[Neuroscience] Re: Light and dark adaptation of the eye

r norman via neur-sci%40net.bio.net (by r_s_norman from _comcast.net)
Sat Oct 14 11:54:24 EST 2006

On 14 Oct 2006 09:45:23 -0700, "Tim Allen" <tim.allen from gmx.com> wrote:

>I´d like to know if someone can help me with the following: Is it true
>that the rods (during dark adaptation) and the cones (during light
>adaptation) on the retina do all adapt to the same ambient light level
>or do they just adapt to whatever light intensity hits them? If the
>latter should be right this mechanism could be a powerful tool to
>strech the eyes ability to deal with the enormous variations in light
>intensity that we are exposed to. As I´m not totally shure that this
>is the right group for this question I do cross-post it to

I am not sure just what you mean.  The receptors can only adapt to the
light intensity to which they, themselves, are exposed.  There is no
'eye averaging' system that measures an 'overall' illumination and
gets all the receptors to adapt to that level.  However it is true
that generally all the receptors in the eye are subject to an overall
exposure to  the same background light intensity with the image
producing only a relatively minor change in intensity for specific

>However, thanks a lot for your answers!
>Tim Allen

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