Images are scanned from a bound or unbound publication, chiefly from bound publications in the case of NATDP, however, because often they are the only copies and the publications are returned to the shelves. NATDP usually scans one record at a time, because its database tracking system tracks the document in that way and does not require further logical separating of the images. After performing optical character recognition, NATDP moves the images off the hard disk and maintains a volume sheet. Though the system tracks electronically, all the processing steps are also tracked manually with a log sheet. ZIDAR next illustrated the kinds of adjustments that one can make when scanning from paper and microfilm, for example, redoing images that need special handling, setting for dithering or gray scale, and adjusting for brightness or for the whole book at one time. NATDP is scanning at 300 dots per inch, a standard scanning resolution. Though adequate for capturing text that is all of a standard size, 300 dpi is unsuitable for any kind of photographic material or for very small text. Many scanners allow for different image formats, TIFF, of course, being a de facto standard. But if one intends to exchange images with other people, the ability to scan other image formats, even if they are less common, becomes highly desirable. CCITT Group 4 is the standard compression for normal black-and-white images, JPEG for gray scale or color. ZIDAR recommended 1) using the standard compressions, particularly if one attempts to make material available and to allow users to download images and reuse them from CD-ROMs; and 2) maintaining the ability to output an uncompressed image, because in image exchange uncompressed images are more likely to be able to cross platforms. ZIDAR emphasized the importance of de-skewing and filtering as requirements on NATDP's upgraded system. For instance, scanning bound books, particularly books published by the federal government whose pages are skewed, and trying to scan them straight if OCR is to be performed, is extremely time-consuming. The same holds for filtering of poor-quality or older materials. ZIDAR described image capture from microform, using as an example three reels from a sixty-seven-reel set of the papers and letters of George Washington Carver that had been produced by Tuskegee University. These resulted in approximately 3,500 images, which NATDP had had scanned by its service contractor, Science Applications International Corporation (SAIC). NATDP also created bibliographic records for access. (NATDP did not have such specialized equipment as a microfilm scanner. Unfortunately, the process of scanning from microfilm was not an unqualified success, ZIDAR reported: because microfilm frame sizes vary, occasionally some frames were missed, which without spending much time and money could not be recaptured.