Studio and Master Control Room Equipment
Vision mixing equipment is used in production control rooms, continuity and master control suites. Although there is some overlap between the different operating techniques employed, this section mainly deals with vision mixing in programme production.
Button Pushing
The operational aspects of a vision mixing control panel can be mastered in a matter of hours. The ability to switch visual sources either by a cut, mix or through the digital effects bank is relatively simple to master. It would be a mistake to conclude (and this applies to all television production craft operations), that knowing which button to push will convert you into a vision mixer.
There are a number of essential skills that separate a vision mixer from someone who knows how a vision mixing panel works. A competent vision mixer is someone who can work with split second timing so that a cut is taken precisely at the point the action requires, but who is constantly monitoring the previews to see if it will conflict with the mechanics of collecting the shot. They will have the ability to divide their attention between script, director’s instructions, preview monitors and audio.
Good vision mixing, like much of television production technique, is often a question of instant decision making, fast reflexes and complete operational integration with the rest of the production crew. In high-speed cutting on a complex show there is almost a telepathic link between director, vision mixer and camera crew. In ad lib situations when cutting between cameras constantly changing shot, the vision mixer and the camera crew know, from a knowledge of the programme format, what shots should be offered and taken. There is no more frustrating television than missing the right shot at the right moment. One of the skills developed by a vision mixer is knowing when to wait for directions to cut, and when to take the cut before the moment is lost.
Working in ‘Real’ Time
One of the fundamental distinctions that exists between multi-camera and single-camera techniques is that ‘film-style’ production splits its production decisions between acquiring the basic material and then editing the material. Live, and much of recorded television, requires all the options closed at the time of transmission/recording. Editing decisions on the precise moment of a cut have to be taken in ‘real’ time unlike the more considered decision making in an edit suite where a cut can be rehearsed, trimmed, rethought, and then executed.
The basic vision mixing activity is switching visual sources when directed. With a scripted show, the cuts will be rehearsed and often the director will not call them on transmission. On an ad lib show, where the precise nature of the content is not known, the director will call most of the cuts, but at moments of high activity when they are fully engaged, they may leave an experienced vision mixer to follow the action and cut as appropriate.
As split second timing is often involved, the vision mixer must have a good sense of the programme format conventions and the customary technique used in order to stay with the director’s requirements. For example, they must know the rules of the sport being covered, or have a feel for rhythm and mood when covering music, or roughly know the possible attitudes or opinions of participants in a debate. So often in live television, the speed of the technique is controlled by the content of the programme, and there is no time ‘on air’ to be precisely directed though all the vision mixing operations required. The director, vision mixer and camera crew activities are linked by the tempo of the event and must all be attentive to the immediate action and anticipate future events.
Vision Mixing and Video Editing
Both vision mixing and video editing share many common techniques. Whereas a vision mixer makes an edit decision in real time with little or no opportunity to adjust the point of edit, a video editor can rehearse and find a precise edit point before laying down the edit. They both, however, follow the standard, perennial conventions of shot transition. Although some of these conventions are dealt with in this chapter, a discussion in greater detail of the requirements of shot transition are to be found in the section on Editing, pages 138–169. There is some overlap of content.
Vision mixing a multi-camera production requires an understanding and how to effectively use all the facilities available on the desk in conjunction with the preview, effects and transmission monitors, and the ability to work in a team.
Although not appearing at first sight an important element of vision mixing, the physical relationship between the desk, script, monitors and control room lighting can be crucial. Every visual source required for the production should have a preview monitor or, if there are more incoming visual sources than monitors, control of the switching matrix should be easily accessible to the mixer.
The height and distance of the monitors should allow a rapid preview by the mixer without moving their body. Ideally this distance should be about six times the picture height from the viewer. There should be adequate space in front of the mixer for the script which should be directionally lit to avoid spillage on to the preview monitors. The ambient lighting in the control room should be designed to avoid reflections on the monitor display screens.
Synchronization and Timing
In order that all incoming visual sources can be mixed, wiped, superimposed, and processed through the vision mixing desk, it is essential that certain conditions relating to signal timing are met otherwise it is impossible for the mixer to perform correctly. These conditions require a timing accuracy of less than 50 ns for the syncs and a phase difference of less than 5° between the subcarrier reference bursts when transmitting PAL or NTSC. Every video signal passing through the desk must be aligned to achieve these conditions if it is intended to combine it with another visual source.
Digital Vision Mixing
Once an analogue signal has been converted to digital or the signal originates as a digital signal then a considerable number of effects can be produced via the vision mixing panel. Digital video effects such as picture in picture, freeze frames and picture manipulation have become a staple part of programme production.
The next step on from digital mixing has been the development of computer software to control visual transitions using graphical interface units controlled by a computer mouse. Although these add enormously to the flexibility in post production work, ‘real time’ vision mixers on live or recorded-as-live productions usually prefer the security of buttons, faders and source selectors provided by the traditional vision mixing panel.
The Importance of Monitoring
All preview and effects previewing should be available on high-grade colour monitors. The phosphors should match so that skin-tones of any individual face or object colour are the same on each monitor. Each monitor should be set-up for correct contrast and brightness. Every shot requires previewing for content, composition and exposure before it is cut to line (i.e. transmitted or recorded). Any large differences between monitors will prompt a visual ‘jump’ each time they are previewed inducing inefficient hesitation before selection.
The Importance of Communications
The vision mixer needs to confirm incoming video signal’s availability and where they will appear on the switching matrix before transmission/recording, and often needs to query the availability of lines and their source on transmission. Good communications between the control room and the operational point controlling switching and lines checks are therefore essential.
