Jacques Cousteau in Seashells

• A black-and-white photograph or picture of a simple, easily recognizable scene or person
• Graph paper with 1/4-inch (or 1/2-cm) squares
• Paper clips
• A pencil

For this activity, you can use the pattern of dots supplied below (click on the image to enlarge it) or make your own dot pattern.

To make your own dot pattern:

1. Place a sheet of graph paper on top of your picture.
2. Clip the picture to the graph paper so it doesn’t move while you’re drawing.
3. Pick any square to start with.
4. Notice that dark portions of the photo show through the graph paper. Estimate what portion of your chosen square is black, then draw a black dot whose size corresponds to the percentage of black you estimate is in the square: The more black in the square, the bigger your dot (click to enlarge diagram below). If the square is not black but rather some shade of gray, the size of the dot will depend on how dark the gray is. In a square filled with pale gray, put a small dot; in a square filled with dark gray, put a bigger dot.
   
5. Repeat the process with each square in the picture until you are finished.

When you’re done with your dot picture, hold it at arm’s length. If the dot picture is of a familiar object, it should be easily recognizable at this distance. See if other people can identify the object in the picture.

For simplicity, we’ve used a picture of an eye as a sample here. Unfamiliar or complicated objects may be more difficult to recognize at close range.

Place the picture across the room, and you’ll notice that it becomes much easier to recognize. The dots will seem to disappear, with only the pattern remaining. The picture may appear slightly fuzzy, but it certainly doesn’t appear to be made of dots!

Pictures made of dots are easily recognized by the brain because the brain is always attempting to interpret what it sees. Even though our sample picture is made up of different-sized dots, the brain recognizes the overall shape as that of an eye, since it is very familiar with that shape. This is the same reason you may see shapes in clouds, inkblots, or even pieces of toast. Your brain does not merely register these shapes as abstract patterns, it attempts to interpret them based on previous experience.

The dots disappear when you view the picture from a distance because of the limited resolving power of your eyes. You see the dot picture because light reflecting from the page makes an image on the retina of your eye. This image stimulates the light-sensitive cells in the retina and your brain interprets the result. When you move the dot picture farther away from your eye, the image the picture makes on your retina becomes smaller. The images of the dots overlap on the light-sensitive cells. Unable to distinguish between adjacent dots, your eye perceives shades of gray, rather than black dots and white spaces.

To print shades of gray using black ink on white paper, printers use halftone reproduction. The phenomenon of the “disappearing” dots is the basis of these halftones. A magnifying glass will show you that printed photos in newspapers, books, and magazines are actually composed of thousands of tiny dots, often too small for the eye to separate.

Artists in the late nineteenth century, taking advantage of this phenomenon, created a style called Pointillism. Paintings in this style—most notably those by Georges Seurat (1859–1891)—are made up of thousands of tiny dots of brilliant color which, at a distance, merge in the beholder’s eye.

The images on a computer monitor, tablet, or smartphone are also made up of dots. If you put a drop of water on a tablet or smartphone, it acts as a magnifier so you can see the dots. Your eye blends these dots to make a picture.