From within ScanGear, click the Preferences button at the bottom. Note: While the screenshot below shows "Basic Mode", the Preferences button can also be accessed from "Advanced Mode" and "Auto Scan Mode" as well.
On the "Scanner" tab, the Calibration options can be found. Click Execute to begin the calibration process.
The calibration process may last anywhere from 1 to 2 minutes.
When the above window disappears from the screen, then the calibration is complete.
Repeat the calibration up to 3 times if the desired results are not achieved.