Why Do Benchmarking?
Because there are no standards for image quality and because different document types require different scanning processes, there is no "silver bullet" for conversion. This frustrates many librarians and archivists who are seeking a simple solution to a complex issue. I suppose if there really were the need for a silver bullet, I'd recommend that most source documents be scanned at a minimum of 600 dpi with 24-bit color, but that would result in tremendously large file sizes and a hefty conversion cost. You would also be left with the problems of transmitting and displaying those images.
We began benchmarking with conversion, but we are now applying this approach to the presentation of information on-screen. The number of variables that govern display are many, and it will come as no surprise that they preclude the establishment of a single best method for presenting digital images. But here, too,
the urge is strong to seek a single solution. If display requirements paralleled conversion requirements-that is, if a 600 dpi, 24-bit image had to be presented onscreen, then at best, with the highest resolution monitors commercially available, only documents whose physical dimensions did not exceed 2.7" ³ 2.13" could be displayed-and they could not be displayed at their native size. Now most of us are interested in converting and displaying items that are larger than postage stamps, so these "simple solutions" are for most purposes impractical, and compromises will have to be made.
The object of benchmarking is to make informed decisions about a range of choices and to understand in advance the consequences of such decisions. The benchmarking approach can be applied across the full continuum of the digitization chain, from conversion to storage to access to presentation. Our belief at Cornell is that benchmarking must be approached holistically, that it is essential to understand at the point of selection what the consequences will be for conversion and presentation. This is especially important as institutions consider inaugurating large-scale conversion projects. Toward this end, the advantages of benchmarking are several in number.
1. Benchmarking is first and foremost a management tool, designed to lead to informed decision making. It offers a starting point and a means for narrowing the range of choices to a manageable number. Although clearly benchmarking decisions must be judged through actual implementations, the time spent in experimentation can be reduced, the temptation to overstate or understate requirements may be avoided, and the initial assessment requires no specialized equipment or expenditure of funds. Benchmarking allows you to scale knowledgeably and to make decisions on a macro level rather than to determine those requirements through item-by-item review or by setting requirements for groups of materials that may be adequate for only a portion of them.
2. Benchmarking provides a means for interpreting vendor claims. If you have spent any time reading product literature, you may have become convinced, as I have, that the sole aim of any company is to sell its product. Technical information will be presented in the most favorable light, which is often incomplete and intended to discourage product comparisons. One film scanner, for instance, may be advertised as having a resolution of 7500 dpi; another may claim 400 dpi. In reality, these two scanners could provide the very same capabilities, but it may be difficult to determine that without additional information. You may end up spending considerable time on the phone, first getting past the marketing representatives and then closely questioning those with a technical understanding of the product's capabilities. If you have benchmarked your requirements, you will be able to focus the discussion on your particular needs.
3. Benchmarking can assist you in negotiating with vendors for services and products. I've spent many years advocating the use of 600 dpi bitonal scanning for printed text, and invariably when I begin a discussion with a representative of an imaging service bureau, he will try to talk me out of such a high resolution, claiming that I do not need it or that it will be exorbitantly expensive. I suspect the representative is motivated to make those claims in part because he believes them and in part because the company may not provide that service and the salesperson wants my business. If I had not benchmarked my resolution requirements, I might be persuaded by what this salesperson has to say.
4. Benchmarking can lead to careful management of resources. If you know up front what your requirements are likely to be and the consequences of those requirements, you can develop a budget that reflects the actual costs, identify prerequisites for meeting those needs, and, perhaps most important, avoid costly mistakes. Nothing will doom an imaging project more quickly than buying the wrong equipment or having to manage image files that are not supported by your institution's technical infrastructure.
5. Benchmarking can also allow you to predict what you can deliver under specific conditions. It is important to understand that an imaging project may break at the weakest link in the digitization chain. For instance, if your institution is considering scanning its map collection, you should be realistic about what ultimately can be delivered to the user's desktop. Benchmarking lets you predict how much of the image and what level of detail can be presented on-screen for various monitors. Even with the most expensive monitor available, presenting oversize material completely, with small detail intact, is impractical.
Having spent some time extolling the virtues of digital benchmarking, I'd like to turn next to describing this methodology as it applies to conversion and then to move to a discussion of on-screen presentation.