centre for animation & interactive media

Animation Tech Notes #1
Of Peg Bars and Field Charts -
Tools of the Trade
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REGISTRATION SYSTEMS

One of the first problems animators faced when drawing on hundreds of sheets of paper, was the accurate alignment of each drawing on every sheet so that the artwork did not jiggle about when photographed and projected. There are a number of ways in which these sheets of paper can be aligned.

SIMPLE SOLUTIONS

Pencil registration marks in the form of two small crosses the same distance apart can be made on the opposite sides of every sheet the paper in the sequence. Each drawing can then registered by hand. This is not a particularly practical method of production when shooting many drawings but is very useful, for example, to register the head of a character drawn on a scrap of paper so that it can be traced off onto its body which may be bouncing up and down. Such registration marks can also be useful for accurately positioning parts of a character within a computer graphics system.

Another simple registration device is an 'L' shaped stop of thick cardboard which can be stuck down onto a drawing board. The corner of each sheet of paper is then pushed into the 90-degree angle of this 'L' with the base of the paper resting on its long side.

A two hole office punch used for punching paper to insert into loose leaf binders can make an inexpensive and effective registration system. Pegs can be made from two 1/4 inch dowel posts inserted into a piece of board.

PROFESSIONAL REGISTRATION SYSTEMS

An investment in a professional registration system made specifically for animation where precise registration is required, is by far the best solution. While these professional systems are expensive, they are also very accurate and allow your animation to be photographed on an industry standard animation camera, or scanned into a computer with accurate registration.

There are two major standards in use world wide. The 'OXBERRY' system, named after the firm that manufactures much of the professional calibre animation rostrum cameras used around the world, and the 'ACME' system.

Both systems use a single central 1/4 inch peg with two rectangular bars either side some 4 inches out from the centre. The OXBERRY system has bars which are 1/4 inch wide, while the ACME system has 1/8 inch wide bars. It is the ACME standard peg bar system that is the most widely used in Australia.

The rectangular slots punched into the cels or paper on each side of the round peg, are usually wider than the rectangular pegs onto which they fit. This allows for the expansion and contraction of the cels once they are exposed to the hot lights of the camera room and prevents the buckling of cels which can be a problem when using a two-hole office punch system.

These professional registration peg- bars are also widely used in industry for keeping strict registration when digitising artwork into computers using either a flat-bed scanner or video camera.

A set of plastic pegs cost about $3 each, while a flat metal bar with a set of mounted metal pegs cost around $25. An animation disk with full bells and whistles, sliding top and bottom pegs, can cost between $250 - $800!! The complete range of tools for the animator is available from 'The Cartoon Color Company' of California USA.

Paper has to be specially punched. The punch itself is a very expensive item costing up to $1200. Don't let this deter you from using this professional registration system, however, as most local animation studios will happily let you use their punch if you supply the paper. Past students often visit us for this reason too.


ANIMATION FIELD SIZE

The area of a picture that is framed by the camera when a scene is being shot is known as the 'field size'. The field size can be anything the animator chooses, but is usually kept within the standard sized fields of either 12 or 16. A 12-field measures 12 inches from the extreme left side to the extreme right side of the artwork, with a height of approximately 8 and 3/4 inches from top to bottom.

Field sizes can be as variable as the technical versatility of camera used for shooting the artwork. Usually a rostrum camera can focus in as close as 2 inches wide, or can pull back to a 24-inch span, or more in some cases.


ASPECT RATIO

Regardless of field size, the dimensions of the frame must always assume a ratio of roughly 3:4, height to width (1 to 1.376 in actual fact) as used in super 8mm, 16mm and 35mm film formats, except for CinemaScope and other 'wide-screen' configurations. This aspect ratio is called the standard Academy field ratio. Television also uses this ratio for its screen dimensions.

Television 3:4
Digital Video (DV) 3:4 - (720 x 576 pixels)
Standard Academy (35mm film) 1:1.33
Standard wide screen 1:1.85
High Definition Television (HDTV) 16:9 - (1920 x 1080 pixels)

FIELD SIZE GRID

Camera operators, layout artists, directors, and animators all keep track of field sizes with a field guide. This is a transparent sheet with a series concentric rectangles at increments of one-inch in width conforming to the standard Academy screen ratio. Also indicated on this grid are four directional reference points; North, South East and West.

