ISSN 1918-8153
Preservation of Photographic Materials
Tomasz Neugebauer
December 2005
1. Table of Contents
2. Introduction
3. Storage Conditions
4. Handling and Fluctuation in RH
and Temperature
5. Silver
Photographic Prints
6. Negatives
7. Copying and
Digitization
8. Conclusion
9.
Works Cited
Ideal preservation environments required for photographic materials are not comfortable for human researchers. This raises the question of a trade-off between access and preservation that has traditionally met with considerable skepticism from the archivists who are naturally concerned with the long-term survival of the materials. Joanna Sassoon argues that
“While digitizing can be justified on the grounds of preserving the original by reducing handling while facilitating access to the image content, any short term investment afforded in pursuit of the current trend towards commercialisation of photograph collections should not be at the expense of long term preservation of the provenance of the collection or the physical object from which the digital source originates.” (Sassoon 1998: 13)
It is because I essentially agree with the above statement by Sassoon that I combine in this paper a review of preservation techniques for physical photographic materials such as negatives and various types of prints with a review of copying and digitization strategies. The implicit point of view is that of an advocate for approaching digitization of photographs as an extension of expertise in preservation and access as opposed to an entirely new paradigm.
Susie Clark outlines the importance of improving handling, procedures and providing suitable storage conditions for photographic material. Proper handling and storage effects large numbers of photographs and it is cheaper than restoration through chemical treatment. Chemical treatment and restoration is necessary for some prints, but, “there is no point in repairing a photograph only to replace it in poor surroundings” (Clark 1990: 41). Alice Swan (1981) points to a precondition for proper preservation of photographs: accurate appraisal of the collection. Photographic materials can be undervalued as a class of research materials due to the “negative-positive generation system [that] implies replaceability” (Swan 1981: 270). As Donald E. Ross says, “we have billions of photos and we treat them that way.” (Ross 1996: 8) It is easy to overestimate the extent to which actual archival quality negatives that have been properly stored are available as well as the extent to which replacement prints will be identical to the originals. (Swan 1981: 270)
The development of a preservation plan for photographic collections requires answers to questions of quantity and quality of the collection. The relevant quantities include numbers of negatives and prints of each form (glass, nitrate, acetate, polyester, black & white, colour) whereas the qualitative analysis should result in a selection of specific groups within the collection: which materials are deteriorating?, which are most important to collection and researchers? (Wilson 1998: 4)
The Canadian Council of Archives (CCA) basic guide to preservation offers general chapters for mixed and paper collections as well as various specific forms of photographic materials (C.C.A. 1990). The problems of foxing (yellow-brown aging stains) and mould growth are common to other paper items, but adhesion of gelatin layers and glass rot (at high humidity) and flaking emulsions (low humidity) are unique to photographic materials (Clark 1990: 41). Photographs consist of multiple layers, each of which reacts differently to humidity levels. Gelatin papers, for example, consist of these 4 layers: paper base, gelatin-barium sulfate, light-sensitive ‘emulsion’ containing the image, and a protective gelatin (Swan 1981: 280).
Photographic materials encode the image by reacting chemically with their environment and although this reaction is ‘fixed’ in the process, it is essential to understand that the materials continue to be sensitive to light and chemistry in their environment. Relative humidity (RH) is identified by Clark as “the most important environmental factor” (1990: 41): it should be 35-40% for a “mixed photographic collections” (Clark 1990: 41). Alice Swan similarly recommends RH control of about 40% in order to prevent fading of image silver (1981: 285) and ferreotyping (adhesion of mylar to print surface) in gelatin prints (1981: 284) as well as minimizing oxidation of silver (1981: 287). The visible signs of oxidization follow this order: shift in hue of the image highlights to yellow, spot formation in the midtones, shadow areas move towards red, and uniform fading (Swan 1981: 286).
