Am 29.01.2017 um 15:13 schrieb Alain:

>> I'll have to render some _dark_ scenes and then check them out after
>> adapting to
>> the dark...
>>
>>
http://www.laserfocusworld.com/articles/print/volume-52/issue-01/features/photonic-frontiers-color-measurement-light-so
>>
>> urces-and-vision-led-lighting-makes-new-demands-on-color-measurement.html
>>
>>
>> "In mesopic vision, eye response varies from the photopic extreme of
>> fully
>> light-adapted (m=1) to the scotopic extreme when fully dark-adapted
>> (m=0). Note
>> that the eye is far more sensitive to blue light in the dark, making
>> blue light
>> look brighter at low light levels. (Courtesy of Teresa Goodman, National
>> Physical Laboratory, UK)"
>>
>>
> 
> This look strange. Blue light cause your iris to contract, reducing the
> amount of light that enter the eye. It also cause saturation of the sick
> cells in your retina, killing night vision. At the same time, the eye is
> far more censible to light in the yellow region whitch don't cause
> saturation nor contraction of the iris.
> When sodium lighting was adopted, the considerations where:
> It pierce fog and smoke.
> It preserve night vision.
> It takes less lumens to get the same physiological brightness.
> The lumen to wat ratio is higher.

... and they _may_ have been wrong in their assessments back then.
Science advances as people make more and more experiments and field
studies, and do so in an increasingly controlled manner.

Also note that the article does not conclude with "We should make LED
street lamps less bright", but "We have more to learn about the impact
of LED lighting on color measurement, standards, and illumination."


Besides, are you sure the 3rd and 4th criteria on your list actually
reflect the considerations back then? I'd have expected them to be
collapsed into just a single criterion:

    "It takes less Watts to get the same physiological brightness."

That is, unless legislation about the brightness of street lights had
already been in place then -- because there is no other reason to worry
about the lumens -- in which case my guess would be that the 3rd
criterion wasn't considered at all, just the 4th criterion.


And last not least, road illumination should (well, _must_) consider
interaction with other important sources of illumination present on dusk
and night roads, most notably car headlights. Back when sodium lamps
were introduced, tungsten incandescent bulbs were the prevalent means
for cars to carry their own light source, but there is a long-standing
trend towadards xenon lamps (and also those idiotic "fake xenon"
blue-filter tungsten lamps), which have a significantly higher
temperature, and I guess there's also the occasional LED headlight out
there by now (not to be confused with the already common white LED
"position lights" intended for daylight use).


(Besides the issue of visibility, "blue" street lights would also have a
slight advantage in keeping drivers awake at night. And a corresponding
disadvantage in also more strongly influencing the day-night rhythm of
local residents, both human and animal.)

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