Amelanchier Canadensis

The Warren H. Manning (1860-1938) architectural landscape lantern slide collection is now available through our digital collection.  Nearly 1700 images of botanical specimens, landscape drawings, and examples of gardens, cityscapes, and natural landscapes, are represented.

Manning was a pivotal figure in the history of American landscape architecture and a co-founder of the American Society of Landscape Architects.  He developed an environmental planning model based on the concept of gathering and organizing discrete types of environmental data, such as soils and vegetative cover, in mapped form.  This evolved into Manning’s National Plan, a document representing an early attempt to provide a statistical profile of the entire country and a land classification system that could be used by the government to control the exploitation of natural resources and to evaluate scenic beauty.  The Manning collection in our Special Collections includes, among other things, many black and white as well as some colored lantern slides which have been scanned to preserve their fragile images and to make them available to be viewed by everyone online.

Acer japonicum macrophyllum

Lantern slides are scanned differently from other items in a few ways.  They are a transparency and it’s not always immediately obvious or marked which side is the front, so some examination of the slide is necessary to present the image properly and not backwards.  Since the slides are only 3 x 4 inches and the images on them are sometimes much smaller, they were scanned at a very high resolution so that all the details show when the image is viewed on a standard computer screen.  There is also the ability to zoom in for greater detail.  The images were cropped leaving the black tape boarder around them to preserve the look of the original and to show that the digitally scanned image actually came from a lantern slide.  Since this group of slides was collected by Manning over a long period of time and from different sources, there was a wide variety of quality in the images and therefore the contrast and brightness had to be adjusted quite a bit in some slides in order to see the images in what would be the most realistic way possible.

Rhododendrons on the William Rockefeller estate

Like photographs, lantern slides are layered structures.  They are composed of a glass support layer, with an image-forming material (usually silver particles) embedded in an emulsion layer that has been adhered to one side of the glass.  In some cases, a second sheet of glass is laid over the emulsion layer and attached to the lantern slide by wrapping the edges with binding tape.

Other than breakage of the glass support, the most common type of deterioration for lantern slides is loss of the emulsion layer.  This damage can be caused by poor handling of the slides, or by storage in an environmentally unstable environment.  Natural skin oils can leave marring fingerprints on the slides, and rough handling can cause abrasions to the image surface.  As the relative humidity of the environment fluctuates, the emulsion layer can swell and contract in response.  This swelling and contracting can then result in the emulsion peeling or flaking away from the glass support.  Since the emulsion layer is what binds the image-forming particles to the glass, loss of emulsion means loss of image.

Now that these slides have been scanned there is less need to bring them out reducing the risk of breaking, scratching, and exposure to environmental change.  The scanned images are much easier to use and can show more detail with zoom capabilities than the lantern slides themselves.

Update:  A more comprehensive version of this blog post has been published as an article in the June 2011 issue of Microform & Digitization Review.

Bill Yungclas and Melissa Tedone, “Digitizing Lantern Slides in the Warren H. Manning Collection,” MDR, Vol. 40, pp. 68-70, June 2011.