HP Officejet 350 All-in-One Printer - Manual (Page 172)

Resolution

Changing the Send Fax Quality
To modify the quality of outgoing faxes, follow the menu map below.
Remember, you can also modify the quality of faxes by selecting the
same options from the
OfficeJet Setup/Send Fax Quality menu in the
HP OfficeJet Manager.
Adjusting the Contrast
Normal
Lighten
Darken
Menu
Time/Date, Header
Reports
Fax/Copy Contrast
...
Adjusting the Resolution
Press the front panel Resolution button to change resolution. Refer to
chapter 2 to know which resolution settings to use in a given
situation.