The following two images tell the tale; both are un-retouched computer output.
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| Rendering of space on the day of our main site visit, 15 May, 3:30pm. Although this looks dark, it is adequate light; the image is darkened to show the broad range of contrasts. |
Rendering of space on 21 December (winter solstice) 5pm. The sun has set. The yellow tone would not be visible if one were in the space; it is the absolute tone of the lamps, referenced against 5000º K daylight.
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The following diagrams show the illuminance on a plane slightly about table height (3.5' above the ground to show both the top of the librarians desk and the tables.)
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Illuminance in daylight in May. It is in the 300-500 lux range, an appropriate level for reading by British and American IES standards ([MEEB] section 18.24, pp. 937, 938, passim.)
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Illuminance after sunset on solstice. All illuminance is below 187.5 lux, which is not considered adequate for reading by British and American IES.
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