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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!

Step 1: Separate the Colors

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.

<p>Very good ible. I made one of these about 8 years ago, A Rose, for my wife. This brings back memories. :-) </p>
<p>This is a great, simple project that has a very interesting and engaging outcome. Thanks for the detailed instructions.</p><p>Lauri</p>
<p>Nice work! Gives me lots of ideas.</p>

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Bio: The Oakland Toy Lab is a community-based wonder lab for students to build, tinker, explore, make, break, and learn! We are writing up engaging science ... More »
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