A photographic index serves many functions, but most importantly it can, "maintain control over a repository's holdings as well as to inform researchers" (Orbach 1990, 168). The index serves as an inventory of a defined sub-set of the collection, in this case Civil War images. It provides staff a tool to quickly assess the "size and scope of its holdings" (Orbach 1990, 168). In the acquisitions area, an index can provide the necessary information to target areas of need, or to avoid duplication of currently-held materials.

An index can also prove invaluable should the need arise to produce documentation for damaged or missing items. Many archives have been publically embarrassed when the need to provide descriptions of holdings has proven difficult or impossible to accomplish. As one author (Samuel 1988) sadly relates, "many museums have initiated documentation projects only after the loss of an important object with concomitant embarrassing publicity".

For the researcher, staff or public, the benefits of an electronic index are self-evident. At its most basic level, it must provide both intellectual and physical access to all items in a given collection. Access is the primary concern of archives because, "photographs are only worth preserving in an archives if they will eventually be utilized by researchers" (Tolppanen, 1996, 12). The ability to perform a comprehensive search of a collection from a single-source index is a critical element towards providing item-level access.

One institutional advantage to providing a graphic index is collection preservation. Whether the surrogates are text-only, or text combined with images, a distinct benefit is the decreased handling of the original images. Fingers are "more destructive than any chemical or moisture phenomena" (Schwalberg, 1982, 85), so any procedure that limits handling of photographs is a sound preservation practice.

The objectives of an image index should be identical to the principles already established for subject control of all items, both textual and graphic. Charles Cutter (1904) defined these objectives as:

1. To enable a person to find a book of which...the subject is known
2. To show what the library has...on a given subject
3. Bringing books together which treat of the same subject specifically, and which treat of similar subjects

Thus, the goals of cataloging serve two quite different functions: to isolate a specific item, but also to group items by similar or related subjects. Current cataloging practices accomplish these seemingly antithetical goals through a combination of descriptive and subject cataloging. Generally speaking, the descriptive portions of a bibliographic record help to identify a specific item, while the subject portions help to group and combine items by subject. While the goals of an image index should not differ from Cutter's principles, the construction of its bibliographic records should be idiomatic for both graphic images and the specific collection being indexed.

The cataloging of photographs presents several special challenges inherent to images. In the area of descriptive cataloging, photographs are often not self-identifying. Unlike textual works that provide such essential cataloging aids as title pages, abstracts, and tables of contents, photographs often contain no indication of author/photographer, names of persons or places depicted, dates, or any textual information whatever. As a result, the cataloger may be forced to research the item, or to interpolate details by considering the item in relation to the balance of its accession group, its "Respect de Fond". This archival concept states that, "...a group of records in an accession...should be kept together regardless of the formats involved or the nature of the records" (Tolppanen, 1997). Thus, the cataloger is aware of the content of the accession as a whole, and is free to draw conclusions drawn from the intellectual sum of its parts.

In the area of subject cataloging, the cataloger is challenged by the subjective nature of the intellectual elements of graphic collections. It is well-documented that little agreement exists between users or leven ibrary professionals in the choice subject terms for images (Collantes, 1995). Consequently, prediction of researcher/cataloger subject term selection is very difficult. It is axiomatic that the subject terms entered into the database/index by the cataloger must match the terms selected by the researcher. This match is the most critical method of evaluating the performance of an index. "An inconsistent, or otherwise poorly done effort will result in a confused retrieval system and a grossly underused photograph collection" (Tolppanen, 1996, 28).

The first step in any graphic index is the challenge of translating, condensing, and organizing visual information into written language (Tolppanen, 1996). Whether the index contains visual surrogates or not, the initial step for both cataloger and researcher alike is to represent visual concepts in textual form. Given that the two forms contain different types of information, this step presents a challenge to both parties.

Objective intellectual control has its own set of factors. An image's aesthetic and/or emotional appeal can affect the appraisal of the archival or intellectual qualities of a photograph (Greenberg, 1993). Graphic materials perceived as having informational value, were originally created for different purposes, known as their evidential value. Potential informational uses of these materials are as varied as the researchers that will use the index, and it is nearly impossible to anticipate, "all the reference questions that a given image might satisfy" (Benemann, 1994, 45).

