Scanning microfiche?

Tim wrote: Yup, standard magnifications are 24, 42, and 48. It's worse than that. The high resolutions they quote are *interpolated*. Usually the real resolution (which they call "optical resolution") is no more than 600 DPI, or sometimes even 300. A few scanners can do 1200 DPI optical on one axis. Talk to Al Kossow. Having looked at a lot of DEC field service fiche, I didn't expect that anything under 300 DPI effective would even be reasonable to look at, much less to OCR. He thought 200 DPI effective might be OK. He sent a few samples off to a service bureau in southern CA, and they scanned them at several effective resolutions including 200 and 300 DPI. The 200 DPI scans were basically worthless. The conclusion was that it really needed *400* DPI effective. If you save greyscale data, 200 or 300 DPI effective might be OK. But greyscale doesn't compress anywhere near as well as bilevel (using either Group 4 fax compression [*], or JBIG [**]). The service bureau charges around $0.07 per page (not per sheet of fiche) to do this. They seem to miss a lot of pages in the process, so I assume that they do NOT use a method that scans the entire fiche, but rather a step-and-repeat sort of process. Canon makes a fiche viewer/scanner for about $10K: http://www.usa.canon.com/corpoffice/imagefilingsystems/ms800.html I've seen a similar product from another company, but it was a bolt-on attachment to a user-supplied fiche viewer, and it still cost about $10K. For that money I'd rather have the Canon since it was designed from the ground up to be a scanner. The only way to do a good job of it in bulk would be a drum scanner with a resolution of at least 14400 DPI (300 DPI effective), and preferrably near 19200 DPI (400 DPI effective). I've seen 15000 DPI drum scanners for around $50,000; I've never found any that can do 15000 DPI. Not many. A lot of them use the SCSI 2 scanner commands, but with undocumented extensions. High end professional scanners usually have a dedicated PCI interface card. Eric [*] The nice thing about G4 is that not only does it do very good compression, but it's also lossless, so it doesn't have unpleasant fringing and smearing effects like JPEG. I still can't believe that people try to use JPEG for text and line art, it's a bloody STUPID thing to do. JPEG is designed for CONTINUOUS TONE IMAGES. Oh well, don't get me started on that, I could rant for hours. The bad news about G4 is that most people don't have software that can process raw G4 files, or TIFF Class F G4 files. People will try to claim that your TIFF files are broken. The good news is that G4 is a native Acrobat compression format, so you can supply PDF files that will work for everyone. That's how I supply all my scanned documents now. I still get complaints from a few people that they can't read my PDF files on their PDP-11/05 or Commodore 64. I ignore those people. I like old computers as much as anyone, but I don't expect to view 300 DPI scanned images on a computer with 64K of RAM and a low resolution display. I have more modern computers for that. [**] JBIG is also lossless and typically compresses 10-15% better than G4. Unfortunately it's patented and not widely supported.