You know those dusty boxes of photographs you’ve been meaning to put into an album? Or the shelf full of videotapes of the kids growing up? The glass-plate slides your dad took on vacation? Or even the 8mm film reels of you taking your first steps? Well, they’re not going to be around forever! Those memories of yours are all in analog format, which gives them a shelf life of about ten to thirty years – not long enough to hand down through the family over the generations.
Archival Stability of Analog versus Digital
First, what are the differences between analog and digital and why should you transfer your tapes and photographs? In analog recording, the signal recorded on the audio or video tape is a representation of the signal originally heard or seen by the microphone or video camera. It sends signals in a wave of reflection similar or “analogous” to the original signal.
The one advantage of analog recording for archival purposes is that the deterioration over time is gradual and discernible, allowing for transcription before reaching a point where it has degraded to an unusable level. Drawbacks? The quality of the duplicate will not be as high as the original because every time it is copied the original information signal is copied along with any tape or electronic noise. Also, the medium of tape itself is not particularly stable because of its layers of magnetic particles, binders, and backings. Photos on paper are acidic and will deteriorate as well.
In digital recording, the audio or video source signal is “digitized” – the signal is sampled at particular points along the wave and converted to a number that reflects the intensity of the signal. This is done by using a binary numbering system. On playback, the numbers are read and used to reconstruct the original signal. A digitally recorded tape will show little, if any, loss of quality when copied. The binary numbers (ones and zeroes) are read from and written to the tape. These numbers are distinguished from the background noise, whereas the analog recorder cannot tell the difference between background noise and the recorded signal, thus recording both.
Digital media can be viewed in a variety of ways: computer, movie screen, or by printing onto paper. It also allows for more and better manipulation of the image – change the size, add another image to the photo, improve color quality, etc. Even those faded Ektochrome slides from 50 years ago can have the colors adjusted and restored! But this manipulation also creates a drawback – the image can be manipulated or altered without recognition – not a good thing when it comes to government documents or when offered as evidence in court.
Storage and Care of Analog and Digital Media
Analog media include audio and video tapes, photographs, film, books and audio cassettes. All these can be transferred and stored onto a digital medium, such as compact discs (CD), digital audio tapes (DAT), or digital video (DVD), computer files such as JPEG, WAV, and AVI, extending their shelf life. There are ways to extend their usefulness until you decide to transfer to digital:
- Use and store magnetic tape reels and cassettes in clean environment. Clean your VCR, store tapes in dust free containers, rewind your tapes, keep photos in a covered box or album.
- Avoid fingerprints, food, or smoke, near the media.
- Keep tapes and photos out of strong light.
- Avoid drastic changes in temperature and humidity.
- Use buffered and/or acid-free storage whenever possible.
Some of the items above are pretty obvious, but most people don’t think about caring for them. It won’t solve their inevitable deterioration but will prolong their life until you transfer to digital media. Digital storage requires less space, and in addition to the above, these precautions should be taken:
- Lower light or use ambient light.
- Provide air circulation around the exposed medium.
Preserving Our Cultural History
Your family memories are not the only ones that need preserving. Museums, libraries and cultural organizations are rushing to record images of antique photos, maps, paintings, and other important historical media onto digital format. These institutions have always tried to find better ways of preserving artifacts by monitoring humidity and temperature, storing objects in archivally correct containers, and generally creating a safe environment to add longevity. Obviously, we cannot transfer all of these items to digital format. But we can make digital copies in film or photo or sound to monitor their conditions. Digital preservation is important to an archivist because it reduces the amount of time an object has to be handled, alleviating the “wear and tear” factor. But the most wonderful reason to put as many objects and artifacts into digital format is so that they can be made available for viewing by the general public in museums, libraries, schools, and other institutions. These “digital surrogates” are great teaching tools, bringing the history and beauty of the objects to those who might not otherwise have a chance to see them.
The Library of Congress is making efforts to create a national digital library, including archival collections, texts, images, sound files, full-motion video, and other document types. The Museum of Television & Radio in Los Angeles has sound and tape archives to be restored and preserved. The National Digital Library Program (NDLP) is well on its way to its goal with thousands of books and works on paper already in digital format.
Digital Imaging and Conversion
Digital images should compliment, rather than replace other formats. Quality and clarity of the image should be of the highest priority when creating a digital image for archival usage, while optimizing the potential for longevity. Different media types require different techniques for digital conversion. An illustrated manuscript or old map will require an overhead file format. This same resolution can be used for three-dimensional objects to be represented in two dimensions. Large old photos to be reproduced require 24-bit, 4096 x 6144* resolution and TIFF archive file format. A drum scanner can be used, depending on the size of the photograph. Transparencies are scanned at 600dpi so that they can be enlarged as a print without losing quality. A document 10-inches across scanned at 600dpi requires 6000 pixels. A 5-inch tintype scanned at 300dpi requires 1500 pixels.
Legibility and clarity of the digital image results from a combination of resolution and a bit of depth. Resolution involves the number of pixels or dots per inch (dpi) – the more pixels, then the more detail. And the higher the resolution the larger the file size. Digital file storage can require large amounts of physical storage. The use of compression can reduce this storage space. Storage types include: JPEG Screen Presentation Format, PDF Portable Digital rescue efforts continue. Realizing that digitizing artifacts won’t actually preserve them physically, it will still make available to many people the hidden treasures held in museum storage vaults and rarely seen by the general public. And also realizing that the technological obsolescence of the digital format is probably just around the corner, we will continue to prepare for different ways to preserve those precious memories and our cultural history.