Maker Pro
Maker Pro

New Photosensor Provides Support for Scotopic Vision Research

V

Victor Roberts

Jan 1, 1970
0
As many of you know, Sam Berman has conducted research for
many years that shows that a light source with a
scotopically-enhanced spectrum will result in reduced pupil
diameter and enhanced vision compared to a light source with
a non-enhanced spectrum that produces the same light levels
when measured with a standard photopically-corrected light
meter. These results were originally attributed to
activation of the rods, which are known to be responsible
for scotopic vision. However, there has always been
controversy about this explanation for the effect measured
by Berman, et.al.

Recently a new photoreceptor that has a peak sensitivity at
about the same wavelength as the rods has been discovered.
Sam believes this new photoreceptor provides a better
explanation for the reduction in pupil diameter with
scotopically-enhanced light.

Sam has written an interesting paper that describes the new
research. Attached below is an abstract provided by Sam and
the link to his paper, which I have posted on my web site.





ABSTRACT

NEW DISCOVERIES IN VISION AFFECT LIGHTING PRACTICE
Sam M. Berman (sam dot berman at comcast dot net)
Senior Scientist Emeritus
Lawrence Berkeley National Laboratory
Berkeley, CA 94720



For more than the last 100 years many lighting users and
practitioners have found that their sense of brightness of
spaces often does not tally with light meter values. Areas
lit by lighting with white light with more of a bluish tint
often appear brighter than the same areas lit by lighting
with more of an orange or reddish tint even though a light
meter may indicate the opposite, (e.g. compare 5000K
fluorescent with HPS). Lighting professionals have puzzled
over this observation for just as long but have failed to
provide a satisfactory explanation. Furthermore for about
the same 100 years most of us including lighting
practitioners have operated under the impression that there
are two photoreceptors in the retina of the eye, namely
cones and rods. However, very recent discoveries in vision
science have determined that there is another photoreceptor
in the eye relatively more sensitive to blue color and whose
responses are not included in the standard calibration of
light meters. This discovery can provide the mechanism for
an objective explanation of the paradoxical brightness
perceptions. Incorporation of this new discovery into
lighting practice will lead to lighting that provides better
vision and energy savings. An overview and some insights are
provided in my article appearing on the website -
http://www.robertsresearchinc.com/P...veries_in_Vision_Affect_Lighting_Practice.pdf

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
 
P

Paul Ciszek

Jan 1, 1970
0
Interesting stuff, Victor, thanks.

On this topic, sort of: Is there a consensus as to which wavelength
of light would provide the most energy-efficient illumination if you
had to pick just one? i.e., suppose I want to run emergency lights off
of batteries, don't care about aesthetics, and I think that LED's might
provide the best time/brightness tradeoff if I get some that only make
the "best" wavelength.
 
V

Victor Roberts

Jan 1, 1970
0
On this topic, sort of: Is there a consensus as to which wavelength
of light would provide the most energy-efficient illumination if you
had to pick just one? i.e., suppose I want to run emergency lights off
of batteries, don't care about aesthetics, and I think that LED's might
provide the best time/brightness tradeoff if I get some that only make
the "best" wavelength.

For the light adapted eye, which is defined by the IESNA as
subject to illuminances greater than approximately 3 cd/m^2,
the peak sensitivity occurs at about 555nm. For the dark
adapted eye, defined by the IESNA as subject to illuminances
less than about 0.001 cd/m^2, the peak eye sensitivity
occurs at about 507 nm. Since your light level will be
most likely be between these two values, the peak eye
sensitivity will occur at some intermediate wavelength.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
 
V

Victor Roberts

Jan 1, 1970
0
Yes and No,

Depending on the mathmatics used to "normalize" the curves.... LPS
single frequency can be shown to be 6 times less visually efficient
than a continous curve. That could take your 200l/w to near halogen
efficiency.

(Sorry can't find the referance article. I do recall the James Benya
was involved. Anyone else have that link?)

While not accepted widely the idea does get some help from Sams
arguments.

