The Minnesota Historical Society’s Local History Services helps Minnesotans preserve and share their history. This blog is a resource of best practices on the wide variety of museum, preservation, conservation, funding, and non-profit management topics. We’re here to help.
Scanning Negatives and Slides
In order to provide better access, get a better idea of what is in a collection and to better preserve images on fading and deteriorating film it is important to digitally scan slides and negatives and to add the proper metadata.
It's never too soon to start preserving your slides and photos, and in some cases it may already be too late.
Conditions you can find slides and negatives even if they have been in unopened boxes or untouched sleeves:
- Slides and negatives which are stuck to their sleeves
- Snowflake crystal-like artifacts on film
- Film developed by drugstore-type services, fading very badly, where the same type of film processed at the same time by different vendors can be fine
- Dark Fading or Light Fading (see below)
Clean Before Scanning
Microscopic specs of dust become boulders and tiny hairs become tree limbs when scanned at 2400 dpi. Newer scanners can use technology to "remove" the dust scanned on with the image. However the dust is not actually removed rather it is modifying the image to hide the dust. Dust and dirt ideally should be removed before scanning.
- Wear surgical gloves when handling negatives or slides. Even if finger prints are not visible grease from fingers can cause problems years down the line.
- To remove simple dust before scanning clean using compressed air, an antistatic brush, and careful attention.
- For slides with serious problems like finger prints use Pec-12 and Pec Pads.
- The best solution would be to never get the slides dirty and with careful storage dust and damage can be mitigated. However even slides that have never left their box or envelope seem to accumulate dust.
Flatbed Scanner or Dedicated Slide Scanner?
As recent as a few years ago there was a great difference in quality from a dedicated slide scanner versus a flat bed scanner with a slide scanner attachment. However, quality of what you can get from a flat bed scanner with a slide scanner attachment has improved to the point that most are buying flatbed slide/negative scanner combinations and many slide scanner producers like Nikon have simply stopped making dedicated slide scanners. The other nice thing is that with the increase in quality there has been a corresponding significant drop in price of scanners. There still is at least a couple of companies still making slide/negative scanners and if you have hundreds or thousands of slides and negatives or are dealing with professionally taken/processed slides and negatives it would be a worthwhile expense (currently around $400) to purchase a dedicated slide/negative scanner.
One advantage of a flatbed slide/negative scanner combination is that not all negatives are 35mm and many can scan a large variety of sizes of transparencies. However you have to do the research to see just what each model supports.
While a flatbed slide/negative scanner combination is acceptable, other scanners are not. Document scanners, Microfilm Reader/Scanners and the all-in-one copier/scanner/faxing machines either lack the resolution, the optics or both for doing archival quality scans.
Another issue is the age of the scanner. Like computers, scanners have improved to a point both in quality and price that it is really worth looking at retiring an older working scanner. The example on the left below comes from the Minnesota Historical Society's own scanner in the SHPO office. The scanner was purchased in 2001 and still works very well. However, the highest DPI is 2400 which is inadequate for many 35mm slides and the optics are far from perfect when compared to a newer 2011 model scanning at the same DPI.
|2001 Flatbed Scanner|
|2011 Flatbed Scanner|
Dark Fading | Light Fading
Remember that resolution isn't everything. Color and contrast are equally important and dealing with older slides and negatives you will run into the issue of fading. Slides and photos will fade for a variety of reasons. All dyes have a limited lifetime because they break down because of temperature, light and chemical reactions to materials within the dyes themselves.
Dyes that fade when they are in the dark is termed "Dark Fading" and dyes that fade because they are exposed to light is termed "Light Fading.
Light fading is caused by exposure to high intensity light such as when a slide is shown in a slide projector. Magenta dyes will typically fade the quickest.
Dark Fading occurs when your slides are not exposed to light. It is caused by a temperature and relative humidity reaction. Cyan dyes will typically fade more quickly. Prior to the mid-1980s, the Cyan dye was particularly unstable. BTW: It is important to understand that Dark fading is not caused by darkness, Dark fading simply refers to the fading and staining that take place in a color material during storage when light is not present.
Digitally Fixing Fading
Improvements in software have made color and contrast correction remarkably easy with "auto correction" tools with are often available with the scanning software. However, true color correction and digital restoration is both and art and a science, to get the best possible results hire a professional with experience in color correction and digital restoration.
NOTE: It is important to understand that your unmodified raw scanned image is your master image. Contrast or color corrections to the image will make it a derivative of the master image since correcting the image introduces changes that are subjective AND unreversable. However if the image needs major correcting it is acceptable to archive a corrected derivative to along with the unmodified master image so it can be used to create further derivatives.
Slide and Negative Preservation
Since negatives and slides are original source information it is important to keep them as long as they remain a viable source. With proper care and storage certain filmstocks can store unchanged for decades. Unfortunately film preservation is out of the scope of this article. However Wilhelm Imaging Research, Inc. has extensive articles on slide and negative preservation. Founders Henry Wilhelm and Carol Brower Wilhelm literally wrote the book on slide and negative preservation.