The controls on the mixing panel allow several basic visual transitions. These include:
A cut is the simplest switch between shots. One image is instantaneously replaced by another image.
Dissolve or mix (also known as a cross-fade) allows the incoming shot to emerge from the outgoing shot until it replaces it on screen. Sometimes both images are held on screen (a half-mix) before completing the transition. The time taken for the dissolve to make the transition from one image to the next can vary depending on content and the dramatic point the dissolve is making (e.g. a slow mix on slow music, etc.). The proportion of each image present at any point in the mix can be varied, with one image being held as a dominant image for most of the dissolve.
Fade is similar to a mix except only one image is involved and either appears from a blank/black screen (fade-in) or dissolves into a blank/black screen (fade-out). A fade-in is often used to begin a sequence whilst a fade-out marks a natural end to a sequence.
Superimposition is when one image (often text, such as the name of the speaker on shot) is superimposed on top of another image. Name-super text is usually faded-in or wiped-in, held so that it can be read, and then faded-out, cut-out or wiped-out.
Wipes and pattern wipes provide an edge that moves across the screen between the outgoing image and the incoming image. The edge may be soft or bordered (a soft-wipe, or a border-wipe) to add to the transition visually. Common wipe patterns are a simple box or circle, stars, heart shapes and other geometric shapes.
Split screen is when two different images are held on screen separated by a hard or soft edge wipe.
Digital video effect (DVE). When a picture is digitalized the image is formed by millions of separate parts called pixels. These pixels can be endlessly rearranged to produce a variety of random and mathematically defined transitions such as geometric wipes, spins, tumbles, squeezes, squashing, and transitions from one image to another, simulating the page of a book, for example, being turned to introduce the next image.
Colour synthesizers is a method of producing coloured captions and other effects from a monochrome source. The synthesizers rely on an adjustable preset video level to operate a switch, and usually two or three levels can be separated and used to operate colour generators and produce different colours. The switching signal is usually derived from a caption generator.
Chroma key is a method of combining two images to achieve the appearance of a single image (see Chroma key, page 190).
The output of the mixing panel is via a master fader although additional visual inputs can be added by a downstream keyer (see below). A basic mixer has two selection banks, normally termed A and B, and mixing or effects is performed between the two banks. Normally, each camera in use in the production has a dedicated button numbered in sequence from left to right as 1, 2, 3, 4, 5, 6, or however many cameras there are. Selection of other video sources can usually be switched to the required button with both banks duplicating the visual sources. Cutting between video sources is achieved by selecting one of the banks and then depressing the appropriate button on that bank.
Mixing between video sources is achieved by selecting the incoming video source on one bank and the outgoing source on the other bank. A pattern wipe on the transition can be achieved by routeing the mix through the effects generator.
As well as an A and B bank, a C and D bank allows previewing of pictures prior to selection on the operational banks plus the ability to mix to a combination of two visual sources. For example, an image selected on the C bank with a superimposed caption selected from bank D can be mixed to the output of banks A and B.
A black input is available so that a correct waveform is transmitted when the pictures are faded down.
A downstream keyer is a facility in-line with the output of a vision mixing panel which allows a superimposition on the output of a mixer panel which is unaffected by any changes on the mixer panel, e.g. a caption can be superimposed over changing shots selected at the mixer.
A digital vision mixing panel enables the most complex and sophisticated transitions between video sources that may be required in programme production. However, the vision mixing activity that is not available on any desk, and is crucial to programme production, is which vision source should be selected, and at what precise moment should that transition occur. Technology cannot help with these production decisions, and anyone new to vision mixing will have to learn the underlying principles of why change shot and when to change shot.
As we have discussed in Section 2, Television production, continuous camera coverage of an event using a number of cameras relies on a stream of invisible shot changes. Invisible in the sense that the transition between each shot does not distract the audience. The aim is to make the shot change unobtrusive to prevent the audience’s attention switching from programme content to the programme production technique. No shot can be viewed in isolation – its effect on the viewer will be related to the preceding and succeeding shot. Standard conventions are employed, when cutting between shots, to ensure a smooth flow of images to guide the viewer unobtrusively to a new viewpoint.
Basic Conventions
After mastering the operational controls on the vision mixing desk, the next stage is to fully understand these editing conventions. For a shot change to be unobtrusive:
there must be an appropriate production reason to change the shot
the shots either side of the visual transition (cut, wipe, mix) must satisfy the editing requirements that link them.
Visual Perception
Moving images in television are created by a repetition of 25 complete ‘freeze’ frames per second. It is human perception that combines the separate images into a simulation of movement, (see Perception and shot transition, page 148). The greater the visual discrepancy between two shots the more likely it is that the viewer will consciously notice the change of shot. A basic technique of vision mixing is to find ways of reducing the visual mismatch between two adjacent images (see text box opposite).
Matching the visual design of shots is discussed in more detail in the section on editing (pages 138–169). The majority of studio work that the technical operator may be vision mixing will concern shots of people in discussion, and the transition from live to recorded items. Most of the following topics have been dealt with in the section on multi-camera camerawork but the important points for vision mixing are emphasized below.
The standard production reasons for a shot change are:
to follow the action (e.g. coverage of horse racing – as the horses go out of range of one camera, they can be picked up by another and so forth)
presenting new information (e.g. a wide shot of an event shows the general disposition, a close-up shows detail)
to emphasize an element of the event (e.g. a close-up shot revealing tension in the face of a sports participant
telling a story (e.g. succeeding shots in a drama)
to provide pace, excitement and variety in order to engage and hold the attention of the audience (e.g. changing the camera angle and size of shot on a singer)
to visually structure an event in order to explain (e.g. a variety of shots of a cooking demonstration that show close-ups of ingredients and information shots of the cooking method).
