11/23/2023 0 Comments Cd to lumens![]() Prolonged exposure to light damages materials such as paints and dyes, especially the natural ones. In museums and conservation programs measuring luminous intensity helps determine the best balance between providing enough light to view the piece of artwork or an artifact, and making it subdued enough to reduce damage to the piece caused by light. For example, it is only 125 cd at a 30° angle, and only 50 cd at an 80° angle. Here it is 225 cd at its peak at 0°, and then it decreases fast with the decrease in angle. The red light, on the other hand, is more directed. The yellow light is similar to candlelight, relatively uniform in all directions. In the diagram the two light sources, red and yellow cover an equal area of space. For a diffused light, for example, a candle, moving away from 0° will reduce the luminous intensity at a lower rate, if at all. If the light source is directed, for example, an LED flashlight, and the direction straight ahead along the beam is taken for 0°, then moving away towards 180° will greatly reduce the luminous intensity. ![]() The value of this function is the highest for the light of a wavelength of about 550 nanometers, which is a green light, and lower for longer or shorter wavelengths.Ĭhanges of an angle in the plane where the light is distributed also change the luminous intensity, as shown in the diagram. It is easy to see from the formula for luminous intensity: it depends on the luminosity function, which in turn is different for different wavelengths. This is because the luminous intensity is adjusted based on the way different wavelength light is perceived by people. Luminous intensity is considered to be a unit of power, but it is different from conventional power because it varies not only depending on the energy of the source, but also on the wavelength. In this case, the latter will appear brighter, even though their luminous intensity is the same. Two objects with the same luminous intensity can also appear to have different brightness if, for example, one is diffused light and one is a point light. Different people can think of the same light to have varying brightness, even though its luminous intensity did not change. Brightness is also generally not perceived at a specific angle but evaluated more holistically. It is different from brightness, which is a subjective value, as perceived by the human eye. Luminous intensity is a physical characteristic of light. It considers only the focused light and not the light dispersed in all directions. ![]() Luminous intensity measures the power of a light source for a given unit solid angle. Measuring Luminous Intensity and Distribution Luminous Intensity in Museum Conservation Projects
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