The American National Standards Institute (ANSI) recommends 20° C and 30-40 percent relative humidity (RH) as base line environmental conditions (Wilson Part 1 1998: 4). Susie Clark recommends ideal temperatures of 5-8˚C for mixed photographic collections (up to 10-15˚C is acceptable) and 2˚C for colour film (Clark 1990). Swan warns against temperatures in excess of 22˚C to prevent oxidation (1981: 287). McCormick-Goodhart concludes that the optimum way to preserve photographic materials is to provide separate environments for storage and exhibition and to control the amount of time spent in each (1996: 19). He finds the optimum storage conditions to be those that increase chemical stability: sub-zero temperatures of -20˚C to -25˚C. (McCormick-Goodhart 1996: 19)
Susie Clark lists the air pollutants that are responsible for ‘silver mirroring or tarnish’ that can lead to the complete destruction on an image: acids, peroxides, ozone, sulphur-containing compounds and nitrogen oxide (Clark 1990: 42). The mirroring effect is the result of the transformation of image silver to silver sulfide, described by Alice Swan as “the natural end product of a variety of image deterioration processes” (1981: 288). Oxidation is a contributing factor to mirroring. In addition to controlling sources of active sulphur (e.g.: sulphur dioxide) through air-conditioning, storage materials without peroxide or active sulfur sources must be used. (Swan 1981: 288) Archival storage materials should be tested for these active pollutants because they are not commonly controlled in all ‘archival’ materials like pH levels. Therefore, all paper and board materials for negatives and prints must pass a Photo Activity Test (PAT) [*] to be truly archival photo storage material (Wilson Part 2 1998: 4).
Handling and Fluctuation in RH and Temperature
Handling of photographs should always be done in a clean environment, using cotton gloves and kept away from tape, glue, rubber-bands, thumb-tacks or paper clips. Original photographs should not be exposed to direct sunlight or fluorescent light without filters since the ultraviolet (UV) range causes fading and discoloration, especially in colour prints. (Zanish-Belcher 1997: 5; Wilson Part 1 1998: 4) Copy photographs are always preferable to an original for permanent or long-term display (Wilson Part 1 1998: 4). Canadian Council of Archives recommends total darkness for photographic prints whenever possible, 50 lux [†] for exhibition of original prints and 100 lux or higher for copies (C.C.A. 1990: 77).
Susie Clark recommends that RH should not fluctuate more than 5% since this would cause the layers of photographs to separate (1990: 41). Although the physical damage resulting from fluctuating RH and temperature has been difficult to quantify, damage in the form of cracks, flaking, warping and curl results from exposure to fluctuations outside of an allowable range (McCormick-Goodhart 1996: 8). Although modern HVAC systems can control temperature within ±1˚C and ±2% RH, such narrow tolerances raise the issue of ‘frequency of access versus the physical well-being of the collection’ (McCormick-Goodhart 1996: 8). In order to maximize access while ensuring physical well being, McCormick-Goodhart carries out research to measure exact ‘yield points’ of materials (gelatin prints) at which they still contract due to these fluctuations “in a completely reversible manner.” (1996: 8)
Mylar sleeves should be avoided if the access environments include humidity levels above 65 %, since the sleeves trap excessive moisture and invite mold on gelatin and albumen prints (Swan 1981: 285). Materials have to be warmed slowly to avoid condensation and handled carefully since they are inelastic and brittle when cold. The safe limits on access environments are between 35% - 65% humidity at 25˚C. (McCormick-Goodhart 1996: 19) Temperature and humidity must be adjusted simultaneously (reducing RH by 3-4% for 10˚C drop) “to compensate for the moisture absorption capacity of the gelatin” (McCormick-Goodhart 1996: 19). Alternatively, cold storage should not be used for items that are accessed frequently, due to possibility for formation of condensation (Clark 1990: 41).
