"OlegK" <oleglk@yahoo.com> wrote in message
news:8bc0611.0307082334.2c170f2d@posting.google.co m...
The only way is to manually increase exposure time. Auto exposure will limit
the exposure time to avoid over exposing the most transparent parts of the
film.

With Vuescan you could also crop an area without highlights, Preview, Lock
exposure, change the Crop to full image again, do another Preview for
colorbalancing and Scan. This will of course blow-out the highlights.

The problem is that the scene dynamic range as captured on film, probably
exceeds the dynamic range that the scanner can cover in a single exposure.
You can check that with the Density read-out (CTRL key + mouse hovering over
image) in the status bar when you check the preview of an automatic
exposure. The Highlights will have a density close to 0, the dark sky
probably more than 3.4

Bart