Re: Lighting & Vision
- From: phil-news-nospam@xxxxxxxx
- Date: 18 Feb 2006 23:02:38 GMT
On Fri, 17 Feb 2006 22:34:22 -0500 Victor Roberts <xxx@xxxxxxxxxxxxxxxxxxxxx> wrote:
|> On the other hand there is a
|>simple and well-established method for such a lighting application and
|>that is to employ the highest CCT (correlated color temperature)
|>acceptable to the users. This result has been documented by repeated
|>studies by Berman et al and independently by Navvab published in the
|>peer reviewed Journal of the IES. McGowan implies that these studies
|>are controversial, but the results have never been found by anybody to
|>be incorrect. The controversy as raised by IES and CIE appears to be
|>whether they apply for general lighting practice beyond an application
|>that calls out for best acuity. The IES & CIE concern seem to based on
|>the their belief that in the workplace environment one never encounters
|>letters or objects small enough to be at a typical visual acuity
|>limit.
|
| Sam - you know that my expertise is in the area of light
| source technology, not vision science, but I find the
| position of the IES and CIE to be quite amazing. I have
| found myself working near what I believe is my visual acuity
| limit even when I was much younger than I am now, and even
| in so-called "work environments." While my office always
| had adequate illumination, many conference rooms and
| especially meeting rooms at hotels conference centers are
| not well lit and I often had trouble reading certain
| documents.
I wish Sam had done a better job of spacing the paragraphs of his post.
That is another aspect of reading comfortably that he seemed to ignore.
I was not able to determine what his article actually meant, other than
that sufficient quality illumination is needed. But the issue that is
probably critical is just what is quality illumination. Certainly a
sufficint quantity of light is necessary. But what about the quality?
My own vision suffers from chromatic issues. I can also see the flicker
in many non-incandecent light sources, but I believe that is not the big
problem I have with certain kinds of lights. What I believe is my own
issue (and I speculate so for many other people) is the continuity of
the spectrum. It makes the difference between seeing the edges as a
fuzzy blur (for incandescent or other near smooth continuous spectra)
vs. seeing the edges as a set of distinct separate edges at different
sizes. It doesn't matter if the balance of the colors mixes to white.
What matters is how smooth the spectra is. I believe what is taking
place is that with a blur edge, the eyes will settle into a focus at
about the middle range. Then the amount of blur will dictate where the
effective acuity ends. But when there are multiple sharp edges, the
eye jumps around between them, especially between red and green, and
perhaps never settles down.
I get headaches trying to read with any fluorescent lighting. This
happens within 20 minutes, typically. Other tasks can stretch that to
45 minutes or so. But that isn't enough for tasks like preparing a
large dinner, so I can't even use fluorescent lights in the kitchen.
I have tried reading under monochromatic light sources. Red works best.
Green works fine but doesn't give me quite the detail as red does. Blue
doesn't work very well. Mixing red and green together gave me the same
problems I got with fluorescent lights.
Reading text on a CRT screen has a similar issue. Red alone works best
(and black text on red background seems a tad bit better, probably because
the iris opening is smaller). Green works fine, and blue is bad. Yellow
is a mix of red and green is is lousy (as bad as, or worse, than blue is
alone). Uniformly adding one or two colors for both background and text,
leaving the contrast edges in a single color only works just as well. So
orange letters on a dark green background works well, as do a kind of pink
I get on dark cyan by adding in some blue as well. The contrast edge is
still strictly in the red color, and it focuses quite well.
So I will stick entirely with incandescent lighting for now, preferring
low voltage halogen to, hopefully, get the whitest light efficiently.
I have hope that LED lighting could achieve a good light, not with just
3 colors, but with perhaps as many as 24 distinct colors spread across
the spectrum. LED chips that can emit such a variety of colors already
exist commercially. Getting them all at sufficient light levels, and the
necessary balancing of intensity, would still be an issue. I wonder if
fluorescent material could be formulated to do something like that.
--
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| Phil Howard KA9WGN | http://linuxhomepage.com/ http://ham.org/ |
| (first name) at ipal.net | http://phil.ipal.org/ http://ka9wgn.ham.org/ |
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