THE SECRET OF NIMH is an animated feature from Don Bluth Productions which represents an attempt to resurrect classic animation techniques and combine them with newer techniques not commonly used on animated features. The emphasis throughout is on the use of every available method to increase the illusion of reality and to engage the viewer in the story. Bluth did not want any of the effects to stand out on their own, but he was determined to invest the maximum possible time and effort into the rendering of every scene in order to enhance the story. Techniques used on THE SECRET OF NIMH which have not been used extensively in recent animted features include split exposures to create shadows and translucency, diffusion in conjunction with split exposures to create reflections, color Xerography for the creation of cels and painstaking color orchestration.
Newer techniques include the use of video animation for testing and backlight. The use of multiple exposure techniques is probably the best indication of the time and effort taken with the film. The average number of passes through the cameras for a scene in the film was probably four (in comparison with a more common average of two on other contemporary animated features) and some scenes required as many as twelve passes. Similar efforts were made in every phase of production.
Don Bluth Productions began as a group of Disney animators working nights and weekends in Bluth's garage developing a half-hour animated film called BANJO THE WOODPILE CAT seen in May on ABC-TV. Eventually the group left Disney, expanded and moved into office space in Studio City. The first camera used for shooting tests was a relatively simple Fax stand of the sort a television station or film school might use, and one of the first steps in the production of THE SECRET OF NIMH was the design and manufacturing of two custom animation stands. Six months were devoted to developing the design specifications for the cameras, and then another fourteen months were spent building and testing the camermas. Two identical camera stands were built by Mechanical Concepts especially for Bluth because there were no animation cameras available commercially that could do everything necessary to shoot THE SECRET OF NIMH, according to Fred Craig, Director of Special Processes for the film.
The main requirements which coud not be met by existing cameras were the capability of multiplane photography and a rotating camera head. Some animation stands include a rotating bed which can accomplish the same effect as a rotating camera head (i.e. making an image spin around), but working with a rotating bed is a great deal more awkward since the operator must follow the bed around as it rotates. There were no cameras capable of doing multiplane work anywhere outside of Disney studios. While the camera designed for Bluth is not as large and complex as the multiplane at Disney, it is capable of shooting on two planes and is operated electronically instead of manually.
The camera has an electronically controlled follow focus engineered by Elicon which can be selectively set to follow either plane as the camera moves or to shift gradually from one plane to the other (i.e. it can do a focus pull during a shot). The point of a multiplane camera is that it can create an illusion of depth by combining a foreground and a background, one of which is slighty out of focus. The two planes can also be moved independently of each other to enhance the sense of perspective.
The camera also has an electronically controlled shutter for doing fades and dissolves. It can be set to any length between 5 and 999 frames, and it has different curves for doing fades and for doing dissolves. The nature of a dissolve curve is such that it maintains a matching density on each element and is calibrated slightly differently than the gradations on a stright fade-in or fade-out.
The rest of the controls on the camera are not electronic, but the camera was designed so that it can be hooked up to a computer. Stepped motors are used that can be controlled by a computer, and the camera will probaby be completely conputerized before the next production. The main benefit of conputerization is the repeatability of a shot and the reduction of the margin for error in doing multiple passes. It makes the operation of the camera slightly faster, but it does not eliminate the most time consuming spect of animation photography which is the handling of the cels.
One feature on the camera which does help reduce the time required to lay down the cels, however, is the automatic platen which is activated by foot pedal. Another feature is the use of polarized light since dust or fingerprints on cels do not show up so much with polarized light and less time has to be spent cleaning the cels. Even though polarized light is more or less standard with commercial animation camera services, many of the artists at Bluth were opposed to the technique at the outset. Polarized light was not used at Disney because of the green color shift it can cause. Tests at Bluth Studios convinced everyone that any color shift caused by polarized light could be corrected in the timing at the lab. It did take a while to adapt to the use of polarized light, however, because it can cause a blocking up in darker areas of a background. Wedge tests on the initial backgrounds enabled the background artists to see how the film responded to their work and they were able to adapt their treatment of shadow areas accordingly.
