A

Architectural drawings

Graphic delineations made for the design and construction (or documentation of design and construction) of sites, structures, details, fixtures, furnishings, and decorations, as well as other objects designed by an architect or architectural office. Generally held by the Prints & Photographs Division; the most popular collections are the Historical American Buildings Survey (HABS), Historic American Engineering Record (HAER), and Historic American Landscaping Survey HALS).
Category: Images

Art prints

Commercially published, mechanically printed copies of individual paintings, prints, drawings, and other two-dimensional works of art.
Category: Images

Aspect ratio

The ratio of horizontal to vertical dimensions of an image (35mm slide frame is 3:2, TV 4:3, HDTV 16:19, 4x5 film 5:4).
Category: Images

B

Black and white

Consisting of shades of gray ranging from white to black; An image type lacking any chromatic data. Scans from black and white material (such as black and white negatives or microform) are scanned at 8-bit grayscale. Many times, for preservation purposes, black and white reproductions were made. No colorizing can be done.
Category: General

C

Color

In its usage for Duplication Services, it refers to the colors that appear on the material being duplicated (including, for instance, colored ink or yellowing of paper), prints made in color to show the color of the original, or a digital file scanned in the 24-bit color to show the color of the original.
Category: General

Compression

The reduction of data to reduce file size for storage. Compression can be "lossy" (such as JPEG) or "lossless" (such as TIFF LZW). Greater reduction is possible with lossy compression than with lossless schemes.
Category: Images

Contact print/Contact sheet

A photographic print that is identical in size to the negative from which it is made, generally showing multiple frames of film to help identify and choose images.
Category: Images

Contrast

A measure of the rate of change to the brightness in an image. High contract implies dark black and bright white content; Medium contrast implies a good spread from black to white; Low contrast implies a small spread of values from black to white.
Category: Images

Copy negatives

Negatives made from original material (such as photographs, prints, and negatives), generally for preservation purposes.
Category: Images

Copyright

A form of intellectual property law, protecting original works of authorship including literary, dramatic, musical, and artistic works, such as poetry, novels, movies, songs, computer software, and architecture. Copyright covers both published and unpublished works. Copyright does not protect facts, ideas, systems, or methods of operation, although it may protect the way these things are expressed. See Circular 1, Copyright Basics (PDF 1.1 MB).
Category: General

D

Daguerreotypes

Direct-image photographs on silver-coated copper; introduced in 1839 and in general use until ca. 1860; distinctive mirror-like surface; commonly in a case.
Category: Images

Digital high resolution TIFF

A digital image in uncompressed TIFF format. These high-quality images follow federal preservation standards.
Category: Images

Digital image

An image composed of pixels.
Category: Images

Digital PDF/Digital photocopy

A digital file in PDF format made from documents, books, and other paper material using a photocopy machine.
Category: Searcher

Digital prints

An image printed by professional photographers from a digital scan on to resin-coated photo paper.
Category: Images

Digitization

The process of converting analog information into digital format for use by a computer. Generally involves using a scanner or a digital camera.
Category: General

DPI (Dots Per Inch)

DPI stands for dots per inch, and was originally used specifically as a term in printing, providing a measure of how many dots of ink are placed on a print in distance of one inch. The terms DPI and PPI (pixels per inch) are used somewhat interchangeably today, with scanner manufacturers often providing specifications on resolution in DPI.
Category: General

E

8-bit color/grayscale

In 8-bit color, each pixel has eight bits assigned to it, providing 256 colors or shades of gray, as in a grayscale image.
Category: Images

G

General books

Books that are considered in the general collections of the Library of Congress.
Category: Searcher

Glass negatives

Negatives with a glass base, generally dry plate negatives or wet collodion negatives
Category: Images

Glossy

A photo paper surface which is smooth and shiny.
Category: Images

I

Illustrations

Images that explain or elaborate a written or spoken text; may be issued separately from the text. Published and unpublished illustrations are included, as are pictures made in one medium to be published as illustrations in a different medium.
Category: Images

L

Lantern slides

Hand-drawn, painted, or photographic images on glass, intended for viewing by projection; often made in sets. Photographic lantern slides were introduced in the United States by 1850 and popular through World War I; commonly 3.25 x 4 in. (9 x 10 cm.) with a black paper mask, a cover glass, and taped edges.
Category: Images

Legal Certification/Certification

The process of copying material and attesting to the copy being a true representation of the work. A letter of certification is signed and a seal affixed. The copies are bound along with the letter of certification.
Category: General

Legal Documents

Materials held by the Law Library. This includes legal records, international law, and legal commentary.
Category: Searcher

M

Manuscripts

Handwritten documents. This term is also used to describe material held by the Manuscript Division, which may include typed, printed, photographic, and three-dimensional items.
Category: Searcher

Maps

Graphic delineations at a set scale, of all or part of the earth or another celestial sphere indicating the relative position of selected artificial and natural features. Generally, Duplication Services uses the term "maps" to describe the holdings of the Geography and Maps Division. Maps are usually larger than a tabloid-size (11x17") sheet of paper and are usually considered oversize.
Category: Images

