Film scanners are often claimed to be superior to flatbed scanners when scanning 35 mm films. The harder thing is to find actual facts supporting such claims. Actually it’s possible to find samples suggesting there is no significant difference between the scanners. And even Minolta was able to find the only relevant argument for film scanner superiority on their site: better optics.
The fact is that I was sometimes dissatisfied with a cheap flatbed Epson Perfection 2480 Photo scanner. I can compare its outputs with a dedicated film scanner (Nikon LS-40 / Coolscan IV) now. Indeed, there are significant differences in the results.
As for image quality I could observe the following:
- Every film defect (scratches, dust, garbage) is clearly visible in Nikon scans. Without digital ICE the Nikon scanner would be almost unusable. Epson is much better in this area and thus it’s the only option for scanning my old b&w negatives.
- The true resolution of the Nikon scanner is clearly superior to the Epson, despite their nominal resolutions are almost the same (2900 versus 2400 ppi).
- Nikon is much less prone to grain aliasing.
- Nikon output can be used without further processing, sometimes small level of USM improves the image. Epson output is very soft and typically requires strong USM followed by noise reduction and additional USM to get well looking results (but still somewhat inferior to unprocessed Nikon output).
- Epson suffers from irregular annoying stripes in monotone image areas, in the direction of scanning. This is one of the worst and completely unavoidable problems of the scanner.
- Nikon has shallow depth of field and the scan is often sharp in the center (the default focus point) and unsharp near the film field borders. Special care is needed to reduce the effect. Epson is much better in this area.
- Epson poor film holders make the scans prone to terrible reddish artifacts near the both ends of film stripes.
- There seems to be no relevant difference in the dynamic range capabilities of the scanners when scanning negatives.
To summarize: While one can often receive similar results from the scanners, there are situations where only the film scanner is able to produce good results. IMHO it’s really worth to consider investment into a dedicated film scanner instead of a cheap flatbed. On the other hand the flatbed scanner may be superior when scanning imperfect films when digital ICE can’t be used.
Besides the image quality convenience may also matter:
- Epson is much faster, I’d say I can scan a roll of film with it twice as faster than with Nikon.
- Nikon can load film stripes itself (some flatbeds can do that too). On the other hand it’s sometimes difficult to force it to move the film field to the desirable position so that it could be scanned whole, without cutting out any part of the film field area. I don’t know whether this is a problem of the scanner or of something else (driver? user?), but it’s annoying.
And finally, which low-end film scanner to buy? The cheap film scanners such as Plustek or Reflecta don’t seem to provide quality comparable to standard middle-range film scanners. A used Nikon LS-40 / Coolscan IV seems to offer very nice quality/price ratio for an advanced amateur. Older Nikons are SCSI devices, i.e. quite inconvenient to use with contemporary personal computers. Nikon LS-50 / Coolscan V is one of the rare middle-range film scanner models still in production. Minolta Dual scanners are cheap, but they don’t have Digital ICE (which makes their use very inconvenient), they seem to be more prone to grain aliasing and they are infamous for banding problems. If I understand the technology right, Nikon scanners are superior in their LED light source: It’s very reliable and there is no color interpolation (each pixel is scanned in all the color channels separately). Minolta Elite 5400 scanners look very nice but they are more expensive and the II model is known to be prone to defects. I don’t care about Canon scanners as they are completely unsupported in SANE. As for SANE support, AFAIK only Nikon LS-30 and LS-40 and Minolta Dual II and III are reported to be fully supported.
HTH, although it’s all mostly a personal opinion of course.