Technical Information

The digital images of the panoramas were produced by scanning intermediate 35 mm copy film at approximately 900 dpi. This translates into a digital image resolution ranging from approximately 50 to 100 dpi if one were attempting to reproduce the image at the same size as the original panorama. See The Digitization Process below, for further details.

The quality of a digital image reproduction cannot be pre-determined; users will need to experiment to see whether adequate results can be achieved for their specific purpose from these digital images. Factors that can affect reproduction quality include:

• desired size of reproduction (generally, the smaller the reproduction, the better it will appear)
• the device used to create the reproduction
• enhancing features that may be available in the digital imaging software used.

The Digitization Process

Initial Capture and Scanning (1992-1993)

The panoramic photographs have been digitized from 35mm film produced by a contractor in 1992-93 using a modified motion picture camera. The full-frame 35 mm exposures were made on color motion picture film stock. The contractor, Stokes Imaging, Inc., constructed a computer controlled table that moved the panorama under the camera, producing a sequence of exposures that represent overlapping segments of the original photograph. (Imagine a comic strip with overlaps.) The computer program tracked the number of segments and the amount of overlap to permit the "reassembly" of the panorama in digital postprocessing, where match lines were identified for each segment, the overlap cropped away, and the segments blended. The digital images were created at a resolution appropriate for video production, e.g., the individual segments were scanned at 560x480 pixels. In 1993, the resulting digital images (both the assembled whole views and all of the individual segments) were converted to analog video and copied to videodisc media.

Rescanning (1996)

In 1996, the 35mm copy film was rescanned for this digital presentation by another contractor, JJT, Inc., of Austin, Texas. Once again, the images for each segment were captured from the film in a computer controlled process that tracked the information needed for later assembly, with a base capture resolution of about 1000x700 pixels. Once again, the frames were assembled, this time to produce an archival or master digital image of the panoramic photograph. All other images used in the display (e.g., the thumbnail reference image) are derived from this master image. The master image is available for download as an "uncompressed archival tiff."

Minimal computer enhancements were applied to the archival image during the production process. In contrast, the enhancement called sharpening has been applied to the reference image and, as a result, it may look better in some display settings than the archival master.

The header of the master image indicates that the file carries a resolution of 900 dots per inch (dpi). This represents the approximate resolution of the scanning of the 35mm intermediate copy film. The resolution as related to the size of the original prints ranges from approximately 50 to 100 dpi. The dimensions of each original panorama can be found in the bibliographic record in the MEDIUM field.

Specifications

Initial segment capture

Spatial resolution:

about 1000x700 pixels

Tonal resolution:

color, 24 bits per pixel

Compression:

none

Enhancement:

none

Archival (master) image

Spatial resolution of short side (typically the vertical):

about 700 pixels

Spatial resolution of long side (typically the horizontal):

about 500 pixels times the number of original segments (approximate range: 1000-5000 pixels)

Tonal resolution:

color, 24 bits per pixel

Compression:

none

Enhancement:

none

Reference image

Spatial resolution of short side (typically the vertical):

420 pixels

Spatial resolution of long side (typically the horizontal):

approximate range: 700-3000 pixels

Tonal resolution:

color, 24 bits per pixel

Compression:

JPEG

Enhancement:

sharpening

Thumbnail image

Spatial resolution of short side (typically the vertical):

150 pixels or less

Spatial resolution of long side (typically the horizontal):

not to exceed about 600 pixels

Tonal resolution:

8 bits per pixel

Compression:

native to GIF

Enhancement:

color indexing, sharpening

Describing the Collection

Most of the Prints and Photographs Division's cataloging is considered "minimal level," because information is often limited to what is provided with the picture rather than what could be learned by fully researching the image. The following comments explain the general cataloging guidelines. They also point out which catalog record information is most useful for citing pictorial materials in research notes or publications. Since the original information accompanying a picture can be inaccurate, the Division is always glad to hear from researchers who have additional or better information.

The records for a single collection might not use each of the fields or have all of the indexing features described here. For general information about cataloging pictorial materials, see the Visual Materials: Processing & Cataloging Bibliography.

CALL NUMBER. This string of letters and numbers is used to locate the original material at the Library of Congress. The original work may be requested in order to see details not captured in digital reproduction or to create a new type of copy photograph. A code might display at the end of the call number to identify the custodial division, for example, [P&P] means the item is from the Prints and Photographs Division. Although P&P has a unique system of call number locations (and the patterns vary from filing series to filing series), the call number is still a useful reference citation.

CARD #. The control number, or card number, for each catalog record is a unique identification number. It can be used to do a quick number search when you want to see a specific record without repeating a long keyword or subject search. However, only some online catalogs provide an index by this number.

COLLECTION. The title of the collection associates each item with its source and is useful to include in bibliographic citations. Some items are in more than one collection, because they are associated with both a format-based collection (e.g., Daguerreotype Collection) and a donor-based collection (e.g., Frances Benjamin Johnston Collection). Other items lack a formal collection title heading because they are in collections that have not yet been fully cataloged. Such informal collection names often appear in the NOTES field.

CREATOR. When the name of the photographer, architect, printmaker, or other image creator is known, only one form of the name is used, so that it is possible to retrieve all works by one creator under a single spelling or form of the name. Birth and death dates are only included when such information is readily available. If the Library of Congress form of the name was established while the creator was still alive, a death date is not usually added when the creator dies. It is expensive to update such information, and the name is already uniquely identified in the catalog.