In general, a change of shot will be unobtrusive:
if the individual shots (when intercutting between people) are matched in size, have the same amount of headroom, have the same amount of looking space if in semi-profile, if the lens angle is similar (i.e. internal perspective is similar) and if the lens height is the same
if the intercut pictures are colour matched (e.g. skin tones, background brightness, etc.) and if in succeeding shots the same subject has a consistent colour (e.g. grass in a stadium)
if there is continuity in action (e.g. body posture, attitude)
when cutting on action – the flow of movement in the frame – is carried over into the succeeding shot (e.g. a man in medium shot sitting behind a desk stands up and on his rise, a longer shot of the man and the desk is cut to)
if there is a significant change in shot size or camera angle when intercutting on the same subject
if there is a significant change in content (e.g. a cut from a tractor to someone opening a farm gate)
if there is continuity in lighting, in sound, props and setting and continuity in performance or presentation
Eyeline is an imaginary line between an observer and the subject of their observation. In a discussion, the participants are usually reacting to each other and will switch their eyeline to whoever is speaking. The audience, in a sense, is a silent participant and they will have a greater involvement in the discussion if they feel that the speaker is including them in the conversation. This is achieved if both eyes of the speaker can be seen by the viewer rather than profile or semi-profile shots. The cameras should be able to take up positions in and around the set to achieve good eyeline shots of all the participants. That is, both eyes of each speaker, when talking, can be seen on camera. In addition, the relationship of the participants should enable a variety of shots to be obtained in order to provide visual variety during a long interview (e.g. over-the-shoulder two-shots, alternative singles and two-shots and group shots, etc.). The staging should also provide for a good establishment shot or relational shot of the participants and for opening or closing shots.
Standard Shot Sizes
Because so much of television programming involves people talking, a number of standard shot sizes have evolved centred on the human body. In general, these shot sizes avoid cutting people at natural joints of the body such as neck, elbows, knees. See Section 4, Multi-camera camera-work (pages 48–77) for illustration of standard shot sizes. Precise framing conventions for these standard shot descriptions vary between studios, broadcast organizations, and country. One director’s MCU may be another director’s MS. The reason abbreviations are used is to speed up communication on live broadcasts. Make certain that you understand how the abbreviation is being used by the production team that you are working with.
Cross Shooting
A standard cross shooting arrangement is for the participants to be seated facing each other and for cameras to take up positions close to the shoulders of the participants. The usual method of finding the optimum camera position is to position the camera to provide a well composed over-the-shoulder two-shot, then zoom in to check that a clean single can be obtained of the participant facing camera. A tight over-the-shoulder two-shot always risks masking or a poorly composed shot if the foreground figure should lean left or right.
Crossing the Line
There may be a number of variations in shots available depending on the number of participants and the method of staging the discussion/interview. All of these shot variations need to be one side of an imaginary line drawn between the participants (see Section 4 Multi-camera camerawork).
Matching to other Cameras
In addition to setting up the optimum position for singles, 2 shots etc, shots in a multi-camera intercutting situation need to match. The medium close-ups (MCUs), etc. should be the same size with the same amount of headroom. All cameras intercutting on singles should be the same height and if possible roughly the same lens angle (therefore the same distance from their respective subjects), especially when intercutting on over-the-shoulder 2 shots. This avoids a mismatch of the perspective of mass (i.e. the background figure is smaller or larger than the shot it is matching to). Other matching points are the same amount of looking room with semi-profile shots by placing the centre of the eyes (depending on size of shot) in the centre of frame.
Interview Format
The main points about cutting an interview have already been discussed, but the following additional points should be noted.
The director should establish in rehearsal on which camera the presenter will make their introduction.
The camera coverage and the order the participants will be introduced should also be established so that vision mixer can mark up. A frequent problem in this part of the interview format is the presenter names the participants too quickly giving little or no chance for the cameras and the vision mixer to get the appropriate shot up as the person is named.
Try and establish who the first question will be addressed to if it is known before recording/transmission.
Establish with the director if he/she will call for reaction shots, although the best reactions are so quick that if the cut is not taken immediately the ‘reaction’ is lost.
A popular convention is to cut to the participant who is being asked a question before the presenter has finished the question in order to observe their reaction to the point being put to them. Check with the director if they intend to follow this convention.
It is not a good idea for cameras to make large repositions during an interview as the speed of question and answer may result in a camera being on the move when it is required to be on a participant. An experienced camera crew will inform the director in rehearsal if they are repeatedly having to make large off-shot movement to provide the camera coverage he or she requires. The vision mixer can only watch the preview monitors and hope that the required shot will be steady, focused, and with a matched frame when it is required.
If the presenter does not name the person they are coming to, watch the preview monitor of the wide shot or the presenter shot to check their eyeline to establish who he or she is addressing before making the cut. It is better to be a beat behind the answer than cut to the wrong person.
Different programme genres have different production techniques. Sports coverage has different shot patterns and camera coverage conventions, for example, to the conventions used in the continuous coverage of music. Knowledge of these customary techniques is an essential part of the vision mixing skills that need to be acquired. There is usually no time for directors to spell out their precise requirements during a fast, live transmission. They assume that the production team is experienced and understand the conventions of the programme being transmitted.
Programme Formats
For a vision mixer, a basic distinction is whether the production is scripted (e.g. cuts to dialogue or narration are pre-planned and marked up in the camera script), or if the majority of the programme speech is unscripted. With this type of ad lib production, the vision mixer will need to follow direction, and, at times, make edit decisions when the director is otherwise involved. At an early stage in rehearsal, establish with the director whether they wish to call every cut or if they are happy for the vision mixer to take the appropriate cuts in an interview when needed.
