>When I scan as "Raw" with the dust filter active, I end up with an
>Alpha channel in Photoshop with all of the dust and scratches. How do
>I use this to clean the RGB image?
You don't. You tick the checkbox for the infrared filter in Vuescan and
save the output as an RGB not RGBI file. Vuescan does the cleaning.
Rob Geraghty firstname.lastname@example.org