I.R.I.S. Readiris 14 for Windows User Guide - Manual (Page 114)

Readiris TM 14 – User Guide
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Note: when you select an output format or application that does not
support images, then the Graphics Options will be unavailable in
Readiris.
Below you find a description of what each option does.

Black-and-white images
Readiris by default saves images in color. Select this option to
generate black-and-white images. The colors of the text inside
your documents can still be maintained.

Maintain scan resolution
This option is activated by default. Readiris generates the output
documents in the same resolution as your scanned documents.
To verify in which resolution your documents have been
scanned, check the Scanner Settings. Or check the image
properties in the interface.

Reduce resolution to:
If you don't want to maintain the original scan resolution, then
select the option Reduce resolution to, and indicate to which
resolution you want to reduce the images;
Note: it is recommended to use a resolution of at least 72dpi.