Another feature which the cameras built for Bluth have that is not found on conventional animation stands is the capability of shooting backlit art in an anamorphic format. Although THE SECRET OF NIMH was not shot in an anamorphic format, the next production probably will be; and this was an essential element in the camera design.
The first step in the production after the scripting was the storyboarding. Full color renderings were used for about a third of the film, but time pressures resulted in the use of black-and-white boards were done in a gray wash rather than a simple line drawing.
A first rough version of the entire film was constructed by shooting the storyboards in continuity and synching them up with the dialogue track. Adjustments were made in the timing for each scene in the storyboard stage until it was felt that the continuity was sufficiently locked down.
The next step in the production was pose tests done by the animators for each characer in a scene. A pose test would consist of a position for every eighth frame. These pose tests would be evaluated with the help of a video animation stand and then a rough test would be done with a line drawing of every other frame of motion. These tests would be further refined using the video animation until the sequence was ready for all of the in-between artwork and a film test would be shot of the pencil drawings on paper.
The video animation was done by means of three Lyon Lamb 1/2" reel-to-reel video recorders modified to record one frame at a time while advancing the tape very slowly. The recorder does not have to back up and re-cue to get a running start each time a frame is recorded. The animator positions his artwork on a platen, adjusts the framing of the video camera by means of its zoom lens while referring to a small monitor, and then presses a button on the tape deck. The recorder will beep when the frame is recorded and he proceeds with the next frame. The entire setup is compact enough to fit on a table top, and simple enough to use that each animator could shoot his own tests of whatever he was working on. It would take perhaps fifteen minutes to shoot a test for a ten second piece, and the results would be available immediately to view and evaluate. Needless to say, this made for a degree of testing that would never have been possible within the same amount of time if the tests has been shot on film. Even with in-house processing it probably would have taken at least five times as long to make a test on film.
In order to create the most realistic possible motion for some of the objects in the film (as opposed to the characers) high-speed photography of models was used. A model would be shot at 96 frames per second in order to get the maximum possible sharpness for the movement and then every fourth frame would be printed optically and rotoscoped to provide the basis for the art. This was used with great success for the boat, the lantern elevator and the bird cage. An attempt was made to use a model of the tractor, but the model proved to be too small; and it was not possible to get an adequate depth of field in photographing it.
Live action film was also used as a reference in animating the movements of the human characters. There as no actual rotoscoping of human movements but footage was shot and analyzed on a viewer.
Once the pencil drawings were completed, a film test was shot so that the animation could be viewed in sync with the track. The video tests had no sound track with them although a crude comparison could be made by playing the track separately. If the film pencil test was satisfactory, work would begin in preparation for transferring the art to the cels. There were 25 or 30 people working on the pencil drawings, cleaning them up and turning them into a very fine pencil line drawing which would then be Xeroxed onto the cel. The care taken in cleaning up and refining the pencil drawings in order to get the finest possible line on the cel is another example of the attempt to duplicate the quality of classic animation with contemporary techniques. In the old days the lines would be inked onto the cels by hand in the appropriate color, but this approach is no longer economically feasible. The ability to Xerox lines onto cels was a major breakthrough in animation technique in 1958, but it can result in relatively crude line drawings if great care is not taken in refining the pencil drawings prior to Xeroxing.
