Last month we looked at paper. This month we put paper under the microscope again, but this time we will look at the printing on the paper.
Here is a stamp from a postcard I received recently. Looking at the picture under a magnifier at higher and higher magnifications we can see that the colors in the stamp are not as uniform as they appear when we look directly at the stamp. It is actually made up of lots of tiny little dots of color.
On the left is a slightly magnified image from a magazine. It is actually a picture of a digital camera, and you can see some of the buttons and connectors. Even at this relatively low magnification you can see that the colors are not solid, but have a spotty texture. At even higher magnification (on the right) we can see that the image - in this case the button in the middle of the previous picture - is actually made up of a regular array of small color dots. The dots in magazines and newspapers tend to be rather large, and are easy to see under a magnifying glass. The dots on pictures on large advertizing billboards are even larger and can often be seen with your unaided eye.
On higher quality images, where the picture has to show more detail, or a larger range of colors, then the dots tend to be smaller or closer together (or both). The image on the left is part of a postcard that has been magnified by about the same amount as the magazine picture you just looked at. It is harder to see the dots, (although they are still there, as you can see in the higher magnification image on the right) so the image looks much clearer, and seems to have a greater range of colors. The postcard is actually a greatly magnified picture of a single grain of pollen, and this image is just a small part of the surface of that grain! This shows why the dots of colors work. If the dots are so small that your eye cannot resolve the individual dots, then they all blur together and our brain interprets the image as a solid area of color. The actual color we see will depend on how much of the different primary colors are present in the dots that have blurred together in that area. This idea that you can create many different colors by having small dots of a few basic colors is not new. Impressionist painters such as Monet have used this idea to create many wonderful paintings.
Not all printing is composed of discrete dots. Here are two examples that are not. On the left is a magnified piece of printing from a laser printer. The printing is formed by many very small particles of toner which have been fused together to form a continuous black stain on the paper. Another way to "stain" the paper is with ink. The check mark on the right shows what ink on paper looks like at high magnification. The liquid ink thens to bleed slightly into the fiber of the paper. This makes the edges of lines (which look perfectly straight to the unaided eye) have a raggedy appearance under the microscope.
There are many other sorts of printed material you can look at under the microscope. Why not try and find a few. Try looking at a dollar bill, or the signature line from a check
Not all pictures are printed. Here is a photograph of a person. Actually it is a photo of me at my brothers wedding; I don't usually dress quite this well. The magnified view of my glasses on the right shows the same sort of spotty texture as the printed images. This time the color spots are formed by grains of chemicals in the photographic paper. Each grain is a different color, and the size and number of each colored grain in any area depended in the color and intensity of the image in that spot on the photograph.
Have a look at other images you find - pictures on cereal boxes, junk mail, birthday cards - and see how they are made.
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Last Update: 10/25/97