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\F0\CComputer-Assisted Etching
\CEdith Smith


\J
     In my experiments with computer-assisted etchings over 
the past eight years I have tried to harness the graphic 
potential of available computers to the traditional art of 
fine printing, without sacrificing the refined beauty of 
gravure on rag paper. I have tried to integrate computer 
functions with the functions of engraving, aquatint, 
monotype, and other hand techniques in enhancement of a 
complex, figurative, lyrical style.  The completed prints 
display little of the geometry usually associated with 
"computer graphics."  Employing principles of 
metamorphosis, I have used the computer for codification, 
development, transformation, and composition of visual 
images.
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\J
   With the technology available to me -- a Digital 
Equipment Corporation PDP10 computer with display, later a 
"home computer," the Radio Shack TRS80 micro-computer and 
dot matrix Microline 80 printer, a Calcomp plotter, a 
Varian electrostatic printer, a thermofax machine, a copy 
camera and darkroom, Revere photo-sensitive etching plates 
and chemicals, and an etching studio with press -- I am 
able to process ideas through several steps into fine 
intaglio prints.
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\J
   I rely on graphics programs of three types: edge 
finder programs; dot matrix programs for letter type; and 
drawing programs.  In the first two kinds of programs a 
video camera directed by a PDP10 computer shoots art work, 
objects, or type fonts.  The value information of the video 
input is digitized and processed to a linear codification 
suitable for etched line.  The edge finder program finds 
edges of real or illusional objects and sorts out levels of 
contrast.  It establishes thresholds for value change.  
Demarcation of maximum value change creates a firm line.  
Less value change creates broken lines.  Minimum value 
change creates dots.  The thresholds for value change 
"readings" can be moved easily.
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\J
   The drawing program is a general purpose computer 
graphics package.  It is used to create libraries of 
pictures which may be called on by other programs or output 
on any kind of hard copy system.  It permits editing by the 
insertion and deletion of points, by the movement of 
points, or by the combination of drawings or fragments of 
drawings.  An x-y coordinate system is established.  The 
x-y information may be entered into the computer memory 
from a typewriter keyboard, or from files produced by 
mathematical formulas, T.V. pictures, or by light pen 
activity.  The output of the programs is stored as hundreds 
of short line segments which may be produced as line 
drawings by the computer-operated plotter or electrostatic 
printer.
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\J
   Since visual data is expressed in numbers, distortions 
of the image can be effected by applying different factors 
to the numbers.  To modify an image, I set it up on a 
vertical-horizontal axis, establishing x as a horizontal 
coordinate and y as a vertical coordinate.  Every line is 
made up of hundreds of points, each having a vertical and 
horizontal number coordinate.  Once these coordinates are 
given, they can be shifted by multiplication, division, 
addition or subtraction.  The image can undergo gradual 
metamorphosis; it can be curved, turned inside out, 
compressed to one point and then reversed, fattened, 
thinned, elongated.  Positive or negative function may be 
used.
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\J
   To illustrate, the diagram in figure 1 presents two 
images, a jagged line and a smooth curve.  Each is broken 
up into 1024 separate points which can be considered to be 
between zero and one above the horizontal axis.  When the 
corresponding numbers from each shape are multiplied they 
produce the third shape.  The beginning and end points of 
the jagged lines are at zero.  No matter what zero is 
multiplied by the result is always zero.  When the top 
point of the first peak is multiplied by the corresponding 
peak of the curve the resultant image is expressed as 1 X 
.2, or .2.  The curve of image three and its peaks touch 
the original curve.  In the lower set of shapes the curve 
moves into the negative realm.  When the curve reaches its 
lowest point the level is equal to -1.  So, if the first 
shape reaches a high point in the same position, the result 
is -1 X 1 = -1.  Again, the curve may be exactly 
superimposed on the result of the multiplication.
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\J
   My computer-assisted etchings contain original poems, 
etched into the plate and integrated by design with the 
formal elements.  The computer type fonts are usually 
created as dot matrix patterns.  The line printer can 
create such letters on a field of approximately 7X9 dots.  
