This section will help a potential buyer make his/her own opinion about the scanner basing on the scans it actually made. And first let’s check how good the CanoScan 8400F is at removing dust from photographs. I turned on the Reduce Dust and Scratches option in the scanner driver for that.
I performed a series of tests to see how well the dust removal technology works with reflective originals, i.e. ordinary photographs (as you understand, there’s no sense to remove dust from a scan of a glossy magazine). The originals were scanned at different resolutions and in all the available dust removal modes (Low, Medium, High) and I came to the conclusion that the technology works best at medium resolutions (up to 600dpi) whereas at higher optical resolutions dust is not removed completely. Here are the fragments of scans digitized at 600dpi and scaled up in Photoshop by 300%:
Original photo with the marked image fragment
The different modes help you choose between speed and quality. Of course, High mode brings you the best quality, yet Low mode effectively removes all the small dust specks, too.
It’s somewhat worse with films. FARE technology depends on the type of film, cannot work with negatives (and Digital ICE cannot, either), and often makes small artifacts more conspicuous by mistake. Below you can see a scan made without FARE (left) and a scan with FARE in High mode (right):
On one hand, FARE removed the dust speck (and I should acknowledge that it did a good job of the whole scan, removing quite a lot of such small artifacts), but it also brought about its own artifacts. Well, I think it’s anyway easier to remove manually one artifact than to do the retouching of a whole image. It’s just a matter of what you prefer to do with your own hands.