Kodak i800 Series User Manual page 113

Background Value this value will be substituted in the grayscale
(pre-thresholded) image for the color being removed. Therefore, this
value should be higher than the threshold value selected on the Scanner
Settings dialog box for this pixel to become the background color. The
default value is 160. For example, if you are scanning a white document
with a green form and you have selected a binary threshold value of 127.
You should pick an electronic color dropout background value greater
than 127 so the substituted pixel will be white in the dropped-out image.
Threshold value the value that is used to identify the color which will
be dropped out. This value is applied to the color space. The default
value is 155.
A-61510 January 2005 4-32