Category Archives: Digitization Expertise

Digitization Details: Sidney D. Gamble’s Lantern Slides

I have worked in the Digital Production Center since March of 2005 and I’ve seen a lot of digital collections published in my time here.  I have seen so many images that sometimes it is difficult to say which collection is my favorite but the Sidney D. Gamble Photographs have always been near the top.

The Sidney D. Gamble Photographs are an amazing collection of black and white photographs of daily life in China taken between 1908 and 1932.  These documentary style images of urban and rural life, public events, architecture, religious statuary, and the countryside really resonate with me for their unopposed moment in time feel.  Recently the Digital Collections Implementation Team was tasked with digitizing a subset of lantern slides from this collection.  What is a lantern slide you might ask?

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Herding Ducks

A lantern slide is a photographic transparency which is glass-mounted and often hand-colored for projection by a “magic lantern.”  The magic lantern was the earliest form of slide projector which, in its earliest incarnation, used candles to project painted slides onto a wall or cloth screen.   The projectionist was often hidden from the audience making it seem more magical.   By the time the 1840s rolled around photographic processes had been developed by William and Frederick Langenheim that enabled a glass plate negative to be printed onto another glass plate by a contact method creating a positive.  These positives were then painted in the same fashion that the earlier slides were painted (think Kodachrome).  The magic lantern predates the school slate and the chalkboard for use in a classroom.

After working with and enjoying the digitization of the nitrate negatives from the Sidney D. Gamble Photographs it has been icing on the cake to work with the lantern slides from the same collection so many years later.  While the original black and white images resonate with me the lantern slides have added a whole new dimension to the experience.  On one hand the black and white images lend a sense of history and times passed and on the other, the vivid colors of the lantern slides draw me into the scene as if it were the present.

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Barbers on Bund

I am in awe of the amount of work and the variety of skill sets required to create a collection such as this.   Sidney D. Gamble, an amateur photographer, to trek across China over 4 trips spanning 24 years, photographing and processing nitrate negatives in the field without a traditional darkroom, all the while taking notes and labeling the negatives.  Then to come home and create the glass plate positives and hand color over 500 of them.  For being an “amateur photographer” Gamble’s images are striking.  The type of camera he used takes skill and knowledge to create a reasonably correct exposure.  Processing the film is technically challenging in a traditional darkroom and is made much more difficult in the field.  Taking enough notes while shooting, processing and traveling so they make sense as a collection is a feat in itself.  The transfer from negative film to positive glass plates on such a scale is a tedious and technical venture.  Then to hand paint all of the slides takes additional skill and tools.  All of this makes digitization of the material look like child’s play.

An inventory of the hand-colored slides was created before digitization began.  Any hand-colored slides with existing black and white negatives were identified so they can be displayed together online.  A color-balanced light box was used to illuminate the lantern slides and a Phase One P65 Reprographic camera was used in conjunction with a precision Kaiser copy stand to capture them.   All of the equipment used in the Digital Production Center is color-calibrated and profiled so consistent results can be achieved from capture to capture.  This removes the majority of the subjective decision making from the digitization process.  Sidney D. Gamble had many variables to contend with to produce the lantern slides much like the Digital Collections Implementation Team deals with many variables when publishing a digital collection.  From conservation of the physical material, digitization, metadata, interface design to the technology used to deliver the images online and the servers and network that connect everything to make it happen, there are plenty of variables.  They are just different variables.

Nowadays we photograph and share the minutia of our lives.  When Sidney Gamble took his photographs he had to be much more deliberate.   I appreciate his deliberateness as much as I appreciate all the people involved in publishing collections.  I look forward to publication of the Sidney D. Gamble lantern slides in the near future and hope you will enjoy this collection as much as I have over the years.

Post Contributed by Mike Adamo

Digitization Details: Re-Formatting Audio Cassettes

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A real live audio cassette!

The 310 oral histories that comprise the newly published additions to the Behind the Veil digital collection were originally recorded in the 1990’s to the now (nearly) obsolete compact cassette format—what were commonly called “tapes”.  The beauty of the compact cassette format was that it was small and portable (especially compared to the earlier reel-to-reel tape format), relatively durable due to its hard plastic outer shell, and most of all—could easily be recorded to at home by non-professional users.  This made it perfect for oral historians who needed to be able to record interviews in the field at low cost with minimal hassle.  

Unfortunately, the compact cassette format hasn’t aged particularly well.  Due to cheap materials, poor storage conditions, and normal mechanical wear and tear, many of these tapes are already borderline unplayable a short 40 years after their first introduction.  This introduces a number of challenges to our process of converting the audio information on the tapes into a digital file format that can easily be accessed online by patrons.  I won’t exhaustively detail our digitization process here, but only touch on a few issues and how we dealt with them.

Inspecting a tape
Our fearless audio digitization expert carefully inspects a tapes.

Physical degradation and damage to tapes: We visually inspected each tape prior to digitization.  Any that were visibly broken or had twisted or jammed tape were rehoused in new outer shells.  At least with this collection, rehousing allowed us to successfully play back all of the tapes.

Poor quality of original recordings: We also did a brief audio inspection of each tape before digitization.  This allowed us to identify issues with audio quality.  We found that the interviews were done in a wide variety of locations, often with background traffic, television, appliance and conversation noise bleeding into the recording.  There was no easy fix for this, as these issues are inherent in the recording.  Our solution was to provide the best possible playback on a high-quality cassette deck, a direct and balanced signal path, and high quality analog-to-digital conversion at the preservation standard of 24 bits, 96.1 kHz.  This ensured that the digital copy faithfully reproduced the audio material on the cassette, warts and all.

Other errors in original recordings: There were some issues in the original recordings that we opted to fix via digital editing or processing in our files for patron use (while retaining the unaltered preservation files).

  • In cases where there was a significant gap of silence in the middle of a tape, we edited out the silence for continuity’s sake.
  • In cases where there were loud and abrasive clicks, pops, or microphone noise at the beginning or end of a tape side, we edited out these noises.
  • Several tapes were apparently recorded at the wrong speed, resulting in a “chipmunk voice” effect.  I used a Speed/Pitch function in our audio capture software to electronically slow these files down so that they play back intelligibly and as intended.
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Audio digitization deck

Another challenge, common to all time-based analog media, is the cassette tape’s “real-time” nature.  Unlike a digital file that can be copied nearly instantaneously, a 90-minute cassette tape actually takes 90 minutes to make a digital copy.  Currently we run two cassette decks simultaneously, allowing us to double our throughput.

As you can see, audio cassette digitization is more than just a matter of pressing “play”!

–post written by Zeke Graves

Still want to learn more about the Behind the Veil collection of oral histories?  Check out coverage of the collection over at Rubenstein Library blog, The Devil’s Tale.