1. Colour Vision
Section 12.4

2. Colours red + green = yellow green + blue = cyan red + blue = magenta
Additive primary colours: red, green, and blue
Adding all three colours together will give white light
The light of two additive primary colours will produce a secondary colour
Secondary light colours: yellow, cyan, and magenta
Complementary Light Colours - Any two colours of light that produce white light when added together
magenta (red & blue) + green = white light
cyan (green & blue) + red = white light
yellow (red & green) + blue = white light
red + green = yellow
green + blue = cyan
red + blue = magenta

3. There are three types of cone cells in the retina of your eye that are sensitive to red light, to green light, and to blue light
Our eyes combine signals from these cones to construct all the other colours
How Our Eyes See
When light contains just blue wavelengths, we see it as blue because only the blue cones send signals
When light contains red and green wavelengths, we see it as yellow because the red and green cones send signals to our brain

5. Colour Vision
If, for example, you stare at a blue object for a long time, the sensitive-to-blue cones become tired so that if you then look at a white surface, which reflects white light containing all wavelengths, you see yellow (a combination of red and green – the cones that aren’t tired)

6. Colour Blindness Ishihara Color Vision Test
Colour Blindness is not blindness to colours, but is the inability to distinguish certain shades of colours clearly
Some cones may not respond to the light received
Red-Green Colour Blindness:
Difficulty distinguishing something red against a green background
Affects about 8% of males but only about 0.4% of females
Sometimes prevents a person from being able to do a certain job (Example. photographer, colour printer, airline pilot, ship’s officer)
Can sometimes be an advantage if a person is a hunter or soldier (can sometimes see prey against a confusing background more easily than other people)
Ishihara Color Vision Test
Everyone should see a 16.
Please note that these tests are not completely accurate as the LCD projector may alter the colours slightly.

7. Colour Blindness Tests2 5 42 7
57 or may see 35
10 or nothing