In order to reproduce continuous tone images, such as a photograph, on digital equipment, the image is divided into various sized spots. The "spot" is often confused with the "dot" as in "dots per inch", but a printed dot is actually made up of a group of spots. It is common to refer to the resolution of an output device as dots per inch (dpi), even though it actually means spots per inch. In digital terms, a dot (group of spots) is made up of a grid of bits. A bit is the smallest unit of digital information and is represented by either a zero or a one (either on or off). A grid of bits is called a bitmap. Groups of dots are used to create halftone images, which are used to represent continuous tone images, such as photographs, in a printed form.

"Line screen", "line frequency", "screen frequency", or "screen ruling" are terms applied to the lines of dots in the halftone screens which must be used to create the image that is being printed. A line screen contains a designated number of lines per inch (lpi) comprised of dots, which are used to create the print resolution of the desired image. "Dots" has become the generic term applied to all of the dot structures used to create the halftone, regardless of whether the dot shape is square or elliptical. When making an image into a halftone, only one type of dot structure is selected to be used for screen conversion.

Consider the following when producing halftone images:

• If the image is to be scanned into a computer, then the scanner or computer can apply a screen to the digitally created image.
  
  
• If the image is provided as a continuous tone original from a camera, then an acetate film (contact) screen is placed over a halftone negative. Light exposes the film as it passes through the dot pattern to create the halftone negative. The resulting film negative is then used to burn the image into a plate.

The rows of dots on the screens used for each of the four colors (cyan, magenta, yellow, and black) necessary for color printing must be positioned at a specific angle so that the printed dots do not form a distracting pattern. The angles are: 45 degrees for black, 75 degrees for magenta, 90 degrees for yellow, and 105 degrees for cyan. The angles form a rosette pattern which is merged into one continuous tone by the human eye.

If bitmap text is scaled up to a much larger size, the characters may have a jagged appearance because the individual spots or pixels become much more visible. Anti-aliasing partially fills in or blurs hard edges, to help make the edges on text characters appear to be smoother like those of outline type. If anti-aliasing is used on very small fonts or point sizes, the resulting text can look blurry and be very difficult to read. Another point to remember is that the processing and printing time resulting from anti-aliasing may increase by as much as 30%.

Trapping can help compensate for registration problems by slightly expanding one color into another and eliminating the gaps and color shifts between colors. Because poor registration of colors is rarely a problem with digital printing equipment, trapping is usually not an issue, but it is important to understand how it works. For trapping to be effective, it must compensate for less than perfect registration without forming noticeable lines of unrelated color around objects caused by the overprint. Process colors that share a sufficient percentage of common colors do not require trapping, because any registration problems will reveal a color that is similar to each of the adjacent colors. An example of where trapping would not be necessary would be a printed item containing mostly reds and oranges. If the object on such a page were not in perfect register, the result would not be visually distracting because the colors in the gaps and overprinted areas would be similar to any adjacent colors.

Selecting the best paper for a digital print job can be critical to the success of the application. Paper must be selected not only because of how it relates to the design of the application, but also because of how it will run through digital equipment and because of the differences in toner technology and traditional printing inks. Output problems such as halos and mottling can be avoided if careful attention is given in selecting the best paper for the job. Duplexed applications (jobs with printing on the front and the back side of the sheet) may look awful if printed on paper that allows the print to show through the paper. A heavier weight paper or a paper with a higher opacity would be the best choice. The finish of the paper should also be considered because toner will have a different appearance than traditional ink on the same paper.