Digital Image Articulator

Tool Identification

Name of tool: Digital Image Articulator
Alternate name: Emulsifier, Vasulka Imaging System, Imager
Inventor/Designer: Woody Vasulka; Jeffy Schier
Date of design: 1976

Historical notice

From the early seventies, videomaker Woody Vasulka began closely following the development in digital technologies while primarily using analog tools (keyers, switches, colorizers) to manipulate the video signal. Around 1976, he acquired an LS-11 microcomputer to begin programming video signals with binary code. Thanks to a grant from the New York State Council on the Arts, he teamed up with physicist Don MacArthur and computer scientist Jeffrey Schier, who helped him build and operate the Digital Image Processor. At this stage, the device was a prototype, but its components would later be recycled within the complex structure of the Digital Image Articulator. Don MacArthur was responsible especially for the infrastructure of the analog digital converters. Videomaker Walter Wright joined the team and devised the first programming schemes. That same year, Jeffrey Schier and Woody Vasulka designed the Digital Image Articulator (also known as the Imager, Vasulka Imaging System and Emulsifier), which improved the interface between the hardware and software components of the Image Processor. Tested by Steina and Woody Vasulka between 1979 and 1987 in many different videotapes, the Digital Image Articulator remained at the prototype stage.

Description of the tool

The Digital Image Articulator consists of analog and digital components on a processing rack as well as a microcomputer.

List of components

Analog to digital converters; buffers; microprocessor; bus; microcomputer; digital to analog converters; oscilloscope.

Operating mode

The Digital Image Articulator is a hybrid device that processes video signals and combines analog functions with digital components for programming. The device breaks the video image down pixel by pixel and reshapes the digital components in an environment governed by mathematical laws. The first step in processing the image is to translate the video signal on an x/y grid. The camera or other signal generators are then linked with analog to digital converters, which transform the inputted analog values into logical values (binary code). The luminance level of the video frame is the measuring unit that generates an image in a digital environment. Its resolution on a grid of 128 x 128 pixels therefore depends on the range of sampling of analog values during video scanning. The higher the number of bits (for a total amount of four), the higher the resolution or the density of the outputted image will be. One bit gives two levels of density (on/off), two bits give four levels, and four bits give 16 levels.

The address generation circuitry on the x/y grid generates the synchronization signal that writes data related to the images in the buffers. These data are then converted into analog signals and reinserted on the monitor via the synchronization generator. At the stage of programming the effects, two digital inputs are juxtaposed. The first, from a camera focusing on the object, goes through the analog to digital converter. The second is abstract and generated in the internal components of the computer (with help from algorithms). With a 256 words software, a sequencer writes addressing commands for the microprocessor through an LS1-11 microcomputer keyboard. These components are also responsible for controlling the order of registers that sequence the data from the buffers. This computer interface includes a rectangular image frame generator and a digital unit for programming, the ALU (Arithmetic Logic Unit) based on Boolean algebra. Boolean algebra, which underlies all computer systems, translates signals into logical utterances. These signals then find their equivalent in variables controlled by the binary code and can link software and hardware. The ALU schematizes the arrangement of the basic components of the Digital Image Articulator logically. When commands are written, the programmed effect shows automatically (in real time) on the screen. For example, thanks to ALU algebraic functions, it is possible to divide the screen into four rectangular zones and program in specific effects. The functions can also be carried out in loops or randomly (the application of logical operations or programmed effects on the video data is followed by a pause where the source image appears in high resolution).

Effects

Pixelization; contrast amplification; compression and expansion of the frame; creation of complex geometric patterns based on algorithmic structures; retroaction of programmed digital effects.

Consulted documents 

[Vasulka, Woody] ; [Schier, Jeffy] ; [Moxon, Tom]. — The articulator manual. — [ca. 1977]. — [81] p. — Unpublished instruction manual of the "Digital Image Articulator". — Computer printout. 

Steina & Woody Vasulka. — Digital images. — Buffalo : WNED Buffalo ; [S.l.] : The Vasulkas, 1978. — DVCAM, colour, stereo sound, 29 min 17 s. 

Vasulka, Steina. — Cantaloup. — New York : Television Laboratory : Thirteen/WNET ; [S.l.] : The Vasulkas, 1980. — DVCAM, black & white, stereo sound, 24 min. 

Vasulka, Woody ; Vasulka, Steina. — Eigenwelt der Apparatewelt : Pioniere der Elektronischen Kunst = Pioneers of electronic art. — Artistic direction by Peter Weibel, edited by David Dunn. — Santa Fe : The Vasulkas ; Linz : Ars Electronica Center, 1992. — 240 p.