Archived from groups: rec.photo.digital (More info?
They hold the slides straight, making it easier for the scanner software
to auto-detect the thumbnails. If your slides are unmounted, they
also keep the film above the scanner glass surface, avoiding Newton's
Rings. This is not necessary for mounted slides as the mounts maintain
"timeOday" <timeOday-UNspam@theknack.net> wrote in message
> I've never seen one and am wondering if I could get by scanning a few
> slides without one. What do they do? Backlight the image? Surely they
> don't just hold the picture straight.