camera measurement of blue light

[Jan Hollan <jhollan@amper....muni.cz>]

Dear promoters of filtering the left half of light spectrum,

thanks for the great new site. This is a field I had a poster on in Graz
last year, see it ev. within
     g_camer.pdf
 at
     http://amper.ped.muni.cz/noc/english/canc_rhythm/

There is also a formula for the melatonin-affecting spectral sensitivity,
I think the best one at that time (October 2004).

I'd also like to point your attention at yellow fluorescent layers within
linear tubes, which are produced by several manufacturers. These are, in a
sense of efficiency, better than filtering by additional outside layer. I
use them at home. They are roughly twice the price of standard
broad-spectrum ones.

On the other side, I'd be cautious in proposing any need to filter out the
blue-green component of light, if it gives always < 0.3 lx illuminance of
the eyes, as even white light can hardly have any influence on lowering
melatonin production at this intensity, assuming people having > 100 lx
daylight in the daytime phase. In fact, white light is better filtered by
eyelids than red light... And light at < 0.1 lx illumination of the room
serves surely better its purpose (good orientation) when rich in scotopic
wavelengths too.

On the other side, I personally use glow-discharge bulbs for long years as
the only nighttime illumination, when such is needed (needed: esp. such
cases where people otherwise switch on light if they go through a dark
room or corridor to a toilet late at night). And these are mostly red...
well, magenta in fact, having some faint blue component too, working well
for scotopic vision too. Great light sources, neglected due to erroneous
striving for far more light everywhere.

with best regards,

jenik

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                                Jan Hollan
              N. Copernicus Observatory and Planetarium in Brno
Kraví hora 2, CZ - 616 00 Brno                        +420 5 41 32 12 87

                                   home:
Lipová 19, 602 00 Brno                                     5 43 23 90 96

               volunteer of the Ecological Institute Veronica
Panská 9, 602 00 Brno, Czechia                  fax:  +420 5 42 21 05 61

e-mail: hollan@ped....cz             http://astro.sci.muni.cz/pub/hollan
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