Master negative microfilm

A master negative reel of microfilm is created by filming the original. The Library of Congress would have a master negative if it was filmed by the Library of Congress.
Category: Microfilm

Matte

A photo paper surface which is dull.
Category: Images

Microfiche

A sheet of microfilm holding reduced images of material, such as newspapers, reports, maps, and manuscripts.
Category: Microfilm

Microfilm

Photographs of objects shown at greatly reduced size on a continuous reel of film, requiring magnification device or enlargement to view. Duplication Services provides reels of microfilm, paper enlargements from microfilm, and digitization of microfilm. Reels provided to patrons can only be positive reels, and Duplication Services can only create a positive reel if there is an existing negative reel in the Library of Congress collections. For other duplication methods (such as paper enlargements and digitization), reproductions can be made only from positive reels.
Category: Microfilm

Microfilming

The process to create the master negative microfilm reel from which positive reels of microfilm can be made. Microfilming is done when there is no existing reel of microfilm. Patrons must pay for the cost of microfilming (per exposure) plus for the printing of the positive reel that they will receive.
Category: Microfilm

Microform

The term to describe all forms of micrographic formats, including microfilm, microfiche, and aperture cards.
Category: Microfilm

N

Negative

An item displayed with opposite values from how it is meant to appear.
Category: Images

Negatives

Photographs in which the tonal values are the opposite of those in the subject to which the negative was exposed. Duplication Services uses the term negatives as a catch-all for the various types of transmissive light formats, including transparencies.
Category: Images

Newspapers

A type of periodical printed on newsprint.
Category: Searcher

Nitrate negatives

Negatives with a nitrocellulose film base. Manufactured from 1887 to 1950.
Category: Searcher

O

1-bit color

The lowest number of colors per pixel in which a graphics file can be stored. In 1-bit color, each pixel is either black or white.
Category: Images

Original

The material in the Library of Congress collections which is being copied. Used when describing the method of reproduction and the qualities of the reproduction. In this case, the "original" may refer to a copy that the Library of Congress has in its collection. The Library's item may not be the first version and may be a copy, but it is the original being converted to a new format.
Category: General

Original material

Items which do not have a preservation copy already made. This can include manuscripts, books, photographs, prints, and newspapers.
Category: General

Original negative

The negative which was initially created through photographic processes.
Category: Images

P

Periodicals

Serials usually issued at regular intervals and more frequently than annually.
Category: Searcher

Photocopy

A paper copy made of documents, books, and other paper material using a photocopy machine.
Category: Searcher

Photograph

General term for any photographic process of an image.
Category: Images

Photographic prints

Prints produced from negatives, by transfer photo processes, or, in the case of photograms, by the direct action of light on light-sensitive paper. Duplication Services cannot offer photographic prints, only digital prints.
Category: Images

Pixel

The smallest element of a digitized image. Also, one of the tiny points of light that make up a picture on a computer screen.
Category: Images

Positive

An item displayed as it is meant to appear, with correct light density, hue, and other light properties.
Category: Images

Posters

Single or multi-sheet notices made to attract attention to events, activities, causes, goods, or services; also, purely decorative posters. Posters are generally held in the Prints & Photographs Division and are many times oversize; however, for many posters, copy negatives and transparencies exist.
Category: Images

PPI (Pixels Per Inch)

PPI stands for pixels per inch, commonly used in describing the resolution of a digital image. The terms DPI (dots per inch) and PPI are used somewhat interchangeably today.
Category: Images

Printing negative microfilm

A negative reel of microfilm (typically duplicated from a master negative) from which a positive reel can be made. The Library of Congress only sells positive reels of microfilm.
Category: Microfilm

R

Rare books

Material housed in the Rare Book and Special Collections Division holdings. Includes early printed material, materials with an historical significance, and Medieval manuscripts.
Category: Searcher

Reflective light material

An object that is intended to be, or is generally, viewed or used in a manner in which some or all of the of light that strikes its surface is reflected. Examples include materials on paper such as books, maps, and photographs. The other type of material that Duplication Services can duplicate is transmissive light material.
Category: Images

Resolution

The number of pixels per unit length of an image. For example, pixels per inch, pixels per millimeter, or pixels wide.
Category: Images

S

Safety film negatives

Negatives that do not have a flammable film base; first introduced for still photography in the early 1900s.
Category: Images

Scanner

An optical device that converts images such as photographs into digital form so they can be stored and manipulated on computers.
Category: Images

Sheet music

Printed musical compositions.
Category: Searcher

T

Technical book

Technical books and reports are the scientific resources of the Library of Congress.
Category: General

Transmissive light material

An object that is intended to be, or is generally, viewed or used in a manner that allows light to pass through from one side of the object to the other. The viewing or use of the object is by way of the transmitted light. Examples of transmissive objects include photographic slides and negatives.
Category: Images

Transparencies

Sheets of transparent material, such as glass, thin paper, or plastic, bearing a photographic, printed, or hand-drawn image and designed to be viewed by light shining through them; often intended for use with a projection device.
Category: Images

24-bit color

In 24-bit color, each pixel has 24 bits assigned to it, representing 16.7 million colors. 8 bits--or one byte--is assigned to each of the red, green, and blue components of a pixel.
Category: Images