The fi rst canon in the making of instructional fi lms is to avoid any confusion in the mind of the spectator about the relation of each shot to what precedes and follows. Something easily recognisable in each shot must carry the eye forward to the next. This means in practice that every change of view (i.e., every cut) should be motivated by a deliberate action or camera movement. Failing all else, the pointing fi nger may have to be used before a cut to provide a suitable movement carrying the attention forward. Normally, however, a natural piece of action — an upward glance from a character, for instance, taking us naturally with a cut to a shot of an aeroplane — is preferable, because it makes the change of view more inevitable. Alternatively, the same effect may be achieved by panning or tracking the camera until a piece of mechanism singled out for attention is in the centre of the frame; after this, cutting to a close shot of the mechanism makes a logical piece of continuity while establishing beforehand the geographical position of the detail in relation to the whole.
In working with diagrams or models, these conventions are still valid — a principle often ignored by animators.
Diagrams should, as a rule, not be used unless there is no other way of explaining a point with equal clarity. When diagrams are used, it is most important to make exactly clear what they refer to, and which portion of the previous picture they are showing in detail. This is accomplished most simply by the matched dissolve, but numerous other simple continuity devices are possible. Models are used in the same way; they are particularly useful in the exposi-tion of the inside workings of machinery which can normally not be photographed. Many instrucexposi-tional fi lms have used the device of introducing a sectional model of a piece of equipment at the appropriate stage in the argument (by matching its position on the screen with the position of the actual apparatus in the previous shot), and then dis-mantling the sectional model piece by piece. The camera is not moved so that bit by bit the “ works ” of the model are made visible, while the relation of each part to the whole is kept clear. This is only a simple example, but it shows the kind of continuity which must be aimed at when complete clarity of exposition is desired.
To illustrate how an instructional fi lm can be made visually clear by using the continuity devices which we have briefl y noted above, let us look at a sequence from a fi lm which uses no commentary but attempts to clarify an intricate process in pictures alone.
CASTING IN STEEL AT WILSON’S FORGE 1 Extract from Reel 2
Part I (Making a Mould) shows the various processes concerned in preparing moulds for mine-tub wheels. It ends showing a line of moulds ready for the molten steel. Part II, quoted here, shows the preparation of the steel, and Part III (Pouring and Finishing) shows how the molten steel is poured into the previously prepared moulds.
The fi lm is silent throughout.
TITLE: Part II: Melting and Converting
Fade in
Ft.
1 Exterior Foundry. M.S. Base of Cupola. Ladle on crane-hook standing under spout of cupola. One of the furnacemen is unplugging the tap-hole with an iron tapping bar.
24
1Director and Editor: R. K. Neilson Baxter. Basic Film Unit for Ministry of Education, 1947.
“ Casting in Steel at Wilson’s Forge”
Ft . 2 C.S. Spout. Shooting across top of ladle. Furnaceman moves away. A
long-handled “ pricker ” is pushed in from out of picture and fi nishes unplugging the tap-hole. Molten iron runs down into the ladle.
23
3 M.S. Base of Cupola. As in 1. The molten metal running into the ladle. A “ tap-hole rammer ” comes into picture and is rested on the cross-bar of the ladle. It has a plug of clay pressed on to the end.
9
4 C.S . Spout. As in 2. The ladle is now nearly full of molten metal. The rammer is pushed in and twisted until the fl ow of metal stops.
12
5 M.S. Base of Cupola. As in 3. The rammer is withdrawn and the furnaceman comes into picture. He skims off the slag from the top of the ladle. His mate comes in past camera and takes up his position at one side of the ladle.
20
8 F.S. Bessemer Converter, from behind ladle. The converter is in its horizontal position. Ladle is lifted (by the crane, out of picture) and swung across to the mouth of the converter. The furnaceman and his mate go up on rostrums at either side and the ladle is passed up to them. Furnaceman starts to turn control-wheel.
30
9 M.S. side angle, Bessemer Converter. Furnaceman turns control-wheel and contents of ladle pour into converter.
36
10 F.S. Bessemer Converter. As in 8. Contents of ladle fi nish pouring into converter and it is swung away upside down. Furnaceman and mate come down from their ros-trum and wheel them out.
12 Diagram. F.S. Bessemer Converter. Approximately as in previous scene. After a few feet, exterior of converter dissolves away so that it appears in cross-section. This shows the air entering from the duct at the side and passing up through the tuyeres into the molten metal. Fumes and fl ames rise from the surface of the metal.
18
13 Diagram. C.S. Air Duct. To establish the word “ Air. ” 10 14 Diagram. F.S. Bessemer Converter. As in 11. Animation as before. Fade out. 16
Fade in.
15 Exterior Foundry. M.S. Chemist, looking up out of picture. Camera pans to top of converter. A long fl ame is shooting up from the top of it.
16
18 F.S. Bessemer Converter, looking into the mouth of it, stationary, in the horizontal position. Blowing has ceased.
8
Ft.