Probably the most challenging question concerns the level of description, or specificity, assigned to an item. Three levels of description have been identified, ranging from concrete to symbolic (Panovsky, 1983). The first level, the primary level, describes specifically the physical objects within the image. It reveals what the picture contains, its "ofness". This level best satisfies information requests that are of an objective or factual nature, such as searches for individual persons, places, events or objects. The secondary level is concerned with interpreting the objects within the image in a cultural context, and can be summarized as representing what the image is "about". This level is more subjective, and, "is based on knowledge acquired from familiarity with the customs and cultural traditions of a particular civilization" (Leung, 1992, 112). Traditionally, this level has been used to catalog images in the field of art history, and requires that both the indexer and researcher have expert knowledge of the field. However, this level, when coupled with the primary level, can satisfy many types of requests because, "pictures are simultaneously generic and specific" (Shatford, 1986, 47). For example, an image specifically "of" Sergeant Adam Horine (110th O.V.I.), is also generically "about" an Ohio Civil War soldier, a Union Soldier, an example of a tin-type image, the uniform of a Union Sergeant in the Army of the Potomac in 1864, and a soldier with a battle-hardened visage, to name but a few. Panofsky's third level of deception, the iconological, is concerned with deep intrinsic or symbolic meaning, and, "cannot be indexed with any degree of consistency" (Hahn, 1994, 3), and is seldom included in indexes.

As previously stated, an index must provide both physical and intellectual control of the collection. The former includes the steps of acquisition, accession, and processing of each collection. In order to establish physical control on an item-level, each image must be assigned a unique catalog number. This number is the necessary first step for creating an indexing, storage, and retrieval system, and should be written on the back of the item with a only soft granite pencil.

Once this physical control has been established, the intellectual control process can begin. The indexer must choose access points and vocabulary that are most likely to match the needs and skill level of its researchers. This is a critical and difficult task, and the solution is unique to each institution and each collection. The most appropriate method of prediction is that of charting past information requests within the institution.

An important facet for intellectual control of an image index is the choice of a controlled vocabulary for subject terms. The Library of Congress Subject Headings (LCSH) has traditionally offered intellectual control over archival material, albeit mostly of "textual, book-length materials" (Greenberg 1993, 89). But as the sophistication of image databases has grown, the limitations of LSCH as a subject list of visual materials have become apparent, and as one author (Greenberg, 1993) observes, "LCSH does not always provide terminology for the specific concepts that are represented in visual archives". As a result, two thesauri have subsequently been designed specifically for graphic materials: the Art and Architecture Thesaurus (AAT), and the Library of Congress Thesaurus for Graphic Materials (LCTGM).

The stated goal of the ATT is to construct an extensive controlled vocabulary for the disciplines of art and architecture, which is structured to meet the needs of the scholars and researchers in each field (Greenberg, 1993). This highly specialized source uses terminology that is familiar to a relatively specialized audience, and deals largely with Panovsky's second level of description, the culturally-based "aboutness" of an image. This level of description generally excludes access to factual images elements, and also tends to exclude novice or casual users (Leung, 1992).

The LCTGM appears to be a much more appropriate choice of thesaurus for the OHS collection. It grew from the recognition of the limited nature of LCSH to satisfy the subject needs of pictorial materials. The stated goal of LCTGM is simply to, "promote standardization in image cataloging" (LCTGM, 1995, 13). This thesaurus was authored by The Library of Congress Prints and Photographs Division, and is structured towards a more general image collection than is the AAT. The major advantage of LCTGM for this institution is its ability to provide, "subject indexing to visual materials founds in libraries, historical societies, archives, and museums" (Greenberg, 1993, 95). The LCTGM is designed to provide guidance for both indexer and researcher, and is a pragmatic tool to facilitate subject term matching between the two. LCTGM is fully available online, suggesting that a searchable Web index created from it, should also contain a hyper-link to it to, as a reference aid to researchers. The fact that the Library of Congress has an extensive Civil War photograph collection that has helped shape this work, makes LCTGM a highly appropriate model for the OHS collection. It will supply subject heads for most items in the collection, and has the added benefit of being familiar to some experienced researchers that may have previous experience searching the Library of Congress indexes for similar items. Both the AAT and the LCTGM are based on LCSH, and most reports indicate that all three sources are necessary in the processing of large image collections.

Another choice to consider is that of the level of indexing to provide. Archival collections can be represented at the collection, box, folder, or item-levels. There exists is no clear-cut school of thought as to which level is most beneficial for each separate collection. This decision is collection- and institution-specific, and must be made by the collection-processor. Generally, the highest level of detail should be provided for the collections that are the most requested. Also, the larger the collection, the greater the need for item-level control. Some advocate that all images collections, unlike textual records, must be controlled at the item level (Huyda, 1977). Many factors play into this decision, among them the, "size of the collection, historical importance, access restrictions, and potential research uses, as well as the financial support and staff time which is available" (Tolppanen, 1996, 23). The higher the level of detail, the more expensive the project, but these considerations must be weighed against future collection use and research time saved.

To provide item-level access to the cumulative body of Civil War photographs, rather than just the ready-reference collection, can literally pay-off financially. One recent research study (Tolppanen, 1996) concludes that,

The substantial financial resources produced by photographs, the biggest money earner in the archives, can be used to improve the quality of the institution. Several institutions reported that the substantial profit obtained through the sale of photographs was sufficient for the institution to fund their conservation program or purchase such new items as microfilm readers.