‘As-Directed’ Procedures
‘As-directed’ procedures require fast reflexes and an awareness of the development in programme content. Sometimes a programme will have sections which have a rehearsed shot structure interspersed with ‘as-directed’ sequences. The danger point is the junction between the two. It is easy to be caught in the ‘as-directed’ mode of operation and unable to find the correct place in the script when the programme moves into the scripted, numbered shot sequence.
Scripted Programmes
A production that has been precisely camera scripted would seem an easier option than continuously keeping up with unexpected dialogue and discussion, but this is not necessarily the case. The scripted shots and cutting points need to be proved with a rehearsal. Those that do not work need altering and in a very fast cutting sequence, each shot has to be taken at its appointed place otherwise everyone, from the PA calling shot numbers to the camera crew working precisely to their listed shots, lose their place. A tightly scripted production requires the vision mixer to clearly mark-up all the changes during the rehearsal, and to be satisfied that all the vision mixing requirements (e.g. DVEs, chroma key set-ups, etc.) can be achieved in the time available as the production progresses in the time scale of the event being covered.
Any subject covered by multi-cameras must follow standard basic space/time visual conventions if the resultant flow of images is to be intelligible to the viewer. These shot change conventions ensure that:
shots are structured to allow the audience to understand the space, time and logic of the action
each shot follows the line of action to maintain consistent screen direction so that the geography of the action is completely intelligible
unobtrusive camera movement and shot change directs the audience to the content of the production rather than the mechanics of production
continuity cutting creates the illusion that distinct, separate shots (possibly recorded out of sequence and at different times) form part of a continuous event being witnessed by the audience.
Vision Mixing and Video Editing
See topics on editing, pages 138–169 for more detailed description of methods of shot transition, rearranging time and space, basic editing principles, types of edit, matching visual design between shots, matching spatial relationships between shots, matching temporal relationships between shot, cutting on dialogue, etc.
Standard Openings
The opening of a programme is often deliberately designed to be fast and engaging to hook the audience. It will often follow a standard pattern that establishes the programme’s identity (e.g. the headlines of a news programmes). Often the director will rehearse the opening, even if the main part of the programme will be ‘as-directed’. As a vision mixer, it is worth marking up your script in detail and snatching some time for yourself to go through all the effects, routine and desk set-ups that are needed. Do not rely on memory. Put it in writing on your script, even if you never read it. Make certain that you are technically clear on what you have to do and can cope with last minute changes if they happen. A common problems is the non-appearance of a contributor at an outside source who is to be featured in a scene-setter at the beginning of the programme. Anticipate that this may not happen and have a fall-back plan of what you will do if they fail to arrive.
It is particularly important to get the show off to a good start in order to grab the viewer’s attention, and also because mistakes at the start can lead to a ‘domino’ effect that will ripple all around the production team and take time for everyone to return to competent operation.
Standard Close
Many programmes also have a standard close. Three things often happen in quick succession. The presenter will wind-up the show, there may be a closing wide shot sometimes with a lighting change for closing graphics or credits to be supered over. The perennial problem with a live programme is time. If an interview precedes the close, the vision mixer will have been involved in a close and concentrated cutting sequence and may neither have anticipated nor set up the desk for the final sequence. At some time before the end you must anticipate what is required. A programme often crashes out because a contributor will not take a wind-up, and there is inadequate time remaining for the pre-timed music and end credits. Arranging for the credits and music to end together is the usual professional aim for the end of a show. Be prepared with the end sequence before it is required.
It is crucial in a fast ad lib spontaneous programme that the vision mixer and camera crew are on the same ‘wavelength’ as the director. This means everyone understands the customary technique for the programme and think in the same way. In practice, this means that when everyone anticipates a cut, it happens. Or when everyone anticipates a specific shot, it is taken. If a camera crew or vision mixer are puzzled by the cutting preferences of the director and it does not follow customary conventions then the director, in a fast moving ad lib production, will have to call every shot, and every cut, and this can be time consuming and inefficient. If everyone can keep in step, then the production team can up its work rate and still keep together.
For example, when a camera is ‘on shot’ on a interviewee and a neighbouring speaker out of shot starts to speak, the cameraman could pan in vision to the speaker, although this is usually not customary technique, or the mixer can cut-away to a quick reaction shot of the anchorman or group shot allowing the camera to quickly reposition ready for a cut back with hardly a word being lost on screen. When trust is built up between director, vision mixer, and camera crew many more shots are possible because repositions are faster. A cameraman may spot a person bursting to get into the debate and swing to them which usually prompts the speaker to speak. If the director wants to call every move and every cut and every shot they may miss a number of useful shots and, unless they are very lucky, be left several shots behind the flow of the discussion. Tying up several cameras solely as wide ‘belt and braces’ covering shots leads to a camera coverage that is too loose and does not engage and involve the viewer in the personalities of the debate.
In order for a topical daily magazine/news programme to be prepared, there is usually a well defined format with standard items and methods of presentation. Before working on such a programme, get to know the basic items which are going to appear on the daily running order and most importantly, understand the specific abbreviations or slang descriptions that are used by the programme production staff. Get someone to explain any jargon that is new to you because on transmission there will not be time to question what the implications of an unintelligible piece of information about changes to the running order that is thrown from the back of the control room to the director. You may be astute enough, for example, to work out that when the editor shouts out ‘Kill the heads’ that instead of going to presenter A on Camera 2 to read the closing headlines, the next shot will be presenter B on camera 1 who will then link to the weather report. The production team may have been working on the same programme format for many years and know instantly the rearrangement necessary when the headlines item is dropped. If it takes you five to ten seconds to decipher the insider jargon, you could be completely wrong footed and cut to the wrong camera. People who are in daily contact in the production of a programme have a habit of inventing shorthand descriptions of the daily items which only insiders are privy to.
