4 Answers
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Measuring Lumens - What Are "Pupil Lumens"?
How people see and are psychologically impacted by lighting has been a subject of much study and discussion for years. Describing light as "lumen output" and measuring it as "foot candles" on a work plane have been the traditional ways of describing and defining how much light is required to perform a variety of tasks. However, that is being re-examined based on results of studies on visual performance and the psychological impacts of lighting. Additionally, the "colour rendering index" (CRI) and correlated colour temperature (CCT) describe the quality of the light (relating to how true colours appear compared to under a noon north sky on a clear day).
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Pupil Lumens
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How people see and are psychologically impacted by lighting has been a subject of much study and discussion for years. Describing light as "lumen output" and measuring it as "foot candles" on a work plane have been the traditional ways of describing and defining how much light is required to perform a variety of tasks. However, that is being re-examined based on results of studies on visual performance and the psychological impacts of lighting. Additionally, the "color rendering index" (CRI) and correlated color temperature (CCT) describe the quality of the light (relating to how true colors appear compared to under a noon north sky on a clear day). As lighting technology evolves into various types and colors, simply measuring the lumens proves not to be fully adequate in predicting how well people can see. An excellent example is the low-sodium lamp which produces many lumens, but only two colors (yellow and gray); the ability to make out details—beyond shapes of objects—is lost under this light source. Different light sources produce light in different spectral ranges and there is a wide variety of spectral output available in fluorescent lamps.
Vision itself is affected by many factors, from light intensity, distribution, color, and contrast, as well as reflections, glare, air quality, motion of subjects and viewers, and more. Our eyes use different parts to see in bright light and low light conditions. The eye contains cones and rods which were thought to work in opposite conditions. Cones provide color vision and fine detail (photopic) in bright light and rods take over in dim light (scotopic). In bright light our pupils contract allowing more detail to be perceived, while depth of field and perceived brightness also increase. In low light our eyes dilate to allow more light in.
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It is all to do with the amount of light. If your in a dark room your pupils will get bigger to try and get more light in to help you see better and if your outside in the sun they will be smaller so you don't get blinded. Its just your eyes adjusting to your surroundings. Hope this helped 🙂