19 L.S. high angle, Bessemer Converter. Two foundrymen move in with small ladle.
They place ladle on rails below converter mouth. Converter tilts slightly and metal pours from it into ladle. The furnaceman pushes back any slag in the lip of the con-verter mouth to let the metal pour easily, and the foundrymen move away to avoid the splashes. When the ladle is full, the converter tips up again, the two foundrymen move back and a third one puts an anti-glare cover on top of the ladle.
31
20 M.S. Bessemer Converter. As in 18. Third foundryman placing cover on ladle. He places a cross-bar under the left-hand end of the carrying bar and the three men lift the ladle and carry it into the foundry.
18
Fade out.
The fi rst shot establishes the position of the apparatus. The camera is placed to show the exact position of the cupola-spout (down which the metal will fl ow) relative to the ladle (which will receive the metal). We see in the background that a furnaceman is doing something to the tap-hole of the cupola; this leads to the second shot where the tap-hole is shown from the front. The two shots are clearly linked because we see the same pieces of apparatus and the same furnaceman. The head-on view of the cupola-spout ( 2 ) shows that the long tap-hole rammer is in fact opening the tap-hole and causes the steel to pour into the ladle.
In actual practice, it takes some considerable time for the ladle to fi ll up with molten metal but there is obvi-ously no point in showing the whole process here. The camera set up in 3 makes it impossible for us to see how full the ladle is, so that when we cut back to 4 we are readily prepared to believe that the ladle is now full, although we have seen in a few seconds a process which might take several minutes.
The position of the rammer acts as a visual link between 4 and 5 and we now see ( 5 ) that the furnaceman is skimming something off the top of the molten metal.
His action is continued in 6 where the camera movement emphasises how the slag is “ killed. ”
The camera pans back to the furnaceman and his action is taken up in 7 which indicates that the process is now over.
Shot 8 is the beginning of the second manipulation of pouring the iron from the ladle into the converter. The camera is set at a slight side angle to show exactly how the ladle and converter are placed relative to each other.
The crane which carries the ladle is not considered of any particular importance and is left out of the picture.
Shot 9 continues the turning movement started in the previous shot; here the camera set-up again ensures that we see clearly what is happening; 10 continues the action to show how the ladle is removed.
We are now left with the converter in the centre of the frame (end of shot 10 ) and we cut to 11 , enabling us to get a better view of the turning movement.
At this stage it is necessary to show what goes on inside the converter and this must be shown by diagram.
A matched dissolve introduces this so that there can be no doubt about what it refers to. The diagram then changes to a sectional view, and since it is important to establish the fact that air is being driven through the converter, a close view of the inlet pipe ( 13 ) is shown.
The diagram sequence is shown at some length because the process of converting goes on for a considerable time. Similarly, the fade which follows makes it clear that there is a passage of time between 14 and 15 . The camera movement in 15 shows that the chemist is looking at the top of the converter.
In 16 , we see by his gesture that he judges the process to have fi nished, and the men begin to turn the winch.
The effect of their turning appears in the next shot ( 17 ) and in 18 the head-on view of the converter estab-lishes that the blowing has fi nally ceased.
The pouring of the metal is now viewed from a new camera set-up to reveal the action to best advantage ( 19 ), and the movement of placing the cover over the small ladle is continued in 20 to take us smoothly to the last shot.
This rather tedious detailed description of the editing of a complete passage has been given here in order to show how every cut is motivated by a deliberate piece of action or a camera movement. Complete clarifi ca-tion of each step is the primary necessity of an instrucca-tional fi lm and it has seemed pertinent to analyse a sequence in detail to show how it is done. In addition, it is worth noting that the director has been at great pains to use as few camera set-ups as possible in order not to complicate the issue; the fi rst seven shots, for instance, are edited from shots taken from only three set-ups.
This excerpt from Casting in Steel at Wilson’s Forge presents the problem of instructional fi lm-making at its sim-plest. The fi lm was intended for a general audience and there was no need to show the processes in any great detail. The subject is, moreover, fairly simple, and could be presented by following the order of operations adopted in practice. Not all subjects are as simple as this. Many points of detail may have to be shown repeat-edly from different viewpoints in order to make them perfectly clear and in such cases a commentary will be essential to let the audience know exactly which stage of operations they are asked to view more than once.
A commentary is, of course, extremely valuable in any event. A hint from the commentator can draw the specta-tor’s attention straight to the point and can keep the fl ow of thought in the desired channel. But it should never be used to convey something the visuals can convey better or to cover up mistakes in the shooting. As any instruc-tor will testify, a practical demonstration is more convincing than complex verbal explanation. With instructional fi lms a simple, lucid fl ow of visuals, such as we have described above, must always be the primary aim.
