I picked up a book on Lightroom to work with the negatives. The book is "The Adobe Photoshop Lightroom 2 Book for Digital Photographers" by Scott Kelby. He pitched DNG when talking about importing pictures. He listed three advantages of DNG over RAW.


1) Each camera manufacturer has its own proprietary RAW file format. DNG was created by Adobe as an open format so that it can always be opened versus having an older proprietary RAS format abandoned leaving you potentially stranded when attempting to open an older format down the road.


2) DNG is generally 20% smaller in size than its RAW counterpart.


3) The Metadata is stored in a separate file (XMP sidecar file) with RAW. DNG packages the metadata for your picture with the DNG format. With RAW you'll always have to manage the RAW file itself and the XMP sidecar file that accompanies it.


Great book, BTW, if you have Lightroom and are needing a comprehensive tour.