Why different scan results when scanning through computer and through Sane (on openwrt)? Scanner HP ScanJet 3500c?

Question

Arduino

Decided to make the scanner (HP ScanJet 3500c) available to all computers in the house. I installed SANE on my wr1043nd router, where OpenWrt (Attitude Adjustment 12.09) is installed ( this instruction helped a lot ), and tried to scan using the SaneTwain program. The result was unexpected, some overly contrasting and not bright image turned out:

At the same time, when the scanner is connected (with the same cord) to the computer and scanned using standard Windows tools, the result is quite suitable: The computer

from which the scan is performed is Win7 x64 Ultimate.
What am I doing wrong?

Answer 1

Have you tried scanning A4? (not bills)

Answer 2

Copy protection of banknotes and various documents with seals and watermarks.

Answer 3

I propose to download Ubuntu on your computer (at least from a USB flash drive) and try to scan from there. So it will be possible to conclude whether the sane driver is to blame in general or a glitch in the assembly under openwrt.

Answer 4

This problem is typical for weak USB ports.