The page to be printed passes between inked rollers or plates four times, each time with a different coloured ink being used. In order to make sure that the final image is clear and sharp, the four printings must line up exactly on top of each other. This is known as registration. Registration marks, at the corners of a page, help the printer to position the images accurately. You may have seen a strip of coloured shapes on the edge of a printed food- packet. These also enable the printer to see at a glance if the four printings have been properly positioned.
Four color process printing uses four ink colors – Cyan, Magenta, Yellow and Black. These four colors are applied one after the other on a printing press. They overlap each other in various concentrations on the paper to create the visual effect we know as full color printing. Because these four colors combine to make an image, the proper registration of these colors is crucial to produce a sharp image. Even a slight position shift in one of the four colors will cause the printed image to appear blurred or fuzzy.
For the same reason as above, proper registration is also a concern for two-color and three-color printing. One-color printing is not concerned with ink registration since only one ink color is used (but like all printing jobs, the ink must be properly registered to the paper so that the image transfers to its intended location – i.e., not closer to one edge of the paper than intended).
A term related to ink registration is Close Registration, which means that the printed image has two or more ink colors that touch or are very near each other. By its nature, four color process printing always has close registration. Two-color and three-color printing may or may not have close registration, it just depends on the intended design. Jobs with close registration should be printed in a single pass through a printing press to ensure the ink colors align properly with each other.
Proper registration is also an important consideration for multi-part forms. Each ply of the form must be assembled in the same relative position so entries made on the top ply transfer properly to each subsequent ply. Have you ever filled out a multi-part form only to notice that what you wrote on the top was slightly out of position on a different ply? This is because the form’s ply-to-ply registration was off.
Picture Credit : Google