Lights on and off
PERCEIVING COLOURS:
Colour is contextual
What happens to colours when we turn the lights off?
Details:
All ages
Time: 10 minutes
Learning Outcomes:
1. Recognize that the amount of light falling on an object impacts its colour appearance.
2. Notice that different colours become visible at different levels of illumination.
Colour Concepts:
1. We see colours in high levels of illumination; colours disappear in low levels of illumination; our cones function in high levels of illumination and our rods function in low levels of illumination.
2. Colours with higher lightness/value reflect more light. The lightness/value of a colour determines when it will be visible as levels of illumination increase. This makes the vivid yellow blocks appear first in this exercise, as light is slowly added to the visual scene.
Materials:
A selection of different coloured objects – e.g. red, green, blue and yellow coloured foam blocks, or vivid tiles from the sorting set. Try to include several hue families and a range from dark to light colours.
Flashlight (white)
White coloured paper
Sturdy surface for carrying objects (e.g. book, heavy cardboard)
A dark space
Instructions:
Figure 1. Images of coloured blocks under varying levels of illumination.
Place the white paper on a book or sturdy cardboard.
Arrange the objects on white paper and notice their colours.
Take the objects into a dark space, or turn off all the lights and close the blinds on the windows, or put the objects into a cardboard box with a hole for looking into the box and a hole with a slider to allow progressively more light into the box.*
Describe how going into a dark space affects the colours of your objects.
Slowly add light to your space. You can slowly open the door, or turn on your flashlight and first cover the light beam fully with your hand, and slowly remove your hand and gradually uncover the light beam. Notice and describe how the colours of your objects change.
Vocabulary:
Questions & observations:
What do you see in your dark space when all the lights are completely off? How does the appearance of the blocks change?
As light is added to your space:
How do the colours change as you add a source of light? Make sure to fully describe the colours with their hue family and character, or hue, lightness/value & chroma.
Which hue family do you see first?
How do the colours you see change as the light level changes?
Which colours appear first? Which colours are hardest to see in the dark?
Can you see colours in the dark? Explain why or why not.
What’s going on?
We see in colour when we experience levels of high illumination, like outside on a sunny day, or indoors in a fully lit room. When less and less light illuminates our surroundings, colours begin to disappear. In extremely low levels of illumination, colours can disappear altogether, and we perceive the world in greyscales.
When we experience colour vision, our cones receive light and activate our visual system. In low levels of illumination, our cones do not function as well, and our rods begin to work. This affects how we perceive colours. In extremely low levels of illumination, only our rods function and we perceive the world in greyscales.
Colours with higher lightness/value reflect more light. The lightness/value of a colour determines when it will be visible as levels of illumination increase. This makes the vivid yellow blocks appear first in this exercise, as light is slowly added to the visual scene.
Find out more:
See discussion on So how do we see all the colours in the world?
Examples:
Next Level Shoebox Variation:
Use flat black paint or black construction paper to cover the inside of the lid and the inside of the box.
Paint, or cover, the end of a paper towel tube black.
Cut a circular hole on at one end of the top of the box and insert a paper towel tube about 1”. Tape all around the hole to be sure no light gets in.
Cut a small ‘X’ (1/4”) into the top opposite the tube.
Cut a third hole, 1/2” diameter on the side of the box opposite the tube. Slip into that completely dark closet or room. Not a peek of light!
With a strong flashlight ask a friend to shine the light into the paper towel roll that is connected to the box while you peek inside through the small hole. What do you see? If you’ve done it correctly with no cracks or unpainted areas, you won’t see anything. You simply will not see a beam of light.
But when you lower a pencil into the box from the top ‘X’ hole you will see a pencil appear. Why? Because light now has something to shine on. It can’t shine on blackness, nothingness or emptiness. Light is like our eyes, eyes need something to see. If you’ve ever been in a completely dark environment you know how bizarre it feels to have your eyes wide open and see nothing.