[†] the International System of Units unit of illuminance (luminous flux per unit area). It is equal to equal to one lumen per square metre (1 lx = 1 lm/m2), moonlight represents about 1 lx. (<http://en.wikipedia.org/wiki/Lux> visited 20 Nov. 2005 )
Photographic materials have evolved since Louis Jacques Mandé Daguerre’s process[‡] of fixing images of the camera obscura was initially presented to a joint gathering of the Académie des Sciences and the Académie des Beaux-Arts in Paris, 1839 (Schwartz 2000: 4). The original daguerreotype (1840-1855) was a unique image on a plate of polished silver on copper, placed in a case and covered with a brass mat and glass. Ambrotypes (1855-1860; silver images on glass, bound by a collodion coating) and tintypes (1856-1920s; silver image on lacquered iron bound by collodion) were usually stored in similar cases. These early images should not be touched directly and be stored flat in acid and lignin free containers (Zanish-Belcher 1997: 1). These case photographs “are believed to be stable to light” with their protective cases (C.C.A 1990: 77).
Examples of daguerreotypes, ambrotypes and tintypes from the Library of Congress:
Different care is necessary for prints, depending on their underlying physical structure and processes used to fix the image. The image of a photographic silver print “consists of finely divided silver metal contained in or on an organic colloid layer (albumen, collodion, gelatin, or starch), present as a discrete coating or as sizing, on a paper support” (Swan 1981: 271). The CCA guide recommends individual enclosures for each photograph as protection against dust, dirt, handling and the environment (C.C.A. 1990: 79). The CCA guide also recommends lignin-free and unbuffered paper storage such as envelopes or folders and inert uncoated polyester (mylar) storage such as sleeves, encapsulation, or sheet holders (C.C.A. 1990: 80).
Among the earliest photographs (1840s - 1860s) are salt prints: paper “treated with solution of sodium chloride, dried, and treated with silver nitrate solution, forming silver chloride in and on the surface of the paper.” (Swan 1981: 272) These prints are unique in that the silver particles are directly on the paper. Common signs of deterioration of these prints include faded edges, yellowing, and surface deposits (i.e. dirt). Caring for these prints includes avoiding exposure to unnecessary light, providing low-humidity storage and surface protection in the form of mylar interleaving sheets for matted prints (placed between the mat and the print) and mylar sleeves with rigid supports for unmatted prints (Swan 1981: 273).
Example of salt print from the Library of Congress, Prints and Photographs Division:
The artist's van; Marcus Sparling, full-length portrait,
seated on Roger Fenton's photographic van; photographic print [1855]: salted paper ; 17.5 x 16.5 cm; Fenton,
Roger, 1819-1869, photographer;[LC-USZC4-9240
(color film copy transparency) LC-USZ62-2319 (b&w film copy neg.)]
<http://hdl.loc.gov/loc.pnp/cph.3g09240>
Salted paper prints 1850-1860.
The discovery and embrace of photography in these initial years revolved around science and travel. Daguerre’s camera obscura was in the process of becoming an indispensable “means of extending the powers of human observation” (Schwartz 2000: 5). Photographs were considered a breakthrough in their reliability and evidential authenticity as direct and detailed exact copies of objects from nature allowing for a new way of knowing and representing the world across space and time for explorers and scientists as well as “a surrogate for travel” (Schwartz 2000: 13). It is ironic that today’s digital imaging technology is often imbued with similar enthusiasm for its ability to skip through the physical materiality of the image altogether and remain entirely in the virtual realm.
In addition to salt prints, there are early (1850s – 1920s) albumen (sodium chloride solution with egg whites) prints such as those of Muybridge, Watkins, Jackson and O’Sullivan (Swan 1981: 273). Signs of deterioration of these prints include curling, the formation of a network of fissures (unevenly shaped segments) on the albumen, cleavages between these segments through which underlying paper is visible, and segment cupping (albumen pulls up at edges) (Swan 1981: 274). Water treatments increase the cleavages as the print dries which rules out wet mounting and leaves the use of mylar interleaving sheets tacked over the print to restrain curling (Swan 1981: 278). In order to avoid the ‘pinch’ and creases resulting from handling of these prints, Swan recommends secure attachment to rigid supports (Swan 1981: 279). Salt and albumen prints as well as early RC papers are particularly susceptible to fading and should be kept in darkness as much as possible (C.C.A. 1990: 78).