Another way in which Bluth has attempted to emulate the classic animation technique is through the use of color toners in the Xerox process. Rather than simply Xerox all the lines onto the cels as black lines, fourteen different colors of toner were used to create the same effect as was achieved by inking the cels with colored ink. Color Xerography is not a new technique, but it has fallen into disuse, and it was necessary to have the color toners formulated especially for THE SECRET OF NIMH. There were four shades of gray and ten hues in addition to the normal black toner used in making the cels. Using a complementary color to define an outline rather than black helps to reduce the viewer's sense of the flatness of the image and increase the sense of reality. For example, flames in a fire are much more convincing if they are outlined in red or yellow than they would be if outlined in black. Similarly, Xeroxing the outline of Jeremy the Crow in a light gray made it much easier to delineate him since a black line would not read against the black paint for his body. In some instances the cel would be touched up in order to use more than one color line on a single cel. For example, Jeremy the Crow was Xeroxed in a light gray, but it was necessary to darken the outline for his yellow bill and feet if the lines were to read properly. This was done by rubbing the lines with pastel in the appropriate area. Occasionally when a line needed to be colored rather than just darkened, it would actually be redone with ink as in the case of a character's eye.
The color to be used in Xeroxing the pencil drawings was determined in conjunction with all the colors for a scene or character. The degree of attention given to color orchestration for THE SECRET OF NIMH is yet another example of the quality of the production work done on the film. There are more than 600 colors used in THE SECRET OF NIMH. One character, chemist mouse Mr. Ages, has 26 colors. There were daily meetings of the key staff members to discuss the color choices. Ten or twelve "color models" would be done for a character (i.e. renderings with different color combinations and values) in order to choose the best color scheme. The backgrounds were pained mostly with designer gouache (a re-wettable water color that can be re-worked) and wedge tests were shot for all the backgrounds. The color scheme for a scene was chosen to augment the emotional content of the scene and would vary as the scene progressed through different emotional beats. The best example of this is probably the scene in which Mrs. Brisby and the Shrew try to stop the tractor. It is set at daybreak so that the colors of the background can progress from gray to oranges and reds and then to blues and greens as the emotional content of the scene intensifies and then relaxes.
There are 1078 backgrounds in the film, all of which were tested and then shot in continuity to time so that the entire films could be viewed with the track in the film of just the color backgrounds. This enabled the overall impact of the color scheme to be evaluated and some backgrounds were repainted as a result.
Once the color scheme for a sequence was set, the pencil drawings were Xeroexed on the front of the cels and the cels were then painted on the back side. They were then turned over to the camera department.
By the time a sequence was shot "for real" it had probably been shot in some preliminary form five or six times. If the sequence involved a backlit effect, it was always wedged to determine the best exposure for the effect. At the outset everything was wedged, but as the production progressed it was decided to wedge only the backgrounds and the backlit effects. The photography for the film was done from August through May with a night shift doing the pencil tests and the day shift doing the color. There were over 1000 scenes and only a few dozen had to be re-shot because of some discrepancy in the multiple exposure. An example of a scene that required twelve passes is a shot in a lab which included a background, two characters, their shadows, a Bunsen burner flame, a rope and bubbles rising to the surface of a liquid. Shadows were created by a split exposure using an opaque matte for the shadow area on one exposure. Glowing effects and reflections on a shiny surface were created by superimposing a backlit or a diffused image in a separate pass.
In perhaps twelve instances scenes were composited on the optical printer when it was not possible to do all the work on the animation stand. These were generally scenes involving movement on the axis perpendicular to the film plane. For instance the scene in which the rats fall through the vortex was composited optically. The backgrounds were painted about twice the size of other backgrounds and the camera shot a linear truck into the background (i.e. the move did not appear to slow down but seemed as though it would go on forever). The rats were then matted into the moving background optically using mattes shot on the animation stand.
In the course of producing THE SECRET OF NIMH Bluth and his coproducers Gary Goldman and John Pomeroy conducted in-house training sessions in classical animation techniques for new staff members. These sessions were videotaped and may eventually be turned into an educational tool for distribution to schools and libraries. Bluth likes to think of THE SECRET OF NIMH as a film which is ushering in The Second Age of Animation, and he hopes that his studio will be a major factor in the revitalization of the art of animation.