IBM 6400 Setup Manual page 329

Bar Code Quality
Determines the quality for graphics printing. Override Host must be enabled
to use these settings. Below are the values for non–rotated bar codes.
High. The default. Vertical is 144; horizontal is 120.
Low. Vertical is 72; horizontal is 60.
NOTE: The higher the resolution you select, the slower the print speed. When
selecting a resolution, try to balance the resolution quality your
application requires with how fast you want the print job to print.
Image Quality
Determines the quality for image printing. Override Host must be enabled to
use Image Quality. If Override Host is disabled, then the image is assumed to
be 144 by 144 and the image is printed at 120 by 144.
High. Accepts images with 120 by 144 and prints images 120 by 144.
With this setting, the image is printed as is and requires no conversion.
Because no conversion is required, there is more fidelity between the
original image and the printed image.
Low. The default. Accepts images with 144 by 144 and prints images at
120 by 144. With this setting, the image is converted from 144 by 144 to
120 by 144. Since there is some conversion required, there may be some
differences between the original image and the printed image. Review
the note below for more information.
NOTE: There is one bit of image data per pel. If your print job contains an image
created to print 144 by 144, which is very common for IBM 4234 printers,
some bits of data will be dropped out to support the best fit resolution,
which is 120 by 144.
When printing jobs with images created for an IBM 4234 printer, you will
want to print a few samples to ensure the results are satisfactory.
Appendix E. Code V, IGP, and IPDS Menus E–27