are caused by two factors. These two factors are discontinuities in reflectance and discontinuities in illumination. Discontinuities in reflectance are called reflectance edges. A reflectance edge is a point of difference in the actual surface lightness of an object. This can be observed on a striped t-shirt with two different colors. The shape of a surface can also cause a reflectance edge. The edges that separate the surfaces of a cube would be a good example of this. Discontinuities caused by illumination are called illumination edges. An illumination edge is formed by causes that affect the illumination of an object. A few examples include reflective surfaces like shiny metal, dark environments, and a focused spotlight. In the actual environment there are two important facts about illumination edges and reflectance edges. Illumination edges appear fuzzy and reflectance edges appear sharp. These facts play a critical part in enabling the perceptual system’s capacity of luminance constancy.
The visual perceptual system is able to distinguish illumination edges from reflectance edges. This is because the visual perceptual system operates in accord with a certain formation principle. Over centuries, the perceptual system has had innumerable causal interactions with the distal environment. The system developed so it has law-like regularities, which reflect law-like regularities in the environment. It is an environmental fact that illumination edges are fuzzy and reflectance edges are sharp. Because of this environmental regularity, the perceptual system developed and operates on a certain principle. This principle is based on the sharpness or fuzziness of a luminance contour . Sharp luminance contours are highly likely to correlate with reflectance edges than with illumination edges. Fuzzy luminance contours are the exact opposite. Following this principle and environmental facts, the visual perceptual system can differentiate reflectance and illumination. Therefore, luminance constancy is possible.
The visual perceptual system is able to distinguish illumination edges from reflectance edges. This is because the visual perceptual system operates in accord with a certain formation principle. Over centuries, the perceptual system has had innumerable causal interactions with the distal environment. The system developed so it has law-like regularities, which reflect law-like regularities in the environment. It is an environmental fact that illumination edges are fuzzy and reflectance edges are sharp. Because of this environmental regularity, the perceptual system developed and operates on a certain principle. This principle is based on the sharpness or fuzziness of a luminance contour . Sharp luminance contours are highly likely to correlate with reflectance edges than with illumination edges. Fuzzy luminance contours are the exact opposite. Following this principle and environmental facts, the visual perceptual system can differentiate reflectance and illumination. Therefore, luminance constancy is possible.