Examples of albumen prints from Library of Congress, Prints and Photographs Division:
Salt Lake City, Utah. by Jackson, William Henry,
1843-1942, photographer; photographic print
mounted on mat board : albumen ; image 42.8 x 53.5 cm; [LC-USZ62-119588 (b&w film copy
neg.)] <http://hdl.loc.gov/loc.pnp/det.4a32595>
Albumen prints.
The Horse in motion.
"Sallie Gardner," owned by Leland Stanford; running at a 1:40 gait
over the Palo Alto track, 19th June 1878 / Muybridge, Eadweard; c1878; print on card : albumen; [LC-USZ62-45683 (b&w film copy
neg. of copy 2)] <http://hdl.loc.gov/loc.pnp/cph.3a45870>
Mirror Lake, Yosemite by Watkins, Carleton E., 1829-1916; albumen print; [San Francisco :
Carleton E. Watkins,
ca. 1879]. [LC-DIG-stereo-1s01356
(digital file from original photo, front)]
<http://hdl.loc.gov/loc.pnp/stereo.1s01356>
Collodion (cellulose nitrate) prints were also made in this early period between 1890s-1910s. They are recognizable by their ‘plastic’ glossy feel that is impermeable to water and showing no fissures (Swan 1981: 279). Preservation of these prints calls for rigid supports (museum board) and surface protection (mylar mats) against abrasion and dirt (Swan 1981: 279).
Example of collodion print from Library of Congress, Prints and Photographs Division:
[Panoramic view of
Spearfish, S.D.]; collodion
printing-out paper ; 7
x 34.5 in.; c1902. [pan 6a09776]
<http://hdl.loc.gov/loc.pnp/pan.6a09776>
Since the 1870s, the dominant printing has been done on multi-layer gelatin prints. These can be differentiated from albumen prints through lack of fissuring and from collodion prints by their permeability to water (Swan 1981: 280). Relative humidity control is crucial to prevent curling, warping and deforming caused by the different rates of expansion and contraction of the layers [§] (Swan 1981: 281). Mylar sleeves and interleaving can cause contact spots on gelatin prints so packaging modifications need to be introduced to lift the mylar window away from the print surface (Swan 1981: 284). Furthermore, residual thiosulfate from the fixing process is a particularly acute problem for gelatin prints due to the retentiveness of the gelatin, causing fading and yellowing with time (Swan 1981: 289). ‘Careful rewashing procedures’ can correct this problem (Swan 1981: 290).
Example of gelatin print from Library of Congress, Prints and Photographs Division:
Seventy-one years, or, My life with photography. Study of sunlight and shadow by Gottscho, Samuel Herman; photographed 1916, printed later; silver gelatin print. [LC-USZC2-4154] <http://hdl.loc.gov/loc.pnp/gsc.5a00047>
Colour prints (and negatives) introduce the new difficulty of dyes which fade more quickly over time than black & white. All photographs are a result of chemical reaction with light so it is obvious that a lifespan of a photograph can be measured in exposure to light. As a result, photographs should not be placed on display for more than a year even in dimmed (50 lux) light (Wilson Part 1 1998: 5).
Dry mounting using heat-set adhesives was a popular archival preservation method in the 1960s that should be avoided on original prints because it causes splitting of layers in gelatin prints, severe fissuring and cleavages in albumen layers and darkening and scorching of salt prints (Swan 1981: 283). The CCA guide warns against trying to remove photographs from mounting boards in favour of mylar encapsulation ‘as is’ with additional board support, as well as against trying to unroll photographs without a professional conservator (C.C.A. 1990: 80). Steel shelves, cabinets and drawers are preferable to wooden storage for chemical reasons (C.C.A. 1990: 80).