The running order, although brief, is the key to what you as a vision mixer will need to know. Mark up any scripted links (which often arrive very late and sometimes while you are ‘on-air’) indicating camera and visual source in large letters (see Marking up a script, p. 198). Check the end words coming out of a recorded item as you will be listening for them to cut out of and back to the presenter. Some presenters will ad lib into an item and the cue to go the new item must be given by the director in order that both vision and sound can cut/mix at the same time. The director should always control any programme transition that requires coordination between sound and vision so that there is no misunderstanding causing sound or vision to lead or lag.
Keep up to date with changes, especially those last minute changes that occur in the last few seconds before transmission when everyone is checking sources, levels and setting the desk for the opening routine. Try to look ahead on transmission to any complicated set-ups that are upcoming such as chroma key weather set-ups (see Chroma key, page 190).
Name supers on recorded items need to be checked for accuracy and if there is sufficient time for the super to put up, read, and taken out before the shot changes. A timed list of supers and when they occur should be available from editing but be warned, if they have not been rehearsed the timings could be wrong.
On air, watch out for the invariable jokey interchange between presenter and weatherman or specialist sports reporter. Watch your previews to check that you can cut back to a presenter after going to the weatherman if the repartee continues because sometimes a camera will clear immediately a link has finished. Check also that your desk set-up allows you to intercut between weatherman/chroma key background and presenter. This type of ad lib cutting can be visually very messy because of its spontaneous content and indecision about when it has ended.
Early Morning and Late Night News Bulletins
Local news inserts into a network programme or regional opt-outs can often be pre-rehearsed and accurately timed, but from a mixing point of view, there is often the need to be flexible and adapt to the time actually allocated. If a network programme is over-running the squeeze is often on the opt-out in order to catch up on the overall running time.
A television demonstration can have as its subject anything from a DIY item to cooking a Christmas pudding. It is often conducted by a presenter and an ‘expert’ who will do the demonstration. The camera coverage will require shots of the two participants and close-ups of the demonstrated items. If the items can be positioned for clean CUs in rehearsal the demonstration will be that much more intelligible to the viewer. Be quick to cutaway from a small item that is held in big close-up and is being waved around by the participant. It is almost impossible to hold it in sharp focus and if it is waved around the viewer will not be able to understand the content of the shot. If tight close-ups are being picked up on a surface such as a table, be certain that the item is the one that is being referred to before cutting to it. Too often an interviewee will rest their hand on one item before discussing another item at the far end of the table. If in doubt, watch the two-shot on the preview monitor to check the direction of the eyeline.
Working in a Production Crew
Obviously the director/vision mixer wants the appropriate shot ready, in focus and steady when it is required, but for the cameraman there are a number of obstacles to achieving this. As a vision mixer, try to understand why the shot is not ready. It may be the cameraman’s fault, but more likely there is a cable problem or scenery or a dozen other reasons why the shot is not steady, in focus and on the correct subject. The preview monitors are a useful communication tool in these situations, and an experienced camera crew will show what the problem is (e.g. the floor manager has lost talkback, etc.) if they are not otherwise engaged ‘on-air’. Be consistent, on scripted shows, to cut as rehearsed as the cameraman may be relying on the rehearsed time to make a reposition or adjust framing. Likewise the cameraman must deliver the shot that was agreed and rehearsed to ensure the cutting is appropriate.
Last Moment Tweaks to the Shot Just as the Mixer Cuts
A recurring problem facing vision mixers is at the moment they are going to cut, the cameraman re-frames or makes a slight ‘twitch’ to the framing. There are a number of reason why this happens. The most common one is that the presenter/participant alters their body position before they speak forcing the cameraman to re-frame just when the cut is required. The vision mixer can only watch the preview monitor and think the same way as the cameraman and anticipate, for example, that he will recompose the shot when someone straightens up and hold the cut until the shot settles.
Vision mixing on an audience show is similar to an enlarged interview. It helps if the anchor person is always on the same camera, and that there is a safety shot showing a wide shot of the audience. When a group of experts are gathered there may even be a seating plan with an order of speaking. Frequently however, an audience discussion is a free-for-all with a need for the camera crew to rapidly find the speaker or even anticipate who the next speaker will be. The director must coordinate and communicate when duplicate shots turn up. The usual guidelines for mixing an ad lib spontaneous event is to watch the previews, cutaway quickly to allow cameras to reposition, and trust that an experienced director and camera crew will provide the appropriate shot. Establish with the director the opening and closing routines and make certain the anchorman camera is released to go to the presenter for the wind-up.
Multi-camera music coverage on television includes a wide range of musical performances, production styles and visual preferences. At one end of the spectrum there are relays from concert halls of orchestral performances that are often tightly scripted and in general have an unobtrusive technique where the emphasis is on matching picture to content with the minimum of visual interpretation. In extreme contrast to this ‘invisible’ technique, there are multi-camera coverage of rock groups where an attempt is made to capture the atmosphere and excitement of a live event. Cutting rate and shots seek to reproduce the liveliness and frenzy of the rave.
Most of the following points are generalized and all are not applicable to the individual ways of presenting music on television within the wide range of production styles practised. They are an attempt to make the vision mixer new to multi-camera music coverage aware of some aspects of production technique that he/she should consider when working on a continuous musical event.
The different methods of covering music continuously with multi-cameras without recording breaks or post production are itemized in the text box opposite.
