Mike, this might shed a little light on your question.
I cut this out of
http://www.parliament.vic.gov.au/rsc/1992cycle/mbch2.html
<snip begin>
2.1 NATURAL LIGHT CONDITIONS IN VICTORIA The ambient light intensity in any
part of the world depends on, first, the sun's angle above the horizon, that
is time of day, latitude and season of year, and, second, interference in
its light path by environmental particles such as smog, cloud or fog.
Daytime running lights were first introduced for all vehicles in Finland and
Sweden where the natural light intensity during the day is particularly low.
In Sweden the ambient light intensity on a clear day ranges from 2 000 to 26
000 lux and it does not rise above 10 000 lux when it is raining or foggy.
(Lux is a unit of light intensity measured at its point of impact rather
than its source.) In contrast, the average ambient light intensity in
Victoria at noon ranges from about 50 000 lux in June to 110 000 lux in
November.
The length of dawn and dusk are also much shorter in Melbourne than at
higher latitudes such as in Scandinavia.
The following discussion summarises generalisations about the way light,
colour and fluorescence affect conspicuity of motorcycles.
Brightness contrast is the most important influence on whether a vehicle is
detected by other road users. As well, the eye accommodates to see colour
better in daytime light than night-time light.
In bright daylight, the intensity of the sun's light is much greater than
the intensity of any artificial light source. Therefore, the visibility of
the light on a motorcycle becomes greater as the ambient light intensity
decreases and, at the same time, the brightness contrast increases. When it
becomes dark, the lamp's light becomes visibly radiant and its surroundings
disappear.
On the other hand, colour and fluorescence are visible because they work by
reflecting or remitting the light around them. Their effect on visibility
depends on their reflective characteristics and the background against which
they are viewed. Colour perception is almost absent at night. There is
general agreement that red, yellow and white colours and fluorescence are
most likely to increase motorcycle visibility under Australian light
conditions.
Therefore, the ability of any particular colour to attract attention
declines in intensity as the ambient light intensity declines, whereas the
effect of fluorescence depends on the light which it is remitting and on the
ambient light.
The potential safety effect of motorcycle conspicuity measures depends on
where they have to operate, the background against which other motorists
will see them and their particular specifications. As the natural light
intensity increases, the potential effects of colour and fluorescence
increase and the potential effect of daytime running lights declines. On the
other hand, as the natural light intensity declines at dusk, dawn and under
adverse weather conditions, there is an increase in the potential for lights
to attract attention while the influence of colour reduces.
<end snip>
----- Original Message -----
From: "Peter Creswick" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Tuesday, July 12, 2005 11:16 AM
Subject: Re: Fw: [Aus-soaring] FLARM
Another one worth a read.
http://www.optometrists.asn.au/gui/files/ceo874258.pdf
----- Original Message -----
From: "Peter Creswick" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Tuesday, July 12, 2005 11:08 AM
Subject: Re: Fw: [Aus-soaring] FLARM
The subject of " Conspicuity " is apparently the core issue. This is
only a couple of hundred kilobytes, but worth a read.
http://www.optometrists.asn.au/gui/files/ceo874294.pdf
----- Original Message -----
From: "Mike Borgelt" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia."
<[email protected]>
Sent: Tuesday, July 12, 2005 10:23 AM
Subject: Re: Fw: [Aus-soaring] FLARM
At 10:05 AM 12/07/05 +1000, you wrote:
Thanks for that Bernard, & the visibility, before fitting it
to
the ASW 28. That way I can return it in good condition and
without
drilling holes, if the light isn't outstanding in bright daylight.
Does anyone in this forum know what work has been done with battery
operated strobes in front of a focusing reflector to provide best
strobe
light in a defined direction? Best regards Geoff
Geoff,
I guess you could run some experiments with photo flash accessories to
try
the strobe/reflector thing.
Lights, particularly focussed forward strobes will help the head on
case(how narrow do you make the focus - the Ventus/Skylark 4 collision
was
at 30deg from head on) but of course don't solve the mutual blind spot
problem and for those who believe we don't have a problem a friend of
mine
who is an current Australian contest pilot has been to 3 contests where
pilots have died in mid airs and two more where mid airs occurred.
Mike
________
Also Adrian Jansen sent me this that he found the other day:
Mike,
Came across this for more than you ever wanted to know about photometry
of flashlights and visibility. Seems like its still an ongoing subject
for research.
http://cie2.nist.gov/meetings/1999_Warsaw/Workshop_Proceeding4.htm
Also some figures for light efficiency, all in lumens/watt:
Tungsten incandescent 12-20
Tungsten-halogen 18-25
Hi-efficiency fluorescent 45-60
White LED 25-60 ( best lab samples ~ 100 )
xenon HID arc ( continous ) 30-150
ideal white light 242 ( all energy converted to light )
ideal monochromatic 556 nm source 680 ( max eye sensitivity )
Xenon flash tubes are around 150, but because the flash is very short ~
1 msec, you can get very high peak intensities, not achievable by any
other source.
I havent found a number for the background intensity of the sky, or a
way of relating that to any of the above.
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
Int'l + 61 429 355784
email: [EMAIL PROTECTED]
website: www.borgeltinstruments.com
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