Film scanner
A film scanner is a device made for
Film scanners can accept either strips of
Some software used to process images scanned by film scanners allows for automatic color correction based on the film manufacturer and type. In many cases the source film may not be marked with this information in human-readable form, but might be marked at the bottom edge with a DX film edge barcode following a standard maintained by ANSI and I3A.
Dust and scratches
Dust and scratches on the film can be a big problem for scanning. Because of their reduced size (compared to prints), the scanners are capable of resolutions much higher than a regular flatbed scanner; typically at least 2000 samples per inch (spi), up to 4000 spi or more. At these resolutions dust and scratches take on gigantic proportions. Even small specks of dust, invisible to the naked eye, can obscure a cluster of several pixels. For this reason, techniques have been developed to remove their appearance from a scan, see
The simplest is the median filter, often called despeckle in many graphic manipulation programs, e.g. in Adobe Photoshop and the GIMP. It works by examining a pixel in relation to the pixels surrounding it; if it is too different from the surrounding pixels then it is replaced with one set to their median value. This and other methods can be quite effective but have the disadvantage that the filter cannot know what actually is dust or noise. It will also degrade fine detail in the scan.
Infrared cleaning
Infrared cleaning works by collecting an
Scanner manufacturers usually have their own name attached to this technique.
See also
External links
- A full array of image correction features for a variety of documents, Canon, archived from the original on 23 October 2010
- "Kodak Digital ICE", Products (overview), ASF.
- "iSRD", Highlights, SilverFast.