Originally posted by Macario actually, the loss in quality is minimal. I have the Konica Minolta dual scan 4. Not the most expensive scanner (and the dust and scratch removing doesn't really work on this model), but the results are fantastic. Very sharp pics when scanned, and it is much easier to produce a nice pic in b&w than with a digital camera.
The Dimage Dual Scan IV and 5400 are both excellent scanners and would be my choice if I were looking for value on the used marketplace. They were direct competition to the Nikon Coolscan models during the time when they were made.
As for the loss of quality...Now there is a concept. The Dual Scan IV will give most optical enlargers, even those with quality optics, a real challenge. The best way of thinking about the Minolta and Nikon dedicated scanners is that they are a microscope attached to a sensor array.
Steve