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Whenever we design for lighting whenever we put lighting on
something, on any application at all, we really have to do it for one purpose and
one purpose only.
For people to see, and how do people see?
We see with our eyes. We see through vision.
And what we're going to do is we are going to discuss
how we see. here we see it cut section of the eye.
We have all sorts of different parts of the eye
with the cornea, the pupils, the lens, the iris. The information
our sight, comes in through the cornea,
and through the pupil, the lens, then focuses this information
back on the retina. The pupil
will dilate or contract just like a
camera lens depending on how much late is entering.
The retina is like a movie screen. On the back of the retina all the way
around the eye
there are three different types photoreceptors.
All around the peripheral an all-around
the eye, there is 120 million of what are called
rods. Rods are responsible for
peripheral vision. There's a 120 million number
of them all around the retina.Rods
have no color vision whatsoever we use our rods at very low light levels.
However rods are very very sensitive to movement.
That's why you may see something Flickr under the corner of your eye
because the corner of your eye, the peripheral vision is done
with your rods. In order to see
task in what's called a Fovea vision we need to use our cones.
Our cones are situated predominantly in the Fovea,
the Fovea is this area right here. There are 30
million cones and there are varying sensitivities. There are sensitivity in blue
red and green, the primary colors a light.
Cones are responsible for seeing in great detail
as well as color and they need little bit more light
than the rods in order to be able to function. The third photoreceptor
that doesn't have to do with vision was discovered in 2008.
Intrinsically photosensitive retinal ganglion cells
and what they do is they regulate our circadian rhythms, our natural
daily rhythms, ourre sleep-wake cycles. Two other terminology that we have to discuss
when we're discussing
lighting are adaptation and accommodation.
Adaptation is the eye's ability to go from light
too dark or dark to light. Light adaptation
going from dark to light happens very very quickly.
If you've ever left a dark area into a sunny outside
you'll see that it happens quickly. You may squint
because light adaptation happens very quickly
within about five seconds for 75 percent
adaptation. Going from light to dark however
can take an awfully long time. You can take
up to 15 minutes to get to eighty-five percent
total dark adaptation. That's why you when you go into a room
you have to adjust in order to be able to see. Accommodation is the ability to
focus.
Whether we focus close or far.
Sometimes our eyey, our lenses are unable to focus the
image that we see onto the retina perfectly.
So we may need some assistance such as these
and as we age these might be more and more
required. So it's absolutely critical to
have a basic understanding of how the I works and how we see
in order to progress through lighting in your profession.