The Electronic Media Review, Volume Four: 2015-2016
Tate has a collection of twenty-seven slide-based artworks, ten of which use synchronized slide projectors. A project was started in 2014 to explore the technical challenges of these ten synchronized artworks. The key aim of the project was to enable an improved understanding of the coded signals used for the crossfading, slide transitions, and timings of synchronized slide-based works in the art collection, in order to inform Tate’s collection care strategy.
Through the project, we researched and reviewed the synchronization control systems in terms of differences and compatibility. The main finding was that the translation between different systems was not reliable, and therefore we will aim to support all the systems present in the collection for as long as possible. Furthermore, an outcome of the research was to improve cue track identification and to make recommendations on capturing this information for the future. This paper presents an overview of the research carried out and considers practical options for the preservation of these works.
Tate has a collection of twenty-seven slide-based artworks, ten of which use synchronized slide projectors. The project was started in 2014 and circa 30 days were allocated to it over 18-months to explore the technical challenges of these ten synchronized artworks. This was initiated as a review into the methods of showing these works in the future following on from previous research at Tate into slide preservation (Weidner 2012). Tate’s strategy for managing its slide-based collection following on from the Dying Technologiesresearch project in 2011–12 is—where in accordance with the artist’s specification—to create digital images of each slide-based artwork, working with the artist to digitize the original transparencies and where they represent the best available master set (Weidner 2012). Tate’s current strategy is to display these works in their original formats, but as the obsolescence of both the synchronizing and slide technologies continues, we have begun to explore options for how to reproduce and present these works using modern technology. To ensure this representation is possible in the future, it became crucial to understand the coded synchronization signals for the ten synchronized works within our collection. This would ensure a better understanding, and more accurate capture, of the coded signals used for the crossfading, slide advancement, and timings for each synchronized slide-based work.
During the 1970s and 1980s, slide-tape artworks emerged from the expanded cinema practice where artists embraced this relatively low cost means of creating visual narratives using slides and audio (Vivid Projects 2013). This practice would be later abandoned by most in favor of video technologies, as advancements in computer operating systems enabled transition into a digital realm (Fogerty 2011). Slide-tape technology provided new possibilities for installation art, as one could employ two or three projectors at one time, and was being used by key emerging artists of the time, such as William Furlong (b. 1944), Ian Breakwell (b. 1943), Nan Goldin (b. 1953), KwieKulik (1971-1987), Black Audio film Collective (1982–1998), and James Coleman (b. 1941).
This technology originated in the audio-visual industry, where it was referred to as Multi-image presentations (Wikipedia 2016a). These more commercial applications shared the same hardware, but were typically more advanced in scale and complexity than those found in the experimental art community. For the programming, sophisticated switching devices were used to great effect along with banks of projectors.
Kodak introduced the first carousel slide projector in 1961, and by 1975, companies such as AVL (Audio Visual Laboratories) were producing programmable controllers to further automate the carousel movements and lamp brightness. Early control devices, such as the AVL Show Pro or the Clearlight 1500 Programmer, used punched tape as a basic form of memory. These would typically cost in excess of $1500 (Mesney 2000; Benedict and Fuller 1975). By the 1980s dissolve control devices using solid state electronics were being developed, allowing slideshows to be programmed in a variety of ways. Companies like AVL, Dataton, Electrosonic, and Arion all produced different (mostly incompatible) systems using proprietary coded control data with names such as Mate-trac, Syncode, Sync-Lock, PlusTrac, FreeTrac, and PROCALL.
As this technology advanced, computers were used to program slideshows, and two popular systems were AVL’s Eagle II computer and Dataton’s TRAX software, although both are now obsolete and unsupported.
The AVL Eagle II computer pre-dates Commodore and Apple, and runs the software PROCALL. AVL used a proprietary timecode called ClockTrak, which is digital control data that can be recorded as audio; it is similar to (but incompatible with) the widely used timecode SMPTE. The computer is used for programming only and is not required during display as the control data (cue track) can be played back independently (Wikipedia 2016b).
