Фотосуреттерді сақтау және қалпына келтіру: физикалық күтім мен емдеу

Study of the physical care and treatment of photographic materials
The conservation and restoration of photographs is the study of the physical care and treatment of photographic materials. It covers both efforts undertaken by photograph conservators, librarians, archivists, and museum curators who manage photograph collections at a variety of cultural heritage institutions, as well as steps taken to preserve collections of personal and family photographs. It is an umbrella term that includes both preventative preservation activities such as environmental control and conservation techniques that involve treating individual items. Both preservation and conservation require an in depth understanding of how photographs are made, and the causes and prevention of deterioration. Conservator restorers use this knowledge to treat photographic materials, stabilizing them from further deterioration, and sometimes restoring them for aesthetic purposes. While conservation can improve the appearance of a photograph, image quality is not the primary purpose of conservation. Conservators will try to improve the visual appearance of a photograph as much as possible, while also ensuring its long term survival and adhering the profession's ethical standards. Photograph conservators also play a role in the field of connoisseurship. Their understanding of the physical object and its structure makes them uniquely suited to a technical examination of the photograph, which can reveal clues about how, when, and where it was made. Photograph preservation is distinguished from digital or optical restoration, which is concerned with creating and editing a digital copy of the original image rather than treating the original photographic material. Photograph preservation does not normally include moving image materials, which by their nature require a very different approach. Film preservation concerns itself with these materials.

Physical photographs usually consist of three components: the final image material (e. g. silver, platinum, dyes, or pigments), the transparent binder layer (e. g. albumen, collodion, or gelatin) in which the final image material is suspended, and the primary support (e. g. paper, glass, metal, or plastic). These components affect the susceptibility of photos to damage and the preservation and conservation methods required. Photograph preservation and conservation are also concerned with the negatives from which most old photographic prints are made. Most negatives are either glass plate or film based.

Photograph stability refers to the ability of prints and film to remain visibly unchanged over periods of time. Different photographic processes yield varying degrees of stability. In addition, different materials may have dark storage stability which differs from their stability in light. Kodachrome An extreme case with slides was stability under the intense light of projection. When stored in darkness, Kodachrome's long term stability under suitable conditions is superior to other types of color film. Images on Kodachrome slides over fifty years old retain accurate color and density. Kodachrome film stored in darkness is largely responsible for excellent color footage of World War II, for example. It has been calculated that the yellow dye in Kodachrome, the least stable, would suffer a 20% loss of dye in 185 years. This is because developed Kodachrome does not retain unused color couplers. However, Kodachrome's color stability under bright light, especially during projection, is inferior to substantive slide films. Kodachrome's fade time under projection is about one hour, compared to Fujichrome's two and a half hours. Thus, old Kodachrome slides should be exposed to light only when copying to another medium. Silver halide Black and white negatives and prints made by the silver halide process are stable so long as the photographic substrate is stable. Some papers may yellow with age, or the gelatin matrix may yellow and crack with age. If not developed properly, small amounts of silver halide remaining in the gelatin will darken when exposed to light. In some prints, the black silver oxide is reduced to metallic silver with time, and the image takes on a metallic sheen as the dark areas reflect light instead of absorbing it. Silver can also react with sulfur in the air and form silver sulfide. A correctly processed and stored silver print or negative probably has the greatest stability of any photographic medium, as attested by the wealth of surviving historical black and white photographs. Chromogenic Chromogenic dye color processes include Type "R" and process RA 4 (also known as "type C prints"), process C 41 color negatives. and process E 6 color reversal (Ektachrome) film. Chromogenic processes yield organic dyes that are less stable than silver, and can also leave unreacted dye couplers behind during developing. Both factors may lead to color changes over time. The three dyes, cyan, magenta, and yellow, which make up the print may fade at different rates, causing a color shift in the print. Modern chromogenic papers such as Kodak Endura have achieved excellent stability, however, and are rated for 100 years in home display. Dye destruction Dye destruction prints are the most archival color prints, at least among the wet chemical processes, and arguably among all processes. The most well known kind of dye destruction print is the Cibachrome, now known as Ilfochrome. Ink jet Some ink jet prints are now considered to have excellent stability, while others are not. Ink jet prints using dye pigment mixtures are now common in photography, and often claim stability on par with chromogenic prints. However, these claims are based on accelerated aging studies rather than historical experience, because the technology is still relatively young.

There are two main types of deterioration found in photographic materials. Chemical deterioration occurs when the chemicals in the photograph or negative undergo reactions (either through contact with outside catalysts, or because the chemicals are inherently unstable) that damage the material. Physical or structural deterioration occurs when chemical reactions are not involved, and include abrasion and tearing. Both types of deterioration are caused by three main factors: environmental storage conditions, inappropriate storage enclosures and repair attempts, and human use and handling. Chemical damage can also be caused by improper chemical processing. Too high relative humidity can cause fading, discoloration and silver mirroring, Sources of indoor pollution that affect photographs include paint fumes, plywood, cardboard, and cleaning supplies. Exposure to light causes embrittlement, fading, and yellowing. The damage is cumulative and usually irreversible. UV light (including from sunlight and fluorescent light) and visible light in the blue part of the spectrum are especially harmful to photographs, but all forms of light, including incandescent and tungsten, are damaging.

