Some scanners require regular calibration. How often depends on the specific scanner and what it has been scanning. Most of the original manufacturer software does not have a calibration option (however, Creo and Contex (and potentially others) scanners are an exception). SilverFast software is being used by one state geological survey to calibrate their Epson and Nikon scanners that allows for IT8 color calibration using a special IT8 color target (reflective and transparent available, for more information, please see Scanning Hardware). Older scanners with florescent tube lighting are less stable than newer LED lighting. The florescent tubes can take some time to warm up and have a consistent light intensity (10-15 min sometimes), and the intensity diminishes over time as the tubes age. That is not an issue with LED lighting.
It is helpful to have scanners connected to a power conditioner that provides a constant AC voltage to the scanner (120 VAC), even if the input voltage varies. This can be an issue in buildings where large electrical loads cycle on and off (this is very common). Much better uninterruptible power supplies (UPS), such as from APC and Tripp-Lite, also do power conditioning and filtering (reduces line noise), and tend to make equipment last longer. Low AC input voltage is very damaging to electronics.
It is helpful to inspect the glass surface, some scratch easier than others. They should be cleaned with camera lens quality cloths and solution. If scratches from the scanner glass are present in the resulting image, the glass should be replaced. Presently, few manufacturers are still producing scanners, for all but very specialized uses.
One state geological survey uses the Epson Expression 12000XL model, which is a tabloid-size scanner with transparency capability, and the V850 model is used for photo/negative scanning.
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