Correcting Posterization

Obvious "stair-stepping," or sudden shifts in tones, rather than smooth transitions in areas of tonal gradation (see left half of figure), is called Posterization. It results because of a lack of available gray levels. The number of gray levels is determined by the number of dots in a halftone cell.

To correct posterization:

If you are copying or scanning a halftoned or photographic image, and getting posterized output, try the following:

1. Click Copy Services, then click the Image Quality tab.
2. In the Original Type dropdown menu, make sure Mixed Text and Graphics is not selected.
3. If satisfied with settings, click the <Copy> button.

Other options include:

Scan at a higher resolution.

Select a Original Mode with low contrast.

or

Use the Contrast Control to lower the contrast.

For more details about posterization, see About Posterization and Gray Levels.

TIP: If you have programmed and run a job, and received unexpected results, ensure that the system-wide settings are all set back to their defaults by clicking <Clear All> or <Reset> in the user interface. Then proceed to do job programming pertinent to your job.