The Dataton TRAX software runs on the discontinued Mac OS 9 operating system (1990–2000). TRAX was designed as a multi-media control system which could interact with devices beyond slide projectors such as DVD players and lighting systems. TRAX has a graphical user interface with a linear timeline for programming cues. TRAX is similar to the AVL system in that it also outputs control data as audio so that the computer can be substituted by a CD player or similar device for display (Fahl 2016).
By the late 80s-early 90s Harvard Graphics—one of the first presentation programs—arrived, Microsoft released the first version of PowerPoint and significant advances were made with LCD projectors, which in conjunction with the digital photography revolution, contributed to a decline in the commercial demand for 35mm slides. In 2004, Kodak ceased production of slide projectors due to disappointing sales in 2003 (Global Events Consulting 2016).
SLIDE SYNCHRONIZATION SYSTEMS
This section describes how the Dataton system functions, as well as the key differences to the AVL system, which comprise two of the three systems primarily used at Tate. Both systems require an initial programming step, which includes designating the projectors and either inputting the commands (fade in, fade out, change slide, etc.) by code if using an AVL Genesis, or arranging the commands on a timeline in Dataton TRAX, before exporting the sequence to tape to create the cue track.
Once ready for display, the system’s core is the dissolve control unit and the cue track it receives to operate each slide projector. Figure 1 illustrates a basic display set up of a synchronized slide-based artwork (Fogarty 2011). The diagram shows two channels of audio. One channel of audio is sent to the amplifier and contains the soundtrack, which is heard in the room via the loudspeakers. The second audio channel, which is a tone with binary data, is played into the dissolve control unit to run the slide-show in time with the soundtrack. The slide control device reads the electronic pulses sent from the cue track and actuates the correct switches (Benedict and Fuller 1975).
SYNCHRONIZED SLIDE-BASED ARTWORKS
As mentioned in the introduction, the focus for the slide synchronization project was the group of ten works that require synchronization of multiple channels with a soundtrack (fig. 2).
For three of those 10 artworks, the synchronization had been defined by the artists in a system-independent fashion, and meaning that transfer to different systems is easier and the risks for future display are lower. The aims of the project were to:
-Identify the synchronization systems for each individual work.
-Review the control systems in terms of differences and compatibility
-Identify the cue track
-Make recommendations on capturing this information.
A series of practical tests were conducted using the synchronization tones provided with each artwork. These tests were run to ensure playback was still possible for all of the synchronized works for which Tate had either been supplied with a cue track or had made a cue track in-house. These practical tests identified three distinct systems associated with the seven artworks: Dataton, AVL, and Stumpfl (fig. 2). During these initial tests, it was determined that the Dataton system could be used to playback all of the cue tracks in the Tate collection excluding Baumgarten (b.1944), I Prefer it There Better than in Westphalia—ELDORADO (1968–1976 Tate, acc no. T07869), which currently is only compatible with the Stumpfl controller. Despite the ability of Dataton to interpret an AVL cue track via a device called a TRANS PAX, it was important to assess how accurately this could be achieved. Leading on from the initial tests, the decision was taken to focus on the AVL and Dataton in more detail, rather than Stumpfl (Wings Platinum) due to the number of devices present in Tate’s slide tape facility and the associated expertise and time available.
AVL AND DATATON COMPARISON
A comparison test between the two control units was set up. This test used two pairs of Kodak 2050 SAV projectors. One pair of projectors was controlled by an AVL Dove controller and the second pair was connected to the Dataton Pax controller using the TransPax to interpret the signal being sent (fig.3).
A group of test slides were used in the comparison test, with the same cue track played into both systems, in this instance this cue track was from a work by James Coleman (b. 1941): Living and Presumed Dead (1983-5, slide, 35 mm, 167 slides, 3 projections, color, and sound, Tate, acc. no. T07076). James Coleman has expressed a clear preference for AVL in his display specifications and it was important to compare any differences in how the two systems would handle the same slide show cues (Coleman 1996; Vitale 2001).