RickR


If you use the photopic eye response curve that is currently
the accepted standard, then LPS is the most efficient
source. If, on the other hand, you believe that Berman is
correct and you reject the current standard, then LPS is not
the most efficient source.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
 
D

Don Klipstein

Jan 1, 1970
0
For the light adapted eye, which is defined by the IESNA as
subject to illuminances greater than approximately 3 cd/m^2,
the peak sensitivity occurs at about 555nm. For the dark
adapted eye, defined by the IESNA as subject to illuminances
less than about 0.001 cd/m^2, the peak eye sensitivity
occurs at about 507 nm. Since your light level will be
most likely be between these two values, the peak eye
sensitivity will occur at some intermediate wavelength.

3 cd/m^2 sounds to me the brightness of an ideal diffuse "lambertian"
100%-reflective surface being illuminated by 3*pi lux or 9.42 lux or
..875 footcandle.

I did just go out and see how bright surfaces illuminated by 12 lux of
HPS light and 12 lux of apparently-nominally-metal halide light appeared
to me. To central vision, they appeared to me similarly bright.

On the other hand, HPS gives me "less of a sensation of illumination"
then such metal halide does even at illumination level into the 100-150
lux range. I suspect this is from scotopic vision contribution to
"my personal illumination sensation" through peripheral vision.

Meanwhile, my experience with "office and brighter retail illumination"
at a kilolux or somewhat more is that my "sensation of illumination"
tracks well with photometric readings and theoretical calculations based
on photopic vision regardless of the light source type as long as it's
reasonably white, 3000-7000 K with CRI at least nominally 54.

I can also say that 6500 Kelvin lamps in home use usually appear
to me "dreary gray", and that doubling the illumination photometrically
does not double "my sensation of illumination". I suspect that pupil
constriction by strong scotopic vision stimulation makes things look
dimmer than if the color temperature was lower.
For that matter, I tried carrying around a light meter on a day with
overcast skies and varying brightness, with color temperature appearing to
me to be about 6000 K. At that color temperature, it took about 5
kilolux for things to look good to me! Preferably more!

Back to home illumination - 3500K appears to me to only need 150-200 lux
to look good. Around or above this, this is my favorite CCT for most home
illumination. And 2700-2870 K or so appears to me good at most
illumination levels below 100 lux.

Now for dim home light to nightlight range: At a few lux, I suspect
favorite will be low 2,000's Kelvin with decent CRI and scotopic/photopic
ratio close to usual for such CCT, along with red content not much less
than in blackbody light of such CCT.

At a lux or two, I surely like upper 2,000's K, with high CRI and no
less red spectral content than with same CCT blackbody as well as
scotopic/photopic ratio close to blackbody.

But under a lux, gimme scotopic vision stimulation, unless it's going to
be a nightlight that is a "warm glow to look at" (neon glow lamp or vacuum
tube radio) more than something to see by.

- Don Klipstein ([email protected])
 
D

Don Klipstein

Jan 1, 1970
0
If you really don't care about aesthetics and can live with nearly
monochromatic bright yellow then low pressure sodium SOX lamps have
just about the highest ~200 lumens per watt available at 590nm. ISTR
the smallest wattage bulbs are around 18W and they require a suitable
ballast and ignition circuit.

Despite being a bit off the mark for wavelength I reckon it still wins
hands down for energy efficeincy.

The 18 watt version has about half the efficiency and luminous efficacy
of the 180 watt version. And I thought the 180 watt version got closer to
180-185 lpw than to 200.

The CRI is -44 by one common measure.

Rendering red, green, blue and most purple objects as close to black
detracts from percentage of illumination being reflected by colored
objects.

Very low ratio of scotopic/photopic ratio can amke this appear dimmer in
many situations when illumination level is around/under 100 lux
(possible even somewhat more) even where color does not matter.

Besides, color distortion is very severe - generally close enough to
"an orange-yellow version of black-and-white" with exception of a few
reddish objects managing to fluoresce from the 589 nm wavelength.

I suspect LPS has had limited popularity for the above reasons, and many
people would prefer metal halide, better fluorescent lamps, etc.

- Don Klipstein ([email protected])
 
Top