HP Deskjet 5850 Color Inkjet Printer - Manual (Page 152)

automatic paper-type sensor
The Automatic Paper-Type Sensor automatically selects the print settings appropriate
for the media being printed on, particularly when used with HP paper and media.
When the Automatic Paper-Type Sensor is engaged, the printer scans the first page
of a document with a blue optical sensor light to determine the best paper-type
setting. Once the paper-type setting is determined, the page is printed.
For information about using the Automatic Paper-Type Sensor, click here .
The Automatic Paper-Type Sensor is not available for documents
printed from the
250-Sheet Plain Paper Tray Accessory .
Do not place the printer in direct sunlight. Direct sunlight can
interfere with the Automatic Paper-Type Sensor.