Light and the Human Eye
HOW WE SEE:
The human eye looks basically like the crude drawing to the right. The lens at the left side of the eye focuses light rays onto the retina
at the right. The retina converts light rays into “electrical impulses” that are sent to the brain and our brain tells us we are seeing a bit of light.
A camera (digital or film) has a lens out front to
capture light rays, but those rays land on film or a digital chip…. both of which
are sensitive to light. Now we are jumping ahead of ourselves, let’s get back to
basics.
ABOUT LIGHT RAYS:
We have different labels for describing the rays we see. Here are a few basic ones:
Transmitted rays
When you look at a stop light the top light is red, the middle is yellow and the bottom light is green. That light is transmitted by putting a light source behind a colored filter.
Direct rays:
When you look directly into the sun, or a camera’s flash unit, or a flashlight … that is
direct light. The light you see is coming directly from the source.
Reflected rays:
When you look at anything, you can see that object because direct light is shining
on it and being reflected back into your eyes.
Ambient light:
Think of ambient light as stray light - light rays that are being bounced
around from all sorts of sources. If direct or reflected
light on the subject is stronger your subject will appear clearer and less hazy.
Available light
simply means whatever light is present … not using a flash or other sources of light.
NOW … ABOUT COLOR:
The COLOR of the subject is
determined by the color of the light source and the color of the subject.
Photographic film records light as it
actually is. Your eye/brain however, will always correct light back to
“normal”. Your brain compensates constantly.
That is…. if you are inside a place
that is lit with light bulbs, those light bulbs actually transmit a reddish-brown
light and white objects will be recorded on film as reddish-brown. However your
brain will correct that light and a white object will appear white.
Same thing inside a place illuminated
with flourescent bulbs. Flourescent bulbs actually transmit an ugly greenish-yellow
light, but your brain corrects that light and it appears white to your eye. Film
records that light as greenish-yellow.
Flourescent light contains green and yellow
light only so photos turn out a bit “off” in color…. …. however, by using a magenta filter in
fron of the lens, the overall lighting is more natural and “warm”.
Photographers must use filters to
correct those light sources back to “daylight” quality.
We will discuss this at length later
on. Right now just understand that it happens.
RED light rays only
contain red because it is a primary color. So GREEN
light rays only contain green, and BLUE rays
only contain blue. Again, that is because these are the
PRIMARY colors.
Secondary colors -
magenta,cyan, and
yellow are considered SECONDARY
colors because each one is a mix of two PRIMARY colors. Mixing PRIMARY &
SECONDARY colors will give you TERTIARY (third tier) colors …. making up all the visible
colors in the spectrum.
You can see how PRIMARY colors and SECONDARY colors mix from the chart below:
Do Not Worry….. there will be no
test on that. Just read it and think about it for a while.
Right now….. let’s go on
to LENSES
Love the site.. one correction though .. Yellow is primary color and green is secondary color (yellow and blue makes green)
Frank, glad that you like the site! What we’re talking about here is light rays. You are correct in that yellow and blue make green in the printing world. When you are using pigments or dyes to create different colors. This is commonly referred to as CMYK short for cyan, magenta, yellow, and key (black) color space. With light however the color space is Red Green Blue (RGB) to which the
primary colors are red, green, and blue.
This was new learning experience for me (about the definition of primary colours) and it helps explain a few definitions that previously i had trouble with. I love learning new things that challenge my previous concepts.
Thanks