Epson Expression 1680 Reference Manual page 77

When scanning transparencies, store the reflective document
mat in the Transparency Unit pocket.
c
You are now ready to scan the film strips using your scanner
software.
Note:
Make sure to select TPU for Neg. film or TPU for Pos. film as the
Document Source setting in EPSON TWAIN Pro.
When TPU for Neg. film or TPU for Pos. film is selected as the
Document Source setting, the focus position is automatically set to
2.5 to accommodate the use of the film holders.
Mounted slides
1. Load slides in the 35-mm slide holder face down, as shown
below. Repeat this step for all the slides you scan.
4-8
Options
Caution:
Do not put anything but the reflective document mat into
the Transparency Unit pocket.