Brother MFC-3420C - Manual (Page 34)

2 - 5 HOW TO SCAN USING WINDOWS ®
Pre-Scanning to crop a portion you want to scan
The PreScan button is used to preview an image for cropping any
unwanted areas from the image. When you are satisfied with the
preview, click the Start button in the scanner window to scan the
image.
1
Load your original.
2
Select the settings for Image Type, Resolution, Scan Type,
Brightness, Contrast and Document Size, as needed.
3
In the Scanner Setup dialog box, click the PreScan button.
The entire original will be scanned into the PC and will appear
in the Scanning Area.
Scanning area
Scanning area