Have you ever looked really closely at a television or computer monitor? If you haven’t, take a magnifying glass or a small droplet of water and look at your computer monitor. Up close, you will see that your monitor screen is actually a series of red, green, and blue dots shining light at different intensities. When your computer displays an image, it takes the red intensity values from the image file and makes the red dots shine by those amounts. The ColorPicture program allows you to change which set of colors in the image file shine as which colors on the computer display—in other words change it so the red intensity values from the image file make the green dots or blue dots on the screen shine instead.
Part 1: Color Circles
Software to use: DigitalImageBasics with the Colors button active.
Open the picture Color Circles 1. Notice that the initial settings of the program have the same colors for “Color Measured by Camera” and “Displayed Color” (which is the color display on the computer monitor).
Describe the colors you see in this picture. What color is the circle at the top? On the left? On the right? What other colors do you see in the picture?
Change the combinations of “Color Measured by Camera” and “Displayed Color.” What happens to the circle at the top? Can you make the picture have only one yellow circle?
Part 2: Seeing One Color
Open the picture Sample: RGB Color Space. This is a picture where the edges of a cube span all the values of RGB colors. Notice how the colors in this picture are arranged. Imagine what things would look like if your eyes could only see one color.
What would this picture look like if we were blind to ALL colors except red—that is if we could see ONLY red light? How would the image look different in red than with all colors? Move your mouse over the picture to see the red intensity values of pixels throughout the image.
Change the view of this picture so that you can only see the red intensity values of the image file. To do this, set all three “Color Measured by Camera” choices to ‘Red’. What areas look bright in red light? Which areas look dark? You can also try settng the Blue and Green values to “None”.
Now view the picture with only the blue light. How does the picture look different? What details can you see better in the blue light? What is visible in the red light?
When all of the computer display colors show the red picture color, why does the image appear black and white? If your eyes were only able to see red, do you think that is what the world would look like?
Colors of the Sky
Open the picture AllSky.jpg. This is a picture of the sky using a camera with a fish-eye lens, which allows most of the sky to be seen at once. This picture is courtesy of Chuck Wilcox at the Museum of Science, Boston, Massachusetts.
Now that you have learned so much about color and light, get to know the colors in this picture. Move your mouse around the image and notice the color intensity values throughout the picture. Change which picture colors are seen in the computer display colors.
Which of the three-color components (red, green, or blue) is dominant in the sky? Which color contributes the least intensity to the sky? See the contribution of a color by setting all of the computer display colors to a single picture color.
If the sky is blue because of tiny atmospheric particles scattering blue light, why is the Sun yellow? Hint: this is a good time to take a look back at the Tri-Color Reference Chart that you created in Part 1.
If the Sun appears to be yellow, why do clouds appear so white in the image? If you were riding on a satellite thousands of miles above the Earth, what would be the color of the “sky” (or outer space) and what would be the color of sunlight?
Open the picture sunset.jpg. This is a picture of the Sun setting over the ocean. Here the sky is yellow and orange while the clouds are dark. Use the ColorPicture program to get to know the colors in this picture.
Why is the color of the sky different at sunset from the middle of the day? What about the clouds and the Sun?
What color is the dominant color of the water? Where is the blue in this picture?