Color Blindness

Overview: The primary colors for light are red, green, and blue. A normal eye has cones of all three colors. Different types of color blindness occur when the eye is missing one of the colored cones.
​​Supplies: LED image box, various color palate images including Ishihara Test images, gel sheets
Objectives: Understanding of additive color mixing, subtractive color mixing and what different types of color blindness look like.

Setup:

  • Setup the picture box with your choice of LED light
  • Choose a picture to start with, whether it is the stop light picture, the Monet picture, or an Ishihara Test image
  • Changing the LED color combinations simulates additive color mixing
  • Placing a gel film over the glass of the box simulates subtractive color mixing

How to run the demo:

  • Place an object or print inside the box that has distinct color information (artwork, color plate tests, stop light image)
  • Choose an LED color to illuminate the box using the LED remote control, remote pointed at the control IR sensor.
    • For white light: W button
    • For pure color: R, G, B color buttons
    • For two color mixes:
      • RG – Orange
      • RB – Purple
      • GB – Teal
  •  Choose a gel film to filter out a desired color of light

Get familiar with the gel film colors and their possible combinations with white light LEDs (composed of RGB LED superpositions):

Single Gels: to demonstrate color filtering

  • Red Gel – passes R
  • Blue Gel – passes B
  • Green Gel – passes G
  • Purple Gel – passes R,B – Yellow Gel – passes R,G
  • Orange Gel – passes preferentially R, some G
  • Pink Gel – passes preferentially R, some of BG
  • “Fluorescent” Yellow Gel – passes R,G

Gel Mixes: to demonstrate subtractive mixing

  • Red + Yellow Gel – Passes R
  • Red + Purple – Passes R
  • Purple + Yellow Gel – Passes R

Non-Overlap combinations – Should be mostly dark Detailed

What’s Happening?

There are several colors of gel films that can be layered on top of the glass viewing portion of the box to simulate subtractive color mixing. Any LED light color (different combinations of RGB outputs) can be used without the gel films to show additive color mixing. For example, white light can be set to the LEDs with a picture/object in the box that contains distinct primary RGB information (additive color mixing). A red, blue, or green gel film can then be placed over the glass viewing portion of the box to isolate that color from the LEDS (subtractive color mixing). Furthermore, if the LEDs are lit with 100% red light, a green or blue gel film can be placed on the glass viewing portion to see that no red light information is passed through.

With control over component LEDs and color gels, the color box allows us to explore types of color blindness. For example, using one of our art prints, we can show how lack of red suppresses the impact of red flowers among green grass. In our box we would use the Monet image with only Blue and Green LEDs active. Using the Ishihara color blindness test plates, we can cycle through each primary color or primary gel to test which colors the “test” is for. For example, if we only see a number when the R LED is illuminated, we know that the plate is testing for red colorblindness, as the image will be invisible without registering red. After cycling through primary colors, a demonstrator would use the two-LED color options to show a more realistic view of what a color blind individual would see.

For a more complete look at what different LED color combinations and gel sheets do, visit this document.

Ask this:

  • How do the filters explain what we saw in the light color mixing?
  • How do the single color LEDs act like the previously used filters?
  • Can we use what we know about single color results to predict the multiple color results?
  • What kind of color blindness do each of these combinations test for?

Learn more: (external links)