Charles W. Cushman Photograph Collection
  Indiana University Archives / Digital Library Program

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Color Restoration

This story was written by Jenn Riley, Digital Media Specialist for the Digital Library Program, and was adapted from an article originally published in the Fall 2002 issue of The Source, an Indiana University Libraries quarterly newsletter.


When archivists discovered a suitcase full of early Kodachrome slides in an annex of the IU Archives, we unknowingly began an international adventure. The slides were visually stunning and painstakingly documented. Charles W. Cushman, an IU alumnus and amateur photographer, had willed to Indiana University almost 15,000 slides taken between 1938 and 1969. Mr. Cushman traveled all over the world, and his photographs revealed a wide range of subjects, from architecture to botany to twentieth-century urban life.


Unfortunately, color film is not permanent, and some of Cushman's slides were showing their age. The cyan, magenta, and yellow dyes used to print the image onto film fade over time. Early Kodachrome color slide film, from the time of its release in 1935 until the film and processing methods were modified in 1938, fades and becomes red. This phenomenon, called "red shifting," affected over 250 of the slides in the Cushman collection.

Original image, before restoration
[Before]

Although it is possible to restore the dyes to black and white film, this is not possible with color materials. Conventional digital imaging methods, likewise, cannot restore badly discolored images. Too much data is irretrievably lost. A film scanner with a skilled operator simply cannot recreate original image information that, with the dye on the slide, has faded over time.


We sought expert advice. The Abteilung für Bild- und Medientechnologien, Philosophisch-Historische Fakultät (formerly the Abteilung für Wissenschaftliche Photographie [Department for Scientific Photography], part of the Institut für physikalische Chemie [Institute of Physical Chemistry]) at the University of Basel in Switzerland, has done research into modeling the fading patterns of the dyes of many types of film. Under the direction of Dr. Rudolf Gschwind, technicians use known fading patterns to recreate mathematically what the dyes on the slide might have been like at the time of processing. As part of the project to digitize and provide access to Mr. Cushman's materials, the Digital Library Program sent 256 slides to the lab in Switzerland for color reconstruction.


The results are nothing short of amazing. From the almost monochromatic red-shifted images, we received digital images and copy slides whose colors rival the rest of the collection. The procedure, of course, is not perfect. The exact fading properties of historical films cannot be known because there no longer exists any undeveloped film to test both in its unfaded and faded states. There are also other factors affecting the fading process, including how the image was stored. The oldest slides from the Cushman collection not only have faded badly, but have dirt, mold, and masking on them that has affected the fading of the dyes. Many of the reconstructed images still show areas where dyes faded differently.

Image after restoration
[After]

The project has been funded, in part, by a National Leadership Grant from the Institute of Museum and Library Services. The knowledge we have gained from color slide preservation will serve as a model for other archives and library throughout the country.


More information about the restoration, including some technical papers on the process, can be found at the Abteilung für Bild- und Medientechnologien's web site, http://www.abmt.unibas.ch/index.php?content=forschung.html.