The absence of a creator's name indicates that the creator is anonymous, unidentified, or unknown.

After the name, a term appears to identify the relationship(s) between the name and the work being cataloged. For example, architect, copyright claimant, photographer, or publisher.

DATE. The date refers to the year(s) when the image being cataloged was created, not the time period depicted in the picture.

The date is transcribed when such information appears with the picture. It is difficult to assign a specific year to undated prints and photographs. The catalogers look for clues such as: styles of fashion shown in the image, photographer's life dates, or type of physical media. Often, only a span of years or decades can be estimated and such dates are shown in brackets, for example, [between 1900 and 1930].

When the single letter "c" appears before a date, it indicates the year in which an image was deposited for copyright.

The abbreviation "ca."means "circa" and indicates a date that is approximate within several years.

DIGITAL ID (or VIDEO FRAME ID). The identification number for the digital file begins with a word or phrase that explains the source used to create the digital image, for example, the "original" work or a "b&w copy film neg." The Library's digital images are often created by scanning one or more of the copy photographs listed in the Reproduction Number field.

FORMATS. The genre and physical characteristics of the original work are listed as plural index terms. Examples include: Broadsides, Engravings, Group portraits, Lithographs--Color, Paintings--Reproductions, Political posters, Portrait photographs, Stereographs, and Woodcuts.

These headings are sometimes subdivided by the nationality, place, or decade in which the work was created. Other subdivisions indicate if the work is in color or is a reproduction of another medium. The terms come from the Thesaurus for Graphic Materials II: Genre and Physical Characteristic Terms .

MEDIUM. The physical properties of the original work are described by listing a readily recognized broad category, such as photograph, drawing, or print, followed by a more specific designation, such as daguerreotype, charcoal, or aquatint. This is determined by examining the work. The description is also a reminder that the physical characteristics of the original work are quite different from a digital reproduction on a computer screen.

The quantity of material is also stated, although most records usually describe only a single item. Some records, however, describe tens or hundreds of items, and it is helpful to know the size of each work to understand the specificity of the information in the catalog record.

The dimensions of a work are rarely provided in minimal-level cataloging. Panoramic photographs, however, include dimensions, which are rounded off to the nearest half inch and measure the image area exclusive of borders and mounts.

NOTES. Many types of notes are written to explain reproduction restrictions, sources of devised dates and titles, the name of the collection to which the work belongs, citations to published versions, and other aspects of the work. A subject description is sometimes written if a title is not self-explanatory. With minimal-level cataloging some types of notes are omitted, for example, acquisition source is rarely provided.

OTHER TITLE: Additional titles by which the work is known.

RELATED NAMES. When multiple people or corporate bodies contribute to a work, their names can be listed as related, or added, entries. When the nature of the contribution can be specified, a relator term, such as client, copyright claimant, interior designer, or sculptor, is added after the name.

REPOSITORY. The name of the institution and division that have custody of the original work. This information can help you locate or cite the original.

REPRODUCTION NUMBER. This alpha-numeric code identifies existing black-and-white and color photographs from which prints, transparencies, and other photographic reproductions can be ordered. This number is also the most useful (and shortest) reference citation to include with any subsequent publication of the image.

A qualifying phrase identifies the type of reproduction (e.g., color transparency) and points out which reproductions are only details or cropped versions of the original works. This information can help you decide which of the copy photographs you want to reproduce.

The abbreviation "b&w" stands for black-and-white.

SUBJECTS. Catalogers assign index terms that describe what the image shows as well as what the image is about. For example, a political cartoon depicting a basketball game in which the players are dribbling a globe is "of" basketball and "about" international relations. Most of the topical terms come from the Thesaurus for Graphic Materials I: Subject Terms . The proper noun headings come from the Library of Congress Name Authority File and from the Library of Congress Subject Headings. Examples include: Baseball players; Document signings; Dogs; Flags--American; Ford's Theatre (Washington, D.C.); Log cabins; Pan-American Exposition (1901: Buffalo, N.Y.); Presidential inaugurations; Tippecanoe, Battle of, 1811; United States. Declaration of Independence; World War, 1939-1945.

Some collections have only preliminary index headings, and do not use standard vocabulary sources like the Thesaurus for Graphic Materials. For example, the Historic American Buildings Survey/Historic American Engineering Record uses an uncontrolled indexing vocabulary where different terms, such as "Car dealership" and "Auto dealership," are sometimes used for the same subject, because the material being cataloged used those different terms. The Gottscho-Schleisner Collection headings focus on terms for types of structures, for example, "Automobile dealerships" and use few proper names for subjects such as buildings. (The title includes an informal building or project name taken from the photographer's logbook.)

Terms are sometimes subdivided by place and date of depiction. In other cases, the place names are expressed as hierarchical geographic "strings" to allow keyword access to names of countries and states as well as counties and cities. For example, "Canada--British Columbia--Vancouver" or "United States--Maryland- -Baltimore."

TITLE. A title is transcribed from the original picture, or from a photographer's logbook or negative jacket. If the picture carries no caption a title is devised from another source and displayed in brackets. Devised titles are written by Library staff, or they might come from a published book illustration or a former owner.

The abbreviations "[sic]" and "[i.e.]" indicate erroneous spellings or information in transcribed titles. The correct information is provided as needed in the title or a note.