Photographic format sources in OpenSFHistory

Digital images on OpenSFHistory are created from many types of original photographic material. Here we detail some of the formats.

Glass Plate Negatives
(catalog numbers beginning with wnp15)

Glass plate negatives were in use by both amateur and professional photographers from the 1850s until the early 1920s. Examples in OpenSFHistory date from the 1880s, and sizes range from 8×10 inches to 2×3 inches. To date, we have cataloged over 800 glass plate negatives.

Glass Plate Negatives
A glass plate negative viewed on a light table.


Nitrate Film Negatives
(catalog numbers beginning with wnp14)

Nitrate negatives are a plastic film in use from about 1895 until the 1940s when safety film largely replaced it. Most amateur film up though the end of the 1930s is nitrate film. Nitrate film is highly flammable, but will not combust spontaneously under normal environmental conditions. Nitrate film was still in production up until the 1950s and it can be difficult to identify. If we’re not sure about the chemical composition of a film negative, to be safe, we treat it as nitrate. After scanning, these items are vacuum-sealed and put into cold storage. To date, over 1,000 have been processed and put online.

Nitrate negative
A nitrate negative


Safety Film Negatives
(catalog numbers beginning with wnp28)

Beginning in the mid-1920s, nitrate film began being replaced with cellulose acetate film known as “safety film.” While more stable and less flammable than nitrate, safety film does deteriorate, and can become acidic, shrink, and degrade (a vinegar smell is a big tip-off). So far we have cataloged over 500 negatives.


Lantern Slides
(catalog numbers beginning with wnp13)

Lantern slides are mounted glass positives. They were mostly produced commercially for sale and were intended for projection on a screen, either in the home or in a theatre. They are the precursors to 35mm transparency slides popular from the 1940s to the 1970s. We currently count 272 lantern slides in the collection.

Lantern Slide
Lantern Slides


(catalog numbers beginning with wnp24)

Stereoviews, or stereopticon cards, are commercially-produced dual exposures mounted on cardboard for viewing with a special viewer to produce a three-dimensional effect. They are the precursors to Viewmaster reels of the 1950s and 60s. We have not digitized any stereoviews at this point.



35mm Slides
(catalog numbers beginning with wnp25)

Primarily Kodachrome, 35mm positive transparencies in the collection date from the late 1940s though the 1980s. We currently have about 400 online.

35mm slides
35mm slides


Copy Negatives
(catalog numbers beginning with wnp26 and wnp33)

Copy negatives are pictures of pictures. There are many, many copy negatives in the collection, so many that we have separated them into multiple catalog numbers. These images have many sources, from city agencies such as the Department of Public Works and San Francisco Water Department (PUC); institutions such as Society of California Pioneers and California Historical Society; and individual collectors and families who allowed their photos to be copied. The bulk of this type of negative are still in the process of being cataloged and digitized.

35mm copy negatives
35mm copy negatives


Duplicate Negatives

Duplicate negatives are created in a darkroom by a process where positive film is exposed to a negative, resulting in another negative. Often this is accomplished as a contact exposure, where an exposed negative is laid directly onto film and exposed to light. Identifying duplicate negatives can be a challenge and some dupe negatives have been processed.

Original Prints and Scrapbooks
(catalog numbers beginning with wnp27)

Acquired through purchase and gifts, these items are mostly amateur photography and family photos, though a small amount of commercial photographs exist in the collection.

Original Prints
Original Prints


Contemporary Prints
(catalog numbers beginning with wnp4)

The private collector, whose collection is the cornerstone of OpenSFHistory, was an accomplished photographer and darkroom technician who made prints from many sources for reference, sharing, trading, and for sale. Often other collectors lent items for this purpose. The collector stored most negatives with one or more reference prints. Boxes of prints arranged by location were loaned out to other collectors or historians for scanning or duplication. Many of the prints in the collection are duplicated by original or copy negatives extant in the collection, but in some cases the negatives from which the print is derived was borrowed and returned. We avoid scanning contemporary prints unless we are sure that the negative doesn’t exist in the collection.

Contemporary 8x10 Prints
Contemporary 8×10 Prints

Western Neighborhoods Project and the Private Collector

reprinted from SF West History – the member newsletter of the Western Neighborhoods Project

You know the name. If you have spent any time looking at historical photos of San Francisco in the past thirty years, you’ve read it. At this point in his life this collector of San Francisco imagery doesn’t want any more publicity. For the past few years his policy has been photos should be cited as “Courtesy of a Private Collector.”

At the Western Neighborhoods Project we have had a long relationship with this private collector, gratefully accepting images to help illustrate the history of the city’s west side. Almost every major collection of San Francisco historical photos has passed through his hands at some point.

Early in 2013 he approached us about taking stewardship of his collection, to catalog, digitize, preserve, and make it available to the public, both physically and online. We were shocked and excited. The collection amounts to thousands of images in many forms. Together, the recent 8×10 inch prints; acetate, glass, and nitrate negatives; cabinet cards; panoramas; postcards; scrapbooks; yearbooks and other items tell a story of one person’s passion for San Francisco’s past.

“It’s too much, “we thought as we eyeballed the more than twenty-five file cabinets holding most of the collection. The sheer volume was intimidating for a volunteer-run organization with a small annual budget and limited physical space.

We faced and equally-daunting situation in 2002, when we had the opportunity to save four 1906 earthquake refugee cottages on Kirkham Street. Uncertain we could pull it off, we tried anyway. And we succeeded.

So we came up with a plan. We’d do a pilot project with just a small portion of the collection. We decided to tackle the images of the Cliff House, Sutro Baths, Sutro Heights, and Ocean Beach areas. We would sort, rehouse, catalog, digitize, and put online this first installment, then step back to assess the effort, costs, and rewards.

We accepted the first few boxes early last summer (2014): 1600 8 x 10 inch prints (amounting to about 1100 individual images) and another 40 or so glass and acetate negatives. Everything has been digitized and put online. The results are amazing.

Much of the material was compiled from other local collections, but a lot is new to even old hands like us. Local Historian and former National Park ranger John Martini and others have been helping us go through it all.

“Most of the historic photos I looked at were totally unique to me (and I’ve looked at a LOT of San Francisco photographs)… The number of photos is absolutely breathtaking, if not overwhelming. I felt like I kid in a candy shop.”

What’s next? Our pilot project is complete. (We are still adding titles, descriptions, and other metadata.) We will regroup with the private collector and our board of directors to draft a plan moving forward. We will keep the membership involved and informed along the way, but any future WNP has with the rest of this amazing archive will mean some serious fundraising. If you have any resources you believe may help, let us know.