Brother MFC-8820DN - Manual (Page 210)

13 - 14 HOW TO SCAN USING WINDOWS ®
4
In the Scan dialog box, click the Preview button. The entire
original will be scanned into the PC and will appear in the
scanning area.
5
Select the portion you want to scan by clicking the left mouse
button and dragging it over the area.
6
If you require advanced settings, click Picture Type from the
Adjust the quality of the scanned picture (C). You can select
Brightness, Contrast, Resolution and Advanced Properties.
Click the OK button after you choose your settings.
Scanning area
C