The techniques employed in the making of teaching fi lms are much more numerous. The nature of the sub-jects and the audiences for which the fi lms are designed are so varied as to make a uniform approach impos-sible. What, however, in general distinguishes the editing problems of teaching and instructional fi lms is the nature of the fi lm continuity. In teaching fi lms the continuity can no longer arise out of a continuity of action, but out of a continuity and development of ideas. It may, for instance, be desirable to illustrate a general prin-ciple by a series of physically unconnected examples. In a case of this sort, there can be little visual continuity from shot to shot and the normal considerations of continuous action editing will become irrelevant. The edi-tor can do no more than produce the least objectionable visual continuity and time the commentary in such a way as to make the cutting appear smooth. But the problem is not as great as it sounds, because, if the ideas follow each other in a logical progression, the development of the argument will draw attention away from any slight imperfections in the mechanical continuity of the images.
If the script has been thoroughly worked out before shooting, and the director has shot the material intelli-gently, the editor’s task is the comparatively simple one of timing the shots. On some occasions, the editor may suggest simple alterations to the intended continuity — if, for instance, shots which were to follow each other are discordant in tone, or the action of one shot directs the eye away from the point of interest in the next; more frequently, it may happen that an unexpected visual inference is created by a particular shot juxtaposition and it may then become capable of a wrong interpretation. (An effect akin to this was demonstrated on one occa-sion while showing Hydraulics to a school class. One of the fi rst questions asked after the showing was, “ What keeps an aeroplane in the air? ” The introduction of a shot of aircraft in fl ight, to make a point in the argument, had somehow turned several of the viewers ’ attention away from the hydraulics principle on to something with which the fi lm was not concerned.) Obviously, in a case of this kind, the editing must be reconsidered.
Although it is true that the motion picture can be used to relate a set of normally unrelated phenomena to illustrate a central theme, the greatest care must be taken in the editing not to let any one of the single phe-nomena become so important as to take away the attention from the whole principle.
Since the ideas presented in teaching fi lms are often extremely complex, and since it is in the nature of these fi lms not to rely on any visual continuity, it is almost always necessary to add a commentary. The commentary is written at the script stage and fi nally amended to fi t in with the timing of the visuals. It is the editor’s task to fi t the words of the commentary to the images in such a way that they reach the audience at exactly the right moment. As we shall see in the example quoted below, the correct timing of words and picture is a most important factor in achieving a concise and completely clear result.
On the other hand, it is generally not advisable to have the commentary going on all the time; pauses not only allow the audience to take in what the images are conveying, but also give the opportunity to let the lesson sink in. The function of the commentary is primarily to keep the audience thinking in the right direc-tion; it is not to tell the audience what they can very well see on the screen.
In the example quoted below, the commentary is continuously employed to make the audience draw certain conclusions from the visuals; although it never describes the picture, it gives each shot a meaning in its con-text, by discussing the general principle which is being illustrated.
HYDRAULICS 2
Extract from Reel 1
The sequence quoted here is the introductory passage explaining the basic properties of liquids on which the principle of hydraulics rests:
(1) That liquids change their shape.
(2) That liquids are almost completely inelastic.
The rest of the fi lm shows applications of these principles.
2 Director: 1941 Ralph Elton. Editor: R. K. Neilson-Baxter. Petroleum Film Board, 1941.
Ft. come into frame and start washing.
— and closes tightly round a hand hand. The jug is tilted and camera fol-lows the stream of beer down to the pipe to reveal a man spraying the wheel of a lorry. under a bridge. One dives into the stream and then another.
Fill a bottle with liquid, right up to the cork.
12
15 C.S. Top of full bottle with cork in.
If we try to compress liquid into a bottle —
Little purpose will be served by analysing this sequence shot by shot, because it is simple and straightforward.
We can content ourselves with a few comments:
The sequence begins slowly — shots 1 and 2 are rather long in duration; this is done to give the audience time to settle down and be ready for the argument. The waves are shown (shots 1 and 2 ) partly to convey the power of liquids in motion — which is discussed later in the fi lm — and partly to make the fi rst point in the argument, namely that water has no shape of its own.
Mention in the commentary of a new point is always made to coincide exactly with its fi rst introduction in the visuals. The operative word “ solids ” is introduced at the exact moment when shot 3 begins; similarly, “ But liquids are not elastic ” coincides exactly with the belly-fl op ( 11 – 13 ).
Shots 3 and 4 introduce two facets of a new idea: shot 3 , that liquids take their shape from solids, and shot 4 , that liquids give way to solids. The two ideas follow logically because there is a visual connection between them, namely the basin of water.
The camera movement in shot 5 emphasises the point that water changes its shape in accordance with the shape of the container in which it is kept. If the operation had been shown in a static set-up, with both jug and glass in the same shot, the concept of the change of shape would have been conveyed much less force-fully. Similarly in shot 6 .
The dissolve after shot 13 is used to indicate the change in the approach: from the everyday example of the man’s “ dive, ” we are now taken to check the empirically reached conclusion by a laboratory test. The dissolve also allows for the laugh which might follow shot 13.
The commentary is needed over shots 14 and 15 because the audience might not otherwise know what con-clusion to draw from the visuals.
The sequence 16 – 20 may seem superfl uous because the whole experiment could have been shown in one
The sequence 16 – 20 may seem superfl uous because the whole experiment could have been shown in one