Camera field sizes are given in common animation parlance with a simple number. An 8 field, for example, is exactly 8 inches wide. A 5.75 field measures 5 and 3/4 inches in width. The function of the field guide is to provide a standard co-ordinate system so as to specify the area that the camera will be set up to photograph. It is also a vital aid to the animator in laying out a scene, working out the final composition of shots and in specifying any camera moves. This means that if you have your paper and cels photographed on a professional stand, (or scanned into a computer) the camera operator will always be able to line up your artwork in exactly the same way as you designed it.

A standard 12 inch field guide. The bolded rectangle indicates a field size of 4 offset at 1.5 West and 1 North. This may indicate a compositional area at which to start a scene.

 

 

 


FIELD GUIDE/CAMERA RELATIONSHIPS

There is a direct relationship between the field guide and peg bars used to register the animator's drawings and the animation camera itself. The centre of the field guide is matched to the centre of the cameraÕs frame. All directions for movement from the central position can be indicated by a numeric value in either the N (North), S (South), E (East), or W (West) quadrants. This allows animators to specify precisely and universally the position of any point under the camera.

Field sizes allow the director and the animator considerable flexibility. If the director wants the camera to move in on a close-up of an object in the frame, the camera operator can be instructed to go from a 12-field to a 7-field. This will give the effect of a truck into a close-up more easily than drawing the movement in perspective could. This standardised system of coordinates permits an animator to provide very exact instructions for complicated camera movements. The following instructions would be immediately understood by any animation camera operator: start position: 8 field 0:0, end position: 4 field, 2 N / 3.75 E. Track and zoom in over 40 frames.


An animator also may prefer to draw a character within a certain area because the pencil strokes are more comfortable for the hand and wrist, so the drawings are done on a 6-field instead of a 12-field area. That's okay because the camera or scanner can be made to cover only that area so that the characters will fill the entire frame as completely as if they had been drawn bigger on a larger field.


AIM STUDIO STANDARD

Because AIM has been producing animated films using A4 sized flat-bed scanners for well over a decade, we have developed our own field guide standard to suit A4 sheets of paper. The AIM field chart is 9 field, i.e. 9 inches across by about 6 and 3/4 inches high. The centre cordinates are also slightly lower than the industry standard field guide. It is just possible to squeeze a 10 field area from the AIM system before the pegs begin to show up in your scan.

TV SAFE AREA

When a film is broadcast over television, part of the picture area is always lost. Today, most animation is produced for television, so strict attention must be paid to TV cut-off and TV safe-titling areas when planning a scene.

Television cut-off is the area within the field size where the viewer's TV screen crops in from the edge of the shot, thereby concealing a certain amount of the scene. The cut-off varies from set to set, and from region to region, and therefore can never be accurately predicted. A maximum loss of 20-25% cropped off from all sides is a good safe guide.

All important action should take place within this safe area. It is heartbreaking to see your precious animation which occurs too near the edge of screen and elements of your beautiful backgrounds, chopped off or entirely missing because of an oversight in design and composition.


It was Raoul Barre who first devised the system of punching the paper and placing pegs on the animators' tables, the inkers' desks, and the camera stand some 75 years ago; a system still in use today. These animators' tools of trade mean that layouts designed in New York, backgrounds painted in California, animation created in Australia and cels inked and painted in China, can all be brought together in perfect registration under a camera in the Philippines and shot just as required... er, in theory at least.
Thanks Raoul!


Read on....


"You mean if it
wasn't for pegs bars
I'd be jiggling around
all over the place?"

When designing work for either cinema or television distribution, its vital that you consider the amount of screen area around the edges of your layout compositions that is likely to get cut-off. Essential visual storytelling information should occur within about 15% of the outside edge of the screen and titles and credits, within 25%.

Sources and Other References:

See also: Dope sheets or Exposure sheets

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