Cutting to Music
It helps when cutting music to have a knowledge of music form, but the minimum skill that is required to be developed by a vision mixer is a feel for pace and tempo, and an understanding of bar structure. Most popular music is created around a 16 or 32 bar structure and the cutting rate and time of the cut happening will relate to this bar structure. Listen to a wide range of music and practise cutting on the beat.
Mixes are often used on slower tempo numbers. Remember that the cameraman will hold a static frame while the cue light is on. Sometimes the fader can be almost at its end stop with no hint of its image on the transmission monitor. The cue light will still be on, however, and the camera cannot clear until the fader is taken to the end stop and the cue light goes out. Match the speed of the mix to the music and attempt to imitate a sound technique which often uses a non-linear fade-up or fade-down. This technique fades the sound away so that the listener is not really aware when the music has gone. Something similar can be done with visual cross mixes and combination shots when images are brought in and taken out.
The different methods of covering music continuously with multi-cameras without recording breaks or post production can be grouped under the following headings:
Pre-scripted: The whole performance is structured and shots assigned to each camera using a score or a break down of the number (e.g. concerts or production numbers in variety shows). With complex music (e.g. an orchestral piece) the director, vision mixer and PA will be following the score with the PA calling shot numbers and bar numbers to allow camera moves such as pans, zooms and tracks to be precisely timed. This complex event is usually well outside the experience of a technical operator.
Camera scripted during rehearsal: After looking on camera at the performance, shots are structured by the director and each shot numbered. This shot sequence is then exactly reproduced on the recording or transmission.
Top and tail: The start and end of a musical piece is decided, leaving the middle section to be as directed.
Assigned roles: Each camera is assigned one or two performers or instruments and offers a variety of shots connected with them. This gives the director a guaranteed appropriate shot at any time.
As directed: No shot structure is assigned and each cameraman is directed and/or offers a variety of shots, checking that the shot they are offering is an alternative to the shot currently cut to line.
Invisible keying of one image into another requires the application of a perfect electronic switch obtained by appropriate lighting of foreground and background, correct setting up and operation of the keying equipment, a match between foreground and background mood and atmosphere which is achieved by lighting and design, appropriate costume and make-up of foreground artistes, a match between foreground artiste’s size, position and movement and background perspective achieved by camera position, lens and staging.
The control that selects the precise point where the colour key will operate is often situated on the vision mixing panel. This clip level control needs to be adjusted so that there is a clean switch between foreground and background images. Small detail in the foreground subject such as hair, can ‘confuse’ the keying equipment so that there is not a clean switch between foreground and background. This usually appears in the combined image as fringing around the hair. The clip level control needs to be adjusted to provide a perfect key. Problems also arise when clothing or other items closely match the background keying colour or there is colour spill onto the foreground subject from the background chroma key area. Smoke or glass items are difficult to chroma key with standard colour switching but linear keying eliminates the problems connected with transparency. It does not switch between foreground and background but suppresses the unwanted colour of the foreground (e.g. blue), and turns on the background image in proportion (linearly) to the brightness of the blue of the foreground image. Shadows cast by foreground objects can therefore be semi-transparent rather than black silhouettes.
Chroma Key Technique
A simple application would involve an artiste appearing against a blue background on one camera and a second camera looking at a picture or slide of a street scene. When these two pictures are used with chroma key the artiste will appear on the screen as if he is in a street. The blue background can be produced by either blue painted scenery or a blue lighted cyclorama. In a long shot within a studio, the blue backing is usually insufficiently wide or high enough. A box wipe can be set-up on the mixer with the background scene outside the box and the combination of foreground/background through chroma key, inside the box. To provide the illusion of artistes appearing behind objects which are in the picture into which the artiste is to be inserted, objects or flats painted in the keying colour are placed in front of the artiste to coincide with the foreground objects’ position in the picture. All cameras must be locked-off and alignment is performed by using a mixed feed viewfinder on the camera which shows both pictures. There are technological methods of allowing cameras to move in synchronization.
Chroma key technique requires a switch to be inserted in the signal chain which will electronically select the appropriate image. Blue is commonly chosen as the colour to be used as the separation key but other colours can be employed. When the chroma key switch is in use, any blue in the selected image (foreground) is switched out and that part of the frame which contained a blue object is blanked. The black holes left in the shot are now used as a stencil to cut out the corresponding portions in the frame of the background image. The parts of the background image that are within this template are inserted (as a perfect fit) back into the blank areas of the foreground image.
Picture Manipulation
One method of inserting one image into another is via the digital video effects bank on the mixing panel. The inserted image is reduced to the required size and then positioned by joystick control. The position can then be memorized and recalled during recording or transmission. Remember that some adjustment may be necessary of the memorized position because although the electronic memory is infallible, the camera operator has to rely on shot box setting (if available), a marked position for the camera mounting on the studio floor and perfect visual memory of what the combined shot looked like at rehearsal. Computers are better than people in repeating perfect positioning within the frame. The same problem can exist with combinations of computer graphics and camera shots.
The Split Screen
A spilt screen is another method of combining two images. Although the term is often applied to the method of combining two images separated by a vertical or horizontal wipe, it can also be applied to a composite involving box, circle, shapes, etc.
Caption Key
A caption key facility provides for sharper separation between lettering and background image. This improvement in legibility can be enhanced by a black edge generator. A colour synthesizer can be used to colour captions or backgrounds for captions.
Wipes
The speed of a wipe that moves across the screen between the outgoing image and the incoming image can be controlled manually or programmed to move at a specified speed. Check with the director during rehearsal when setting up and memorizing the speed that is required.