An example of digitization as part of a photograph preservation strategy is the photographic collection of the Tay Bridge disaster of 1879. These photographs have been digitized and disseminated more widely. Only the positive prints survive, owing to the widespread practice of recycling the original glass negatives to reclaim the silver content. Even when carefully preserved and kept in the dark, damage can occur through intermittent exposure to light, as shown by damage to the image of the intact bridge (at left). An example of a larger digitization project is the Cased Photographs Project, which provides access to digital images and detailed descriptions of daguerreotypes, ambrotypes, tintypes, and related photographs in the collections of the Bancroft Library and the California State Library.

Digital photo restoration is the practice of restoring the appearance of a digital copy of a physical photograph that has been damaged due to natural, man made or environmental causes, as well as age or negligence. Digital photo restoration utilizes image editing techniques to remove unwanted visible elements such as dirt, scratches, or signs of aging. People use raster graphic editors to restore digital images or to add or replace torn or missing portions of a physical photograph. Unwanted color tones are removed, and the contrast or sharpness of an image can be altered to restore the range of contrast or detail believed to be in the original physical image. Digital image processing techniques included in image enhancement and image restoration software are also used to restore digital photographs.

One of the first functions that neural networks began to successfully handle was the restoration of old photographs. Photo restoration algorithms using artificial intelligence work by analyzing existing flaws in old photos and then applying intelligent image processing techniques to correct and enhance them. These algorithms can automatically detect and fix common problems such as scratches, noise, discoloration, and background blurring.

Fragile or valuable originals are protected when they are replaced by digital surrogates, and severely damaged photographs that are physically impossible to repair are repaired by creating a digital copy. The creation of digital surrogates allows for the preservation of originals. However, the digitization process itself contributes to the deterioration of the object. It is considered important to ensure minimal damage to the original photograph due to environmental changes or careless handling. Preservation efforts have traditionally focused on physical photographs, but the preservation of digital surrogates of photography has become equally important.

Courts agree that, by its basic nature, digitization includes reproduction, an act reserved exclusively for copyright owners. Ownership of a work of art does not inherently entail a right of reproduction. Even without copyright permission, museums may copy and digitally restore images for preservation or informational purposes.

Photograph conservation involves the physical treatment of individual photographs. As defined by the American Institute for Conservation, treatment is "the deliberate alteration of the chemical and/or physical aspects of cultural property, aimed primarily at prolonging its existence. Treatment may consist of stabilization and/or restoration." Stabilization treatments aim to maintain photographs in their current condition, minimizing further deterioration, while restoration treatments aim to return photographs to their original state. Conservation treatments range from very simple tear repairs or flattening to more complex treatments such as stain removal. Treatments vary widely depending on the type of photograph and its intended use. Therefore, conservators must by knowledgeable regarding both of these issues. Guides for the preservation of personal and family photograph collections, such as Cornell University's Preserving Your Family Photographs and the AIC's Caring for Your Treasures, recommend that people contact a trained conservator if they have rapidly deteriorating negatives or photographs with active mold growth, staining from pressure sensitive tape, severe tears, adhesion to enclosures, and other types of damage requiring conservation treatment.

There are a number of international organizations concerned with conservation of photographs along with other subjects, including the International Council on Archives (ICA), the International Institute for Conservation of Historic and Artistic Works (IIC), and the International Council of Museums Committee for Conservation (ICOM CC). The Photographic Records Working Group is a specialty group within the ICOM CC. In the United States, the national membership organization of conservation professionals is the American Institute for Conservation of Historic and Artistic works (AIC) to which the Photographic Materials Group (PMG) belongs. The Northeast Document Conservation Center (NEDCC) and the Conservation Center for Art and Historic Artifacts (CCAHA) also play an important role in the field of conservation. The Image Permanence Institute (IPI) at Rochester Institute of Technology is one of the leaders in preservation research of images in particular.

Photograph conservators and preservation managers are guided in their work by codes of ethics and technical standards. The International Council on Archives publishes a Code of Ethics and Guidelines for Practice. Additionally, members of other professions (such as archivists and librarians) who deal with preservation of photographs do so in accordance with their professional organization's codes of ethics. For example, the Society of American Archivists Code of Ethics states that "Archivists protect all documentary materials for which they are responsible and guard them against defacement, physical damage, deterioration, and theft." The International Organization for Standardization (ISO) and American National Standards Institute (ANSI) both publish technical standards that govern the materials and procedures used in photograph preservation and conservation. The International Federation of Library Associations and Institutions has published a list of ANSI standards pertaining to the care and handling of photographs.