The rough copy this produces is adequate for casual use but 
to approach the printing quality of conventional type 
setting systems as many as 30X40 dots per character are 
required, with dots spaced at 1/200 inch intervals.  This 
dot spacing is achieved with the computer-directed Varian 
printer.  I have a choice of forty type fonts in a wide 
range of point sizes.  In the "Ancient Cities" series I use 
Bodoni Italic and Bodoni Extended, 10 point and 12 point 
sizes.  In the positive film copy these letter lines are 
black.  They are exposed as positive lines on the zinc 
plate.  After development, they are bitten in the same 
manner as a needled line.
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\J
   Editing, further instructions, and layout are handled 
at the computer display screen.  Opaque copy is produced by 
the printer or plotter.  (Figure 2.)  This copy must be 
made transparent either by copy camera or, in more current 
practice, by one of the plain paper copiers (Xerox, 
Minolta, IBM) or by 3M Thermofax.  In recent years I have 
bypassed the expensive Kodalith graphic arts film and I 
have worked directly from acetate copy produced by one of 
these machines, making a "paste-up" film for exposure onto 
a photo-sensitive etching plate.  The plate is exposed, 
using a carbon arc lamp and a vacuum table.  The plate is 
then developed with Revere photo chemicals.  From this time 
forward any traditional etching technique may be employed.  
The photo-resist may be chemically removed in part, 
exposing large areas of the plate to aquatint or marblized 
aquatint in the nitric acid bath, or baths, which follow.  
I often make a second registered color plate, using soft 
ground or painted monotype to add luminosity to the 
somewhat mechanical looking computerized plate.  After 
hand-working and etching, the plate is ready to be inked 
and printed on an etching press.  Accurate plate 
registration is accomplished by inking all plates before 
the press run, by trapping the rag paper under the press 
cylinder, and by printing subsequent plates immediately, 
before the dampened paper dries.  (Figure 3.)
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\J
   My most recent computer-assisted etchings, the 
four-print series "Ancient Cities," combine a poem with 
digitized images from Yucatan and Paris.  The etchings are 
based upon spontaneous on-location drawings of these 
locales.  From existing structures I have chosen several 
compelling architectural forms, expressive of an age:  
these forms not only house man but they survive him and his 
societal pageantry. In "Ancient Cities IV," here pictured 
in its entirety, figure 4, the images are derived from El 
Caracol, the Observatory, Chichen Itza, and from the Centre 
Pompidou, Paris, with its unique escalator and exposed 
pipelines.  By the juxtaposition of a bird in flight, the 
Mayan architecture (reduced to minimal pattern), and the 
modern architecture of the Centre Pompidou (also 
minimalized for barest recognition) I have hoped to provide 
a foil for my word-play about how TIME, as we measure it, 
is a tool of the ego; without the intrusion of the ego it 
could be seen as a non-linear dimension.  The close of my 
poem suggests these sentiments:
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       "As Modern Cities jive, with their callous blasts,
           and their acrid smells,
           their jangling wires:
           Are they, too, ghost to some
           millenium?"
\J
     The gradual transformations on the computerized plate, 
figure 5, exemplify computer distortions of the Centre 
Pompidou, with escalator and bird.  Here three waves are 
superimposed upon a single arc and multiplied up to sixteen 
times.  The severe wavy distortion is unrecognizeable 
except when seen in serial context.  There the delight for 
the viewer lies in a constant reinterpretation of form.  A 
detail of the completed print, figure 6, shows textural 
bitings on both etching plates (soft ground, drypoint, and 
marblized aquatint) and monotype painting on the registered 
color plate.  The architectural forms appearing and 
reappearing, altered by film overlays and an infinite range 
of computerized changes of scale, provide a counterpoint of 
elements which evoke for me a sense of the simultaneity of 
past and present.  Computer processes blend imperceptibly 
with more traditional technologies.  Indeed, the computer 
has become for me another graphic tool among many, to be 
employed with conventional printmaking techniques in the 
production of etching.
     Computer graphics in film and video have become common 
practice in technologically advanced communities.  The 
application of the computer to other visual arts is surely 
just beginning.  In the future, as hardware becomes more 
reasonably priced, artists may write programs for special 
needs in painting, sculpture, and the applied arts.  My 
computerized printmaking taps only a small part of such 
potential.
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