Floor Monitors
Frequently floor monitor feeds are switched at the vision mixing panel. A typical production requirement is for an ‘in-vision’ monitor to be switched at a specific point in the production. The monitor, for example, may be displaying a contributor for an outside location who will be interviewed by the studio presenter. When the interview is finished, the monitor, if it is still in vision, will require to be switched to possibly the programme logo or a similar graphic.
Floor monitors may also require switching during the production of programme formats such as game shows or slung monitors for audience, etc.
Good visual communication is:
simple – unnecessary detail is eliminated with not more than three or four competing subjects for attention
accessible – the main subject/topic is quickly understood as the message may be on the screen for a limited time
clear – television screens vary in size, technical quality and viewing conditions therefore the message must be legible even in imperfect viewing conditions
impactful – a visually dynamic design to compete, but not conflict, with surrounding visuals
unambiguous – the observer’s eye must be guided with unmistakable certainty to the principal message displayed.
In its original basic form, a still store was a digital piece of equipment that allowed a frame of video to be stored and accessed when required. One frame of video in a standard 625/50 picture includes 720 pixel groups, each made up of full resolution luminance pixel plus two half-resolution colour difference pixels – a total of 829,440 pixels. Sampled at 8-bit resolution, this creates over 6.6 million bits of data (6.6 Mb). Each uncompressed stored frame therefore requires 6.6 Mb of memory.
As the cost of memory has plunged, there has been a huge increase in the storage and computing ability of still stores, allowing many more programme production techniques to be executed to augment the original function of storage and retrieval of television images.
Dedicated (and open architecture) still stores can provide:
a high capacity of still images (e.g. up to 56 minutes of uncompressed video)
file management using data bases that classify each image by title, category, original acquisition date, keyword, etc., for rapid search, sort and fast selection. As each picture is recorded it is given a number and can easily be recalled
manipulation of the image size and position on screen for over-the-shoulder use
arrangement and storing of selected images into stacks to match the running order of the production
forming images into stacks for animation
preview facilities to check the next image to be accessed on air
acquisition of visual material from dedicated graphics machines, and input graphic files from many different computer formats
frame grabs from moving images with the ability to process and eliminate interfield flicker, etc., on the image
duplicate outputs to allow more than one ‘client’ to have access to the stored material and facilities
remote control of access (e.g. an operational panel in a production studio or OB control room), plus the ability to network to many different users
on-air control providing speed, accuracy and reliability
drag and drop selection of required image
a range of DVEs including wipes, transition and dissolves
storing and replaying video clips
keying signals to allow on-air semi-transparent graphics
and many more facilities, depending on equipment design.
Storing picture information digitally allows individual images to be recorded from many sources such as graphics machine, still store, or character generator one at a time. Material can be built up, adding elements from a number of different sources until the sequences of images form an animated clip when played-out. Individual frames can easily be edited into a new order and the playback speed can be altered or made into a loop.
Dedicated frame store equipment has developed to overlap the function of computer graphics, vision mixing, video editing, animation etc., but the ability to acquire, store, index and replay a still, or a sequence of images, remains integral to most productions.
A character generator originally began as a facility that allowed text to be entered via a keyboard. Various visual manipulations could then be carried out on the text and it could be stored, ready to be accessed when required. The main requirement was speed and reliability for on-air work. As the cost of digital computing power decreased, many more facilities were added and character generators can now include:
a vast range of font styles and size with the ability to incorporate new and unique typefaces. Text can be set in any colour with effects like a drop shadow, surround, or strap line added to make the type more legible against its background
manipulation of the text in its on-screen presentation such as real time dynamic titling effects, dissolve, roll, crawl, zipping, reveal in or out, etc., and flying text in 3D space. Three standard text movements are zipping (words or phrases appear on the screen letter by letter), roll (the text runs up the screen to a preset time, often matched to music in an end credit sequence), and crawl (a horizontal movement of text often from right to left)
as well as text, CGs can also generate shapes and areas of colour such as backings, charts, straplines, boxes, etc. and manage the design and storage of symbols or logos that can be recalled and positioned with text
a built-in still store
painting with pen and tablet
video capture and video clip management to import external video clips to incorporate with captions or graphics, and allow shrinking, repositioning, and zooming the external clip. A typical use is to squeeze down video clips and play them in the corner of the screen to promote up-coming items
dual/multi channel output
removable hard disks so that specific programmes’ stings and animated graphics can be instantly available when loaded
spell checker plus the capability of importing from a PC a text file which can be formatted into the current production style template of appropriate font, size etc., plus the ability to integrate with newsroom workstation systems so that graphics can be created at the same time as a news script is compiled. The potential to move files from different production areas avoids retyping, allowing the production team to directly compile lists of credits, titles, and name-super graphics.
A prime function of a CG is still to prepare text for the screen, but the expansion of facilities allows a greatly enhanced range of graphic treatment. For example, an animated programme logo can be added to each name super in the ‘house’ style of the specific programme. At a time of ever increasing programme outlets, programme identification is becoming more and more important in the quest for audiences. Many productions have created their own typeface to continually remind the audience of the identity of the programme.
Graphics are used in a number of different ways in television production. Each format has its individual technique and conventions:
Straplines: A strapline is a line of text supered over live action usually at the bottom of the frame. It can be static or crawled across the frame (see text opposite). It can be used to reinforce the main image and audio, or it can be used to add completely new information with the risk (and sometimes the intention) of conflicting with the background information. Name supers are frequently designed with the programme logo included.
Supered text: Any text that is required to be supered over moving images should be checked for legibility. If the background image varies in contrast and tone, a grey toned strap or edge enhancement can make the text more distinct.
