Brother MFC-8640D - Manual (Page 158)

USING YOUR MACHINE WITH A MACINTOSH ® 7 - 43
Scan to File:
In the General tab
You can enter up to 30 characters in the Name for Custom field.
This name will appear as the button name.
Select the type of scan from the Scan Action field.
In the Settings tab
Select the file format from the File Type pull down list. You can either
send the file to the default My pictures folder or select your own
destination folder by using the Browse button.
You can also select Resolution, Scan Type, Document Size,
Brightness and Contrast settings.