[Darksky] Re: [Ida] skyglow, luminaire design and future trends (fwd)

[Jan Hollan]

... posting here too, to make the letter visible for robots...

---------- Forwarded message ----------
Date: Sun, 29 Oct 2006 15:42:42 +0100 (CET)
From: Jan Hollan <jhollan , amper.ped.muni.cz>
Reply-To: "conference of (European) IDA section leaders"
    <ida , amper.ped.muni.cz>
To: ida , amper.ped.muni.cz
Cc: magnitude6 , yahoogroups.com
Subject: Re: [Ida] skyglow, luminaire design and future trends

Dear friends,

I'm sorry I cannot follow the recent discussions on our lists (I wish I
would have time for that...) but let me comment on two issues for which I
found interesting information recently and on one issue which is my
important theme since two years.

Even before comenting on excellent points by Andrej, let me remember the
perhaps most important issue: we (ignoring Tuscon-based leadership,
sorry...) should agree on a simple set of rules, as urged by Diego
initially in September.  There is such a proven set, contained in six
regional legislations in Italy. My simplified formulation in English,
adding billboard luminance limits, is at
    http://amper.ped.muni.cz/light/law/Jan06/
 -- if you have any comments on it, please write to me directly, I might
not notice your comments if posted to lists only. (Up to now I know of no
objections... maybe due to hardly anybody studying the text.) This or
slightly adapted text should be our tools. This is what we ask for. Added
light is a poison (at night, for people and all life) and should be
handled accordingly.

> 1.)     Low pressure sodium (LPS) lamps are going out of use. CIE push color
> rendering. LPS is monochromatic and this is the reason why LPS is not (or
> almost not) in future plans.
>
> In Slovenia LPS has market share 0.1% or less. Luminaire design by using LPS
> is very complicated and expensive due to large light source.

I recommend everybody studying carefully the text by two most renowned
experts from Lighting Research Center, School of Architecture, Rensselaer
Polytechnic Institute,

     * Rea, M. S. and J. D. Bullough. 2004. In defense of LPS. Lighting
       Design and Application 34(9): 51-55.
       URL: http://www.iesna.org/PDF/Archives/2004_09.pdf

 (No wonder Chris Luginbuhl mentions it, even if without URL, on his main
 LPS page, as accessible from
        Christian B. Luginbuhl's Homepage
        URL: http://www.nofs.navy.mil/about_NOFS/staff/cbl/ )

Perhaps, translating it into another languages might be useful.

There are sure cases, as luminaires over centres of streets in Vienna
(they use no poles if possible, just wires attached on buildings), where
limited possibilities of optical control are no problem at all. They use
pairs of (36W probably) linear fluorescent tubes traditionally, with
3-wire supply to switch easily each second tube off after midnight. What
remains shining after midnight, should be LPS tube however (18W probably,
35W may be too strong...) in future, not a fluorescent one.

> Cosmopolis is more energy efficient compared to HPS and almost like LPS.

But just the Gold variant enables dimming deep enough..., acc. to Philips.

> If lighting engineers use modern sources with more blue part, a luxmeter
> would  show let's say 30 lux,
> but perception of human eye would be like to have for example 100 lux. This
> is because in low light level human eye is much more sensitive to blue part.

The difference is not that large. There are three dissertations on proper
formulas for mesopic luminances, all from Finland (2005 and 2006).

        TKK  electronic dissertations by year
        URL: http://lib.tkk.fi/Diss/list.html

     * Ketomäki, Jaakko: Effects of Lighting Parameters on Contrast
       Threshold in the Mesopic and Photopic Luminance Ranges. Electrical
       and Communications Engineering. October 2006.
       URL: http://lib.tkk.fi/Diss/2006/isbn9512283344/
and
     * Eloholma, Marjukka: Development of Visual Performance Based
       Mesopic Photometry. Electrical and Communications Engineering.
       October 2005.
       URL: http://lib.tkk.fi/Diss/2005/isbn9512278685/

     * Orreveteläinen, Pasi: Models for Spectral Luminous Efficiency in
       Peripheral Vision at Mesopic and Low Photopic Luminance Levels.
       Electrical and Communications Engineering. October 2005.
       URL: http://lib.tkk.fi/Diss/2005/isbn951227857X/

HPS and even LPS are still the winners. Blue should be suppressed above
0.3 cd/m2, if not filtered out completely. It does too much harm. I agree
with using white light below 0.2 cd/m2, assuming wildlife conservation is
not an issue at the site.

> 2.)     We must request from CIE to lower road illuminance standards if FCO
> are used
>
> FCO (full cut off) lights have less glare. In case of less glare the road
> illumination can be lower to have the same effect of visibility.
>
> IDAs need clear statement:  in case of using FCO luminaires roads can be lit
> with 40 lx instead of 50 lx or 0.8 cd/m2 instead of 1 cd/m2
>
> or something like this for all types of roads.

Let's demand more: make no recommendation for average luminances (or
illuminances), just for the minimum ones. And limit maxima to twice the
minima. The larger the maxima, and the larger the average, with minimum
values unchanged, the worse the visibility. Average is a wrong parameter.
Or do you think otherwise?

jenik


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