World of Decline

Naturalistic Synthetic Light Environment

Posted in Uncategorized by isochroma on February 24, 2011

There’s something magic about outdoor light on a clear sunny day. Such a day combines wide-and-high viewfield bright blue =>15K CT with the narrow-beam lower CT sunlight.

For the synthetic setup, the idea is to use blue lights that throw light horizontally in a continuous distribution combined with one or more ‘white’ 7000-8000K lamp(s).

The effect of pushing the ambient light – reflecting to the eyes from the walls and ceiling – to a highly blue-dominant or even exclusively blue spectral power distribution is to simulate the great expanse of blue sky.

The intent of these simulations is to create both an instinctually-believable [credible] daylight-with-sun environment with maximum circadian power, and to create the higher-level psychological impressions of both ‘broad sunny daylight’ and the more difficult, positive items that so vary between individuals.

Back to the technics: the blue ambient surround, particularly that in the upper portion of the visual field – spacial circadian receptor distribution is nonuniform – functions to convince the circadian system that it is indeed ‘full day’.

The ‘white’ 7000-8000K lamp or lamps are not uniform emitters like the ambient blue lamps. Instead, the white lamps are to be focussed on task areas (tables, desks) or places the person will be. Optimally, units should be placed on the ceiling with a fixed or preferably a single or dual universal joint.

The white lamp itself is to be LED, and for several good reasons. First, the LED lamp’s specialty is direction, and the application requires it. Second, the LED lamp provides the perfect color temperature – 7000-8000K – for both the required circadian and the needed psychological effects.

To really explain how it all comes together, the blue surround tells the circadian system ‘it’s day!’, and the white spot(s) tell the person, ‘sunlight’. You might wonder why a person would easily confuse 7-8K with sunlight, and I’ll give the answer.

The magic is called chromatic adaptation. We all know much about how the eye adapts to differing light intensities – pupillary constriction or dilation and receptor bleaching/resensitization.

Chromatic adaptation allows the eye to ‘adjust to’ large changes in color range (here, CT or CCT) in a matter of minutes. For example, walking in from a bright blue-white daytime excursion to a supermarket lit with 4100K fluorescent, the environment appears yellowish. However, in a matter of a minute or two, checking again the new customer sees white. His eyes have adapted by a shift in chromatic sensitivity, or his brain (visual cortex) has adapted, or both.

The smaller ‘white’ area(s) provide the user(s) with a warmer sense of localized sunshine. The key point is that normally, this ‘white’ light would be seen as bluish-white – however, in an environment saturated by decently bright blue or high CCT flux, the eye adapts to the larger brighter scene in view as the ‘base’ from which to ‘measure’ the color of everything else, including smaller light sources.

Thus under the new sky blue, the 7-8KK light looks pure white in comparison. Of course it mixes with the ambient-blue light. The white light is a weaker circadian stimulant than blue, but provides important psychological effects.

These effects are to ‘fill’ local visual field from the midline to the lowest areas with a CCT of light that can complement the cold, expanded, dimmer blue surround with its own warm, condensed, brighter nature. To achieve these ends both narrow-beam LED lamps can be used, and wide ones too, provided they do not intrude too much on the ‘sky’ area. In the spacial-spectral transition region the two should intermix naturally as visible from typical white walls.

Finally, the lamps in question:

White LED Lamp: New E27 6W 3x2w LED Spot Light Bulb Lamp White 85V-265V $6.64 USD

Blue LED Lamps: Either a cluster of 13W blue-coated CFLs from the hardware store or a high-CCT metal halide bulb. Cluster currently in use: 15x13W blue-coated CFLs 195W total and emitting at ~12-17KK.

Blue and high CCT (15KK+) metal halide bulbs are for sale. They are available in CCTs of: 10KK, 13KK, 15KK, and 20KK. When burned vertically, the arc is short and emits a nearly uniform photic distribution around its circumference.

For situations where a protective fixture is available or the risk is minimal due to building features (high ceiling, high airflow, concrete or other synthetic floor, fewer combustibles per square meter of combined floorspace and relevant objectspace, the bulbs can be run unshielded but this is not recommended.

Not having the required fixture, the first implementation of the Naturalistic Synthetic Light Environment is to be run with an ambient-blue lamp system based on the CFL data above.

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