[‡] the process was based on the work of Joseph Niéphore Niépce who used a camera obscura to fix an image on stone in 1824. (Zanish-Belcher)
[§] emulsion and binder expand the most and the paper base the least (Swan 1981)
Glass negatives should be stored vertically (Clark 1990: 42), in four-flap negative enclosures to prevent peeling emulsions, and PAT-tested boxes to be labeled as heavy to prevent accidents (Wilson Part 1 1998: 4). Glass negatives can crack or break, but are otherwise well supported by the underlying material, which is not the case with the flexible film (Wilson Part 1 1998: 3).
Eastman Kodak first pioneered flexible, transparent film in 1889. Built on cellulose-nitrate, this film had a strong tendency to curl and was extremely flammable[**]. Scott Reid recommends copying these early cellulose-nitrate negatives onto safer film and destroying the originals in all cases where diplomatic analysis shows that it does not need to be kept for evidential purposes (Reid 1991), and Clark points out that if kept they should be removed to ventilated areas (1990: 42). Nitrate sheet film remained in use until about mid 1930s to early 1950s and was gradually replaced through the introduction of cellulose acetate in 1923, cellulose diacetate in 1937, and cellulose triacetate in 1947 (Messier 2005). Today, cellulose triacetate remains in use and was considered good archival quality until recent discoveries of instability (Messier 2005). Messier recommends films with a polyester base that were first introduced in 1955 (Messier 2005).
All cellulosic materials deteriorate through
similar mechanisms and preservation calls for sub-zero temperatures and
enclosures that pass photographic activity tests [††]:
"Environmental controls are
essential for the preservation of film-based negatives. It is clear that
typical ambient conditions (that is, approximately 40% RH and 70˚ F) are
not adequate for the preservation of nitrate and acetate material. Of
particular importance is the fact that once deterioration of a collection of
negatives begins, it gains momentum rapidly, leading to the swift destruction
of artifacts and increased health and safety risks." (Messier, 2005).
Stable negatives should be handled with lint-free cotton gloves, but deteriorated ones release harmful chemicals so should be handled with “neoprene gloves, goggles and a respirator” (Messier, 2005). Therefore, deteriorating negatives can be recognized by the smell, and should be immediately and continually segregated from the stable ones to prevent the acceleration of deterioration (Wilson Part 1 1998: 6). Transparencies (e.g.: 35mm slides), should be stored in polypropylene, polyethylene or polyester sleeves or carousel trays (Wilson Part 1 1998: 6).
[**] a fire in 1909 at the Fergusin Film Exchange Building in Pittsburgh prompted the National Board of Fire Underwriters to draw up regulations regarding the handling and storage of nitrate film (Messier, 2005)
[††] specified in ANSI Standard IT 9.2-1991
The chemical nature of silver analog prints and negatives implies a certain inevitable level of degradation and raises the need for copying and more recently digital conservation and restoration. Copying and microfilming can be an enormous challenge with negatives more so than with prints. Chris Woods describes a process that lifts the image layer of deteriorating cellulose diacetate negative from its shrinking (and so image distorting) base, to avoid the risk of the “complete loss of information within the next fifty to one hundred years” (1992: 46).
As long as the negatives are in good shape, it is possible to photo-reduce or digitize them. Ruth Kerns describes a preservation project for deteriorating photographic negatives at the Special Collections and Archives of George Mason University that used photo-reduction mechanism capable of producing microfilm directly from the negatives (Kerns 1988: 111). It is interesting to note that image enhancement through “contrast compensation” (Kerns 1988: 112) in the duplicate microfiche was considered to be one of the strengths of this approach. Even though digitization was noted as an option by the author in 1986, the National Archives and National Research Council - Committee on Preservation of Historical Records still recommended the use of micrographic processes for film at this time (Kerns 1988, 112).
