Jonathan Ingram wrote:

Obviously 600DPI full colour looks better than 300DPI bitonal, but this extra quality comes at a high price. Personally, moving from one to the other would not happen until someone buys me a faster scanner, a faster computer, a new large hard disk, and pays me for the extra time it will take me to scan and process the material even with this upgraded equipment. Even then, the high quality scans will never get off my computer unless you buy me a faster internet connection.

Even if some people do decide to make high resolution masters, there's little need to make colour scans of black-and-white originals. Grayscale, maybe, but all a colour scan will show you is how yellowed the paper is.

You also blithely say 'backup the original master scans', perhaps ignoring just how large lossless full-colour 600DPI scans are. Because I've been scanning for OCR, I can store the over 900 items I've scanned for DP on my hard disk (the folder takes up a little over 33 GB). A single large and long book scanned at 600DPI full-colour could end up taking up that much space by itself... and I don't particularly want to have to burn multiple DVDs every single time I scan something (ah yes, you'll need to pay for the DVD recorder and media).

I know how large those scans are. :^( Another acceptable solution is not to permanently save the first generation raw scans, but to preserve the second generation cleaned up versions which have been deskewed (using the right algorithm!), cropped, and for black and white source converted to greyscale (but kept at 600 dpi.) One reason for full-color scanning of even black and white source material is that due to the color characteristics of the background paper, some color channels may be cleaner (essentially "whiter") and could be used for conversion to greyscale. I learned this trick from the DP forum. </smile> In the "My Antonia" scan project (the source of which is entirely black and white), the entire scanset of deskewed, cropped, and still full color scans at 600 dpi (all 430 pages plus separate illustration scans) amounts to 5.8 gigs (losslessly compressed as PNG, which achieved about a 50% compression.) If I were to convert them to grey scale, which now seems like a good idea once I determine the best color channel to use, the whole file set should reduce down to 1.9 gigs as PNG -- I think one could fit 2 or 3 projects like this on a single DVD-ROM. I also have a derived scan set of 600 dpi bitonal -- that amounts to a paltry 49 Mbytes -- now 10 or 12 of these could fit on a CD-ROM. Similarly, for the "Kama Sutra" project, with 190 pages or so, the deskewed, cropped, 600 dpi greyscale PNGs total to 660 Mbytes, almost fittable on a CD-ROM. So, yes, your point is well-taken about the real raw full color 600 dpi scans that come off the scanner. I think it is acceptable, for archiving, to chuck these once the deskewed (again using the right algorithm), cropped, 600 dpi greyscale versions (generated from the best color channel) are generated. So I revise somewhat my suggestion. Jon