Override default

Uses the settings from this window instead of the default settings for the recognition profile. The default settings are the values specified in the Recognition Profiles window.

Auto Set Threshold

The Administration module automatically calculates an appropriate threshold value for you. This function works by calculating the ratio of black to white pixels within the zone box you have drawn around the OMR shape. If that threshold value is exceeded, the OMR engine determines that the item has been marked. This button should only be used on unmarked OMR shapes on your sample page.

You can use this button as a calculator to determine a starting point for setting the threshold. Since the Auto Set Threshold button does not display in the Recognition Profiles window, you can take advantage of it here and then use the same value for the profile.

You can use the Auto Set Threshold button as a calculator:

• On the sample page, size your index zone so that there is only a small amount of space around the item.

• Only use Auto Set Threshold on items that are not marked.

• Note the automatically determined threshold value for a typical unmarked zone; you will need the value later.

• Try to make all the other OMR index zone boxes the same size as the one you used for determining the threshold.

• In the Recognition Profiles window, manually set the threshold for the other OMR index zones to the automatically determined threshold value that you noted above.

The preceding points ensure that a check mark causes the pixels to exceed the threshold.

Use the slider to manually select the pixel percentage threshold. If the percentage of black pixels (compared to total pixels in the zone) is above this limit, then the zone returns a marked value (the default is 1). Otherwise, it returns an unmarked value (the default is 0).

See Advanced OMR Settings window for more information on pixel percentage threshold calculations.