The situation changes dramatically over the next ten years of technological innovation, turning digitization of photographic materials into a practical option for many institutions. Lynn Ewbank outlines some of the main advantages of choosing to undertake this option: reducing handling while at the same time increasing access to higher quality images than the photocopies of originals that the archive provided in the past, increased access in-house, across the country and around the world (Ewbank 2000:15-16). The Arkansas History Commission archive[‡‡] project described by Lynn Ewbank was successful in increasing access “because digital data represents a symbolic description of the originals and can be copied without loss, shared easily and viewed without pre-selection” while at the same time enhancing preservation (Ewbank 2002: 57). It is interesting that this particular project decided to use MARC as its metadata format (one record per image) out of the plethora of options[§§]. Cataloging and access are complex challenges requiring human resources and money, but “without a rigorous effort to develop an understandable, expandable, and reliable catalog system, a collection can lose its meaning and value” (Ross 1996: 10). Other decision include policies on file names and formats (e.g.: archival TIFF for preservation and low and high resolutions JPGs for display) as well as rules for cropping and tonal distribution (Ewbank 2002:53).
Roy McCrutchen outlines three types of questions that need to be answered before digitization: the intended purpose of the digital images (distribute prints, view online, distribute for publication), the type of originals (black & white, color, glass, tin, etc.), and miscellaneous (safety of originals, copyright, longevity of media, outsourcing vs. in-house, budget) (2000: 18). McCutchen recommends making photographic copy prints (to preserve original’s safety) and remarks that sometimes it is better to scan from prints rather than low density negatives (2000: 19). Among McCutchen’s other recommendations are Kodak Gold CDs for storage, Fuji Crystal Archive papers for printing and the use of printers that use gaseous RGB lasers such as LightJet 5900 (2000: 19).
Digital cameras capture images on a light-sensitive silicon CCD (Charged Coupled Device). Ross’ report on a yearly seminar on digital preservation [***] identifies resolution in addition to cost and format as “the most important considerations in matching the camera’s features to your project’s needs.” (Ross 1996: 9) Digital resolution implies a division into concrete blocks whereas some claim that analog images “have infinitely smooth variations between light and dark” (Ross 1996: 9). Scanning should be done at highest resolution available requiring large amounts of space. Mortensen states that “the resolution or information within, for example, a 300 dpi, 24.5 MB file of an 8" x 10" print is approximately one-tenth of the information that is in the original image” but admits that his definition of ‘information capture’ may become invalid (1998: 5). It is difficult to measure the quantity of information captured in digitizing since measures such as resolution tell only a part of the story, there are also qualitative changes that are a result of the dimensional reduction involved in moving from a physical object to a two-dimensional digital image: “visual cues embedded in original photographs are homogenized by digitizing into a unity of pre-determined size, quality and tonal range of the digital photograph” (Sassoon 1998: 10).
The digitization project of photographic material from a collection at the Royal Photographic Society (RPS)[†††] recommends a ground-up approach that takes image quality into account during the digitization process, an emphasis on retrieve-ability of the digital information in the future and storage media with long archival life (Birdsey 2000: 2-4). RPS digitized 35mm slides using a Nikon Coolscan that was grey balanced with the Kodak colour test target Q-60 on the same Ektachrome 35mm slide as the source and gamma adjusted for optimal tonal response to the thin images, producing 24bit files measuring 2482 x 3764 pixels 26.7 Mb in size (Birdsey 2000: 4). The files were processed using Matlab image processing, and stored as sRGB[‡‡‡] TIFF on ISO 9660 CD-ROMs (Birdsey 2000: 5).
Joanna Sassoon examines the relationship between photographs as unique physical objects and their digital reproductions and argues for a change towards a more provenance based approach towards documenting their collection: “photographs can be understood from the perspective of the technology which created them, the processes by which the images are revealed, the object itself, the trail of ownership through which it has been preserved, and how the institutions have acquired it” (Sassoon 1998: 5). The fact that multiple photographic prints are made from a negative only implies that the prints are multiple original documents. These documents carry information on the image, but they also carry evidential value through functional context and “a history of the truth of the image – the relationship between the structures which have served to create, authenticate and preserve an image” (Sassoon 1998: 8). The question that Sassoon poses should remain in the forefront of theoretical considerations of digitization of photographic materials: what are “the implications for research of devaluing the materiality of the photograph?” (Sassoon 1998: 13) and we should use the answers to improve the metadata schemas used to catalogue the digital surrogates.
