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Re: Eyes versus instruments
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Re: Eyes versus instruments


  • Subject: Re: Eyes versus instruments
  • From: Roger Breton <email@hidden>
  • Date: Fri, 06 May 2005 18:11:47 -0400

> Just to further confuse the issue, I believe there is data which
> suggests that at lower brightnesses (e.g., museum lighting levels)
> the rods come back into play and shift our color perceptions.

I'd like to see that data. According to Dr. Ethan Montag, psychophysicist at
the Munsell Color Science Laboratory, in photopic vision, our rods are
always over threshold, effectively "shutting them off".

I don't know at what exact illuminance level our cones become inactive but I
tend to think that this level is way below what in my experience I've seen
museum lighting to be.

> All the standard colorimetry pretty much assumes that only the cones
> are in play - which is indeed the case under the conditions in which
> they gathered the standard observer data, but may not be fully
> accurate in dimmer viewing rooms.

The only thing I can see which relates to your description is mesopic
vision, some vision taking place at twilight. But I'll admit I don't know
much about that type of vision.

> I believe some museums have discovered that D50 looks very "cold"
> rather than neutral under low lighting levels, and have shifted to
> "warmer" lights (3400K, etc.) to achieve the neutral appearance
> associated with D50 at higher illumination levels.

> Very very complicated our eyes...

But fascinating nevertheless.

> Garth Fletcher

Roger Breton  |  Laval, Canada  |  email@hidden
http://pages.infinit.net/graxx


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