Hello Elise,

There is a lecture by Psychologist Jeremy Wolfe from MIT about Sensing
with a focus on visual issues including the collection of light.  If
you have iTunes search for Jeremy Wolfe and then find Lecture 4.  The
podcast is free and the lecture entertaining and informative.

Jeremy has a booked called Sensation and Perception (edited by Jeremy
and a few other colleagues). It has a section on Dark and Light
Adaptation which discusses some of the factors that affective
perceived brightness and intensity.  The range of sensitivity is
really pretty incredible from a small number of photos that can be
perceived under complete dark adaptation to the light that ones sees
when looking at white sand at mid-day in the desert.  Wolfe discusses
how the interconnections in the cells of the retina influence
perceptions of brightness.  My memory is a little weak on that.

The sensitivity of the eye is affected by dark adaptation.  If I
remember correctly from my courses in physiological psychology,
sensitive to light increases to a maximum after about 30 minutes in
the dark.   The sensitivity is related to the regeneration of the
pigments in the cones and rods.

There is some research showing that light sensitivity during dark
adaptation increases more slowly with older adults which might
contribute to night vision problems in older adults.

The brightness of mono-chromatic light varies with wavelength because
the photopigments in the eye have different sensitivities.  This
causes an effect called the Purkinje effect where different colors at
equal light levels will appear to be different in brightness.  See the
Wikipedia entry which explains it pretty well:
http://en.wikipedia.org/wiki/Purkinje_effect

The perception of brightness is influenced by the context -- there are
some illusions that illustrate this point where the intensity of a
background influences the perception of the intensity of a stimulus
embedded in the background.

The best sources of information on perception of brightness and the
internal and external forces that affect brightness (and a related
measure called "lightness") would be general human factors texts.
There will be sections on visual mechanisms that control brightness
and external factors that influence the perception of brightness.  You
will find that measures of brightness are related to intensity by a
power function.
The basic HF texts should be a start for you.

I really enjoyed courses on sensation and perception like this which
explained why lime green might be a better choice than bright red for
fire engines and why certain plants appear brighter or more intense in
the twilight hours of the evening (the Purkinje effect).

This is a good topic.

Chauncey


On Wed, Jun 4, 2008 at 3:09 PM, Elise Edson <[EMAIL PROTECTED]> wrote:
> Hello IxDAers!
>
> My team has received a request from the mechincal engineering team to help
> them understand how the human eye perceives relative brightness of light.
> Specifically, how sensitive is the human eye to changes in brightness?
>
> An initial literature search on ACM & Google did not yield results.  Can
> anyone recommend any articles or other resources, or does anyone know about
> related research on this topic?
>
> Kind regards,
> Elise
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