Pictures on a computer screen are made up of thousands of tiny dots, known as pixels (short for picture element). Depending on the size of the dots, a different number of dots can fit on a computer screen. If the dots are small, a large number will fit on the screen. However, if the dots are large, it takes just a few dots to fill the whole screen. The more dots on the screen, the clearer the picture will be.
How many dots?
The word "resolution" describes the number of dots that make up an image. A high-resolution image is made up of a large number of tiny dots. High-resolution images are very clear and show a lot of detail. A low-resolution image is made up of fewer, larger dots, so the picture is less clear. By making the dots smaller, we can see smaller things in the picture, but we need more dots to cover the same picture. It takes more space and time inside the computer to keep track of more dots.
The color depth describes the number of colors that are used in a digital picture. As the color depth increases, the picture of the two boys playing becomes more lifelike.
In the 2-color picture, each pixel can only be black or white, making the image difficult to interpret, especially at lower resolutions.
With 256 colors, each pixel can be any one of 256 colors. It might seem that 256 colors is a lot, but most photographs are made up of many more colors than this. Limiting the colors to 256 usually means losing some image detail.
With millions of colors, the picture has the highest color depth. The picture is very lifelike as it is closest to how we see things in the real world.
Why doesn't everyone use millions of colors? It takes your computer longer to handle all those colors. You choose either better detail, or less time.
More things to try
If you can find a magnifying glass, use it to look at this computer screen. Can you see the dots? How many colors can you count?
Find a newspaper or magazine with pictures in it, and hold the magnifying glass up to it. Can you see the dots? How many different colors are there?
Make a pixel picture! Try coloring a picture using dots. Copy a picture on this page or make one up for yourself! How does it look if you use big dots? How about small dots?
The first person to make pictures out of dots was George Seurat. He made paintings out of nothing but tiny dots of color. Here is one of his paintings, The Parade. In this magnified piece of the painting, you can see the tiny dots of color Seurat used to make the picture.
Can you see the dots in the painting? Lichtenstein produced art that looked machine- like. He used a technique called "Ben Day dots" to create effects similar to those seen in low-resolution computer images. The technique was invented by Benjamin Day in 1879, many years before computers were around! We still use the same technique today in printing newspapers and magazines!
To learn more about Georges Seurat, Roy Lichtenstein and see more of their paintings, try these web sites: