Epson CX6500 Reference Manual page 284

Note:
Make sure the document is flat against the glass surface; otherwise the image may
become out of focus.
An area of up to 2.5 mm from the edge of the document table glass cannot be
scanned.
1. Maximum unreadable area of 2.5 mm
2. Maximum unreadable area of 2.5 mm
Close the document cover gently so that the document does not
move.
Note:
To scan the document properly, close the document cover to prevent interference
from the external light.
Do not leave photographs on the document table for an extended period of time.
They may stick to the glass of the document table.
Do not place heavy objects on top of the CX6500.
For a thick or large document, you can remove the document cover to make it
easier to align the document. See
documents.
Removing the document cover for thick or large documents
Removing the document cover for thick or large