Ahh yes the "magic" number of DPI.... Here's a few other considerations to add to the mix.
Resolution should also be tied to the details in the thing being scanned. For Microfilming documents, a quality scale was developed to ensure that items were captured at the proper level. The UIUC Library turned this method into a handy resolution calculator http://images.library.uiuc.edu/calculator/index.htm This was done some time ago and hasn't been updated to the current resolution best practices, so I'd be inclined to bump up the resolution a bit from what it reports as optimal. The important thing is that it doesn't focus on the size of the paper, but on the size of the smallest character or detail in what you are scanning. If your documents are pretty consistent, its easy enough to tell the scan operator what to use. But it also leaves room for upping the resolution when required - e.g. government publications that have 6pt font for footnotes, or maps and illustrations with fine details. We'd all like to follow the highest standards possible but sometimes reality means we can't do that. If corners must be cut, have a good, thoughtful and carefully considered reason for not following best practices. Instead of arbitrarily rounding down for everything, think about a triage system based on light sensitivity or fragility of the materials. Materials that are brittle or damaged should be scanned at higher resolution than materials that are in good condition and could take a re-scanning without further damage. Or you might identify certain collections as more important, or more frequently used to justify doing some materials at a higher resolution than other materials. Basing resolution on past requests is a sure way to paint yourself into a corner. Quality should be optimized for future use, not past use. Having a good estimate of what you're going to need can also help make the argument. TASI has a great storage calculator that can help with planning. http://tasi.ac.uk/resources/toolbox.html And lastly, resolution is only one metric for quality. Nothing wastes storage space faster than high resolution scans the use the wrong bit depth, have poor tonal quality or otherwise Richard rjurabn at uiuc.edu On Jan 8, 2008, at 10:24 AM, Perian Sully wrote: > Hi all: > > We're currently having a debate about the appropriate scanned image > sizes for archival documents. Our scanner doesn't scan into RAW, so > we're batting back and forth whether to save the master TIFFs as > 600 or > 300 dpi. > > On the 300 side: > 1) many of our archival materials were already scanned at 300 dpi > (that > being the original size I designated, but we've a long way to go yet) > 2) the majority of our reproduction requests are for 300 dpi JPG > 3) storage space concerns > 4) archive materials are mostly documents and don't necessarily > need 600 > dpi treatment > 5) since the documents aren't "precious" like the 3D materials and > photographs, we can go back and rescan if we really need a 600 dpi JPG > (ie. handling concerns aren't as great) > > On the 600 side: > 1) scan once and be done with it > 2) we do sometimes receive 600 dpi JPG requests > 3) storage is cheap > 4) make sure the master TIFF is as high as quality as possible, > since we > don't have RAW to fall back upon > > We're also thinking about scanning the documents at 300 dpi, and > photographs and 3D materials in 600. > > What do other institutions do? Any best practices we should fall back > upon here? > > Thanks in advance! > > Perian Sully > Collection Information and New Media Coordinator > Judah L. Magnes Museum > 2911 Russell St. > Berkeley, CA 94705 > 510-549-6950 x 335 > http://www.magnes.org > Contributor, http://www.musematic.org > > _______________________________________________ > You are currently subscribed to mcn-l, the listserv of the Museum > Computer Network (http://www.mcn.edu) > > To post to this list, send messages to: mcn-l at mcn.edu > > To unsubscribe or change mcn-l delivery options visit: > http://toronto.mediatrope.com/mailman/listinfo/mcn-l