[‡‡] this project is available today at <http://www.ark-ives.com/photo/>
[§§] the choice must be made based on the budget and circumstances, for a review of metadata schemas for images see Neugebauer, Tomasz. “Metadata for Image Resources” PhotographyMedia. 2005. 14. Nov. 2005. <http://www.photomedia.ca/article.php?page=1&article=AImageMetadata>
[***] “Preserving Photographs in a Digital World” was a 1996 seminar sponsored by Rochester Institute of Technology’s Image Permanence Institute <http://www.imagepermanenceinstitute.org/>, Technical and Education Center of the Graphic Arts and Imaging and George Eastman House <http://www.eastmanhouse.org/>. The seminar is available this year (2005) under the title: Preserving Photographs in a Digital World: Balancing Traditional Preservation with Digital Access <http://www.imagepermanenceinstitute.org/sub_pages/8page10.htm> (visited 19 Nov 2005)
[†††] Royal Photographic Society <http://www.rps.org/> (visited 19 Nov 2005) collection includes photographs by Nicéphore Niépce, William Henry Fox Talbot, Julia Margaret Cameron, David Octavius Hill and Robert Adamson, Edward Steichen, Roger Fenton, and Alvin Langdon Coburn (Birdsey 2000: 3).
[‡‡‡]
standard Red Green Blue colour space, for more information see
Michael Stokes Matthew et al. A Standard Default
Color Space for the Internet - sRGB 5 Nov 1996. <http://www.w3.org/Graphics/Color/sRGB
>
The sensitivity of photographic materials to its environment, including exposure to light leads to recommendations for separate storage and access environments, and the practice of providing copies of originals for viewing and digitization. The scans of the William Henry Fox Talbot collection were done from reproductions (35mm Ektachrome slides done in 1996) because the originals could not be exposed to light even for a few hours (Birdsey 2000: 3). Digital reconstruction preserves the information and content, but does not save the original material (Ross 1996: 9). In fact, digitization and making the images available to the public can increase demand for originals.
Donald Ross describes how a trained conservationist ‘repairs’ surrogate digital images of daguerreotypes through manipulation techniques that remove dust spots, clear chemical fog, revitalize motion pictures frame by frame, and more (Ross 1996: 9). This raises problematic issues for authenticity of the digital surrogate as a ‘reproduction’ of the original. It is reassuring that this problem is recognized by some digitization projects: The Royal Photographic Society requested that commercial image editing software not be used to manipulate or edit the digital files because of concerns about differences in appearance of original material and digital reproduction (Birdsey 2000: 5).
Photographs are unique documents with both evidential and information value, and the effort being put into preserving these documents is well worth it in historical currency. The fast pace of technological progress has become a great challenge for archivists that must remain on guard against trends that promise to ‘capture’ information directly and completely into new and ‘permanent’ media. In terms of practical and technical preservation, the black & white negative is still “the most permanent storage media for photographic images” (McCutchen 2000: 20). Furthermore, there is also a fundamental difference of form between the physical originals and standardized digital captures. Lorraine O’Donnell argues that the debate within the context of Canadian total archives approach over the relative importance of “intellectual content of graphic records over their physical appearance or form” (O’Donnell 1994: 106-107) has not adequately dealt with the full variety of record forms (1994: 106). I believe that we will continue to re-examine and expand the concept of form in light of digital images.
There has not been enough discussion about what is lost in the process of digitizing original photographs. Since a photograph is more than image itself, digitization is indeed a translation and transformation of state rather than a “transliteration of tones” (Sassoon 1998: 9). We are being just as naïve about the neutral, transparent and unmediated nature of digitization as we once were about the exaggerated authenticity of the first daguerreotypes. In balance, however, digitization does offer archives a new means of providing access and additional preservation options for photographic documents, as long we do not digitize “at the expense of long term preservation of the provenance of the collection or the physical object from which the digital source originates” (Sassoon 1998: 13).
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