Making Color Mash-Ups

Light is one heavy subject.

You're told that the primary colors in painting are red, yellow, and blue, but then you learn that the cones in our eyes only sense red, green, and blue. All light together makes white light, but all color paint together make brown and black. What gives?

The science of colored light is incredible, and there's so much to learn. I was fascinated by a particular project called "Three Little Pigments" at the Exploratorium, where you can explore pigments and light color with printing on transparencies. They have a great explanation of the science in this project. In it, you have four separate transparent sheets, and when you combine them and hold them up to a light, it becomes a recognizable image. Watching the colors combine is absolutely magical. And optically scientific.

In the project, you can only use their pre-made landscape, but I wanted to show how you can turn any image in to this project to make a wonderful investigation have a locally meaningful picture behind it. And now, here's how!

• What: Making Color Mash-Ups
• Time: ~30 minutes to make
• Cost: ~$2, depending on print size
• Concepts: light, color, perception, pigments, wavelength
• Materials:
  • Transparencies (laser or ink depending on your printer)
  • Color Printer
• Tools:
  • Photoshop or GMP (free version)

Let us alight!

Let's start by separating out our document to the CMYK colors.

1. Open the document in Photoshop, and go to Image > Mode > CMYK color.

2. Go to the layers panel, and see each one in black and white form.

3. On the Channels box, click on options and select "Split Channels."

A science explainer:

While light contains a huge myriad of colors, we just sense three. Compare that to the mantis shrimp, which can see sixteen! We see red, green, and blue light, and when we combine those we get the secondary colors: cyan, magenta, yellow, and black. These are the colors that our printers use as well.

When we have a part of the picture with cyan, it blocks out red light. When we have magenta, it blocks out green light. For yellow, it blocks out blue light. The "K" in CMYK is simply black, which is used for adding dark detail without having to saturate with each color.

Each color is now in its own document, but they appear in black and white. Wherever the part of the picture that has a heavy amount of that type of ink is represented as black. Let's change them to their colors.

In photoshop:

1. Starting with the "Magneta" document, go to Image > Mode > Duotone.

2. Click on the color box, and go to the right and set C = 0, M = 100, Y = 0, K = 0.

3. Repeat the process for the other three pigments, except for each make that color value = 100 and the rest = 0.

4. Save each as a separate PDF.

Now we have four documents each with the pigment and its appropriate color. You can notice some predictable things like there is not much yellow pigment in the sky, because that would block out blue light. Look around. What surprises you?

Load up a printer with transparencies. Much sure you have the right ink vs. laser type, and print away! You'll get four versions of the same image, but with each of the pigments individually. This is what a newspaper or a screen printer does, similar to this!

Re-combine the images and hold up to white light see through them all. It's our original photo again with even a slightly neat 3D look. What happens when you take one of the pigments out? What does it change?

Try messing around with different types of image, different colors, to learn more about the way our vision and colors of light work. If you're feeling really advanced, try out the CMYK Holiday Card, too!

Have fun, see some color, and keep exploring!

Can't wait to see what you make and share!