Initial observations suggested that some of the Dataton PAX fades were either slightly longer or shorter when compared to the AVL Dove, even when using the same cue track. This may point to differences in the dissolve curves on each device. The fades times varied by approximately half a second in response to particular commands. This was not consistent throughout the show as other fades matched precisely. This may not be an issue for all artworks, but it could affect the accuracy of the synchronization between sound and image. It should be noted that the cue track used in the comparison was native to the AVL system, and the Dataton TRANS PAX unit was required to translate the signal in real-time for the Dataton PAX controller.
It has not been possible to diagnose exactly why this difference exists between the two systems, but Pip Laurenson recalls a discussion with James Coleman where he described the AVL Dove x2 as having a more precise and immediate control over the lamp filament, which may well explain this variable response time (Laurenson 2016).
A recent email correspondence between Pip Laurenson and Aebhric Coleman, James Coleman’s son, (2016) revealed the following:
In the early 2000’s, I did a “shoot-out” comparison with Dataton and Dove X2 for the artwork Charon (MIT Project) (1989), which incidentally is in the collection of Tate. The Dataton on paper, and by very confident assertions of their main supplier in Ireland, would translate the cues correctly. However, it only worked for the simpler ones—the more complicated dissolve sequences did not work at all and the timing also went out of sync. (Coleman 2016)
The result of the tests was that the systems behave differently and the transcoding between systems is not accurate. Given the observed difference, it remains important to maintain at least two to three different control systems in use in the Collection.
CUE TRACK IDENTIFICATION
Cue track identification is critical as it enables the playback of slide-based artworks. In some cases, cue tracks will have been recorded in real time with the various slide changes and dissolves, etc., essentially creating the score to the sequence and corresponding directly to the soundtrack we hear. It is of course possible to preserve the cue track recording itself but its meaning is lost without the ability to replay it through the correct system or decode it based on our knowledge of the relevant system.
Because the cue tracks were identified as an area of vulnerability for synchronized slide-based artworks, it was important as part of the project to explore the cue tracks for each of the seven artworks. To assist with identification, it was helpful to consider specific characteristics of different tracks, such as:
-If one listens to cue tracks from different systems, do they sound different?
-Do they look different when imported into audio software that can display the waveform?
For most of Tate’s collection works, it was possible to identify the relevant control system for each cue track from the labelling or documentation associated with each work, and confirmation was achieved by testing each one with the relevant equipment.
CASAS ALTERADAS EXAMPLE
During testing, one particular cue track was proving to be very elusive, namely for Casas Alteradas by Armando Andrade Tudela (b. 1975) (2006, slide, 35 mm, 160 slides, 4 projections, color, Tate, acc. no. T12771). According to the artwork documentation (Weidner 2010), the piece can be shown using both Dataton and Stumpfl control systems. Despite having a version of the sync tone on a CD, it was not entirely clear for which system it was intended to be used with. Various tests were conducted using the Tudela cue track by attempting to control slide projectors with the three systems available, but none responded. Despite having the timing instructions well documented, it was important to positively identify the cue track as this sequence timing had been approved by the artist when the work was displayed previously.
The results of the testing also demonstrated that there are various factors that can mean a system does not run correctly. Critical to the running of the systems is its configuration.
Examples of this would be cabling issues, audio channels switched left/right, projectors not assigned correctly, control devices configured incorrectly for a specific model of projector, or in the case of a TRANSPAX, selecting the wrong input code setting.
It became apparent when listening to the cue tracks that there were audible similarities and differences. This lead to further analysis using the audio editing software Audacity, which enabled observations of distinct characteristics by viewing closely the linear graphical depiction of the waveforms. When comparing the Tudela cue tone with a working Dataton cue tone, it was clear that they had a very similar shape, but the amplitude was different. They also sounded very similar, but the Tudela tone was louder. By decreasing the gain to 2.5db, it was possible to confirm that the Tudela sync tone was indeed made for the Dataton system, but had been recorded too loud to be played at line level (fig 4).
