Analog Digital Images

Sheamol Obeda

Digital images are all just spreadsheets with layers of red, green and blue stacked on top of each other. Every image you see on a screen, from your laptop to your phone to your TV, are made with layers of pixels. When you take a photo, your camera measures the amount of red, green, and blue light reaching each sensor and a number between 0 and 255 is recorded for each pixel. There are 16,777,216 different colors available, each using only 8 bits per color. With more pixels per inch, a higher quality image can be made. Most screens use liquid crystal displays, in which the red, green and blue light is arranged into blocks and the brightness of each segment depends on how much red/green/blue needs to be displayed. All of this can be done at home without the use of a computer screen!

What is color?

All of the observable colors to the human eye can be made using the three primary colors: red, green and blue (note that these are the primary colors for light and are different from the primary colors of pigment). This is because different amounts and combinations of these three colors portray different colors. For example, one part red to two parts blue makes a lilac color. There are many more colors, but humans can only see a mixture of the three primary colors because humans only have three types of cones in their eyes. Each cone measures either red, green or blue, and then a clear image can be constructed by the brain. Color blindness occurs when one or more of these cones doesn’t function fully, so one color may not be properly seen. For example, someone may have difficulty differentiating between shades of blue.

To easily see how different colors are made from combinations of the three primaries, a color spectrum can be used. The midway between red and green is yellow. Thus, yellow is one of the secondary colors and is made from a mixture of red and green light. Cyan is midway between blue and green. The color magenta gives us some problems. All of the other colors can clearly be seen as a sum of wavelengths of light. However, the midpoint between red and blue on the color spectrum is green. Since green is a secondary color and there is no green light hitting the cones of our eyes when we’re seeing the midpoint between red and blue, the brain creates a new color which isn’t really there. This color is magenta.

Back to the screen

To show how an LCD screen works, a group of scientists and volunteers at Manchester Science Festival in 2016 recreated a digital image using only sheets of plastic and pens. Each sheet of plastic had three numbers on it, denoting the percentage of red, green and blue needed, along with an X and Y coordinate. 8000 pixels later, a final, 10-meter tall image was created! An 8cm square is split into three sections. Each section is colored in according to the RGB proportion needed for that pixel. This pixel is then put in the correct position, and, after a week of work, you finally have your own analog-digital image!

Yes, I know what you’re thinking, “how am I going to get a 10-meter tall window to use?” But don’t worry, you can still make a smaller image using the exact same method: all you need is three pens and a few sheets of acetate. By following the procedure above you can get the same result.

Mini MegaPixel

“But I’m too lazy, I don’t want to move!” Well, there is another solution to this problem. Matt Parker has created a program that can convert each pixel in an image to a red, green and blue value, and plot this as a spreadsheet, just as a computer screen would do! Heres the link if you’d like to give it a go.

http://www.think-maths.co.uk/spreadsheet

Edited by: Kaylynn Crawford, Ruby Halfacre, and Karen Yung