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Re: light intensities and latitude

  • To: Multiple recipients of list <iris-l@rt66.com>
  • Subject: Re: light intensities and latitude
  • From: "Jeff and Carolyn Walters" <cwalters@cache.net>
  • Date: Sun, 23 Feb 1997 09:22:17 -0700 (MST)

Hi Celia!
     You wrote (Fri, 21 Feb 97):
> I haven't yet seen latitude discussed here as a factor to consider when
> shopping for iris sources, and I wonder if it should be.
> NPR reported recently that a film student took a light meter reading out
> doors at noon on a clear, sunny day in New York, NY, and came up with a
> reading of 300-and- some-odd candle feet. The same week, a film student
> Los Angeles also took a light meter reading outside on a clear sunny day,
> and his clocked 700-and-something candle feet. (Sorry I don't recall the
> exact data, I was driving.) NYC is located at 40 degrees, 43 minutes N;
> sits at 34 degrees, 4 minutes N.
> This is a monster difference in light intensity, especially for living
> things whose food production depends upon how well they absorb and employ
> light energy.
> Although it's a perfectly logical observation, I had not considered how
> dramatically different light *intensity* (not merely duration) might be
> different regions.

In addition to latitude, I would think that atmospheric conditions (cloudy
or clear) and altitude would have to be considered in this connection.

Jeff Walters in northern Utah (Zone 4)
"This is the Place" -plenty of sun, but not enough heat at the moment

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