By going through this processes, we confirmed that it is possible to identify a cue track by its sound and waveform, which may be useful if trying to source equipment.
REVERSE ENGINEERING POSSIBILITIES
A synchronized slide-based artwork is unlike other forms of media such as film and video. The difference is that the instructions or score set out by the artist are recorded in the form of a coded audio cue track that is proprietary to the system being used. If it is indeed possible to crack these codes, conservators could eliminate a potential loss of accuracy introduced by analyzing a cue track by more subjective forms of visual analysis (i.e. looking at and timing a projection), that could be considered as lossy or having a degree of generational separation from the original. Extraction of the original programming could offer the most exact means of documentation of this aspect of the artwork.
Work has been undertaken by software engineer Adrian McCarthy (2002), and his work does indicate a possible way forward. He has demonstrated that it is possible to reverse engineer a slide-show from the (*Mate-trac) synchronization signal only. This was achieved by writing a bespoke piece of software for capturing, analyzing, and decoding data encoded in audio streams. This can facilitate the re-interpretation of a waveform pulse present in the cue track. McCarthy wrote the software to initially decode a .WAV file version of the SMPTE signal into bit and byte streams and then successfully applied this to the Mate-trac. Adrian later refined his software and entitled it Oddio, but it has not been publicly released. This technique, coupled with a key to what each coded signal does, essentially provides an accurate script for any given show using the Mate-trac synchronization signal (McCarthy 2002).
In terms of a dependency on a proprietary system, the risks are diminished if reverse engineering becomes a possibility. This method would remove the necessity of having a fully functional system to play the work, as the work could potentially be remade from the coded instructions from the cue track, provided you have good quality archival master slides to work from. This is an area of research to further develop as a work currently being acquired into the Tate Collection, A Man Called Love (2008, slide, 35 mm, projection, black and white and color, sound, acc. no. X42727) by Tamar Guimaraes (b. 1967), uses Mate-Trac cue tone. This would facilitate the documentation of the cue tone, so that in future the control device could be replaced, while ensuring the artist intent is accurately captured.
Subject to suitable resource allocation, it is desirable to build upon the knowledge gained during this project, to further ensure synchronized slide-based artworks can be displayed without compromise in the future. Further avenues of research may include:
-Expanding the comparison test to include Stumpfl (Wings Platinum) and the Baessgen Triplex+ controller, both of which have backwards compatibility with a variety of cue tracks.
-Refining the means of documenting fade rates by producing slides specifically for this purpose.
-Investigating alternatives for capturing audio control data using digital oscilloscopes and considering potential options for hardware emulation with micro controllers.
-Refining methodology for cue track identification.
-Reaching out to industry professionals with specialist expertise, such as current or former employees of companies that produced slide synchronization (multi-image) control systems, who may be willing to collaborate and advise on preservation techniques.
-Engaging software programmers to develop solutions for reverse engineering slide synchronization cue tracks.
Conservators are presented with many challenges when preserving slide-based artworks, due to both technical obsolescence and the availability of persons with the relevant expertise to work with such equipment. For the synchronized slide-based artworks, this challenge is increased by the need to capture detailed information about the precise timings, and in many cases, this is stored in the cue track. Due to the variety of cue tracks used for the Tate collection works, it is currently necessary to continue supporting two to three control systems. Options for format migration have not been considered as part of this project, but as part of a preservation strategy documenting synchronized slide-based works using video recording is highly recommended, and in future it may be possible to reverse engineer cue tracks to extract the score to these coded sequences.
Many thanks to Patricia Falcao, Louise Lawson, and Anna Nesbit of Tate for all their invaluable help, support and specialist expertise.
In memory of Adrian Fogarty.
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(Former) Senior Conservation Technician, Time-based Media
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