Why part of the scanned image is brighter than the original?
When you scan documents where the ScanSnap or document is exposed to strong light such as sunlight, part of the scanned image may be brighter than the original document. In that case, keep the ScanSnap or document away from the strong light and scan.
Furthermore, depends on the type of the document, such as glossy paper, paper with a black edge top, curled paper, the image on the edge top may be brighter than the original document. In that case, place the document away from the ScanSnap so that the document can avoid the reflected light from the side of the ScanSnap.
When the document is in contact with ScanSnap (circled in red):
When the document is placed away from the ScanSnap (circled in red):