Stacks, maps and charts: Specially designed maps are frequently used in news bulletins to show the location of the story. If it is a story about an unfamiliar country or city, a common convention is to establish neighbouring countries (or even continent), before focusing in on the designated area. Maps are designed to be easily read with the minimum amount of geographical information, cities, and towns, that are required by the story.
Words or pictures: Full frame graphics can be made up of text, pictures, symbols, or any combination of these. The information can be animated by building up the complete frame using a background image, and movement appropriate to the subject. The graphic presentation should be simple and uncluttered to allow the viewer to understand the main points being communicated.
Headings: Sometimes a story or a documentary uses a stand-alone graphic to identify a new subject or theme. These can be accompanied by musical ‘stings’ (a short musical phrase), all repeated in a similar style.
Quotes: Graphical text that is displayed to reinforce a voice-over should usually be identical to the words spoken. The viewer will read along with the spoken words and any difference between what is read and what is heard can be obtrusive and jarring.
Insets and over-the-shoulders: Most news bulletins use a chroma key window or DVE window sharing the news reader’s frame. The graphic displayed in the window can either be a generic logo (e.g. a football image for match reports), or a specific graphic to match the subject of the story (e.g. a politician image). Many programmes other than news and current affairs use over-the-shoulder graphics to support a piece to camera.
Outline points: With news stories, such as proposed new legislation, budget proposals, etc., the main points of the report are frequently built up, point by point, in the frame to form a summary of the changes. If each point is to be synchronized with voice-over replication make certain that the text is identical to the text read out or, if the summary is a ‘headline’ list, the spoken text enlarges on the keyword.
Marking up a Script
Vision mixing information on the script needs to be read at speed during transmission/recording. The size of the typescript is often inadequate to accurately check the next visual change when quickly looking between panel, monitor bank and script. The usual method of improving this is to write in large letters the camera number, instructions to cut, mix or fade and any other mixer facility to be used (chroma key, etc.). Identify key dialogue connected with visual transitions (e.g. changing graphic material in vision to match spoken commentary) or ‘in’ or ‘out’ words on insert material.
Why have a Rehearsal?
Multi-camera television production is a group activity. A live transmission requires the coordination and contribution of many different crafts and skills, each perfecting their input into the production at the precise time that it is required. A recorded item may have the luxury of retakes to eliminate imperfections if the programme content is under the control of the director (e.g. it is not an actuality event that cannot be repeated). To ensure that everyone is clear about their contribution to a transmission, the director/producer/editor must either brief each individual or arrange to run the item before transmission. A rehearsal provides the opportunity for everyone involved to check that the planned structure and detail of the programme is practical and achievable.
What a Vision Mixer Needs from the Rehearsal
As we have discussed, a camera scripted programme needs to be run in its actual running time to establish the feasibility of the planning. It is usual to block the shots, altering and adjusting the shots and cuts as necessary. Because this is a stop/start activity it is very easy to overlook the time available to carry out complex mixer set-ups or cameras to readjust the frame. A non-stop run of each complete section establishes the true time scale of the production. Make certain that you keep up-to-date with any changes and pay particular attention to fast cutting sequences to ensure that you, and the camera crew, have sufficient time to provide the shots and cuts on time. If you are working from a running order, the director should try to ensure that everyone has at least a look at each set-up and sequence, even if the shots are rehearsed with the floor manger standing in for absent presenters or interviewees. The running order should indicate visual and audio source, duration and any scripted intros or pieces to camera.
Talkback Discipline
Remember that a number of people are on talkback, with some wearing headsets for the whole of the rehearsal and transmission period. Avoid chattering on talkback about topics unconnected with the production.
There are a number of checks the vision mixer should carry out prior to rehearsal:
Check the script or running order and establish the origin of all visual sources and where they will appear on the mixer, and on what preview monitor.
Check source identification for incoming lines, and check if there are sufficient previews and sources on the mixer without the need to switch during transmission/recording.
Make certain you have a method of identifying and a written record of the origin of a source on the matrix if switching is required.
Check over the mixer and set up the facilities that will be required by the production.
Check that you understand how to rapidly use all the facilities available.
If it is the job function of the vision mixer, line-up the monitors with a test signal (e.g. PLUGE) if available and check for consistency in brightness, contrast, colour rendering and sharpness between previews and transmission monitors.
Check the cue lights on preview and transmission monitors, and with the camera crew/vision control, check the camera cue lights. If you are unfamiliar with the mixing panel check that cue lights still function when using the DVE facility.
At some time during the rehearsal, if you have not worked with the director previously, check on what cut decisions will be called and which mixing decision you should take from the script or programme content. The rehearsal period is also the time for you to assess the form of words with which the director will instruct you when he/she requires the edit points. It is not being pedantic to require good clear communication from the director to avoid, in the heat of a live production, misunderstandings and confusion. Someone snapping their fingers in front of your face is not clear communication unless they have preceded the signal with words such as ‘coming to 1. Cut to 1.’
Previewing
Many experienced vision mixers display the next visual source on the preview monitor. This may be impossible in an ad lib sequence but it does indicate to the director the upcoming shot. It is necessary for the director to be as brief as possible on transmission, but not to the point of unintelligibility. Shouting one word ‘cut’ when there may be choice of cameras to go to can only lead the vision mixer to assume the preview source is being referred to. This may not always be the director’s intention. There is a need for the director to stand the vision mixer and camera operator by before the instruction. This can be as simple as preceding the instruction with ‘coming to’. With experience, a vision mixer can react very quickly to content and the director’s instructions if there is some warning of their intention before the command is made. It helps if the director precedes an instruction, for example, ‘Camera 2. Give me a two-shot’. For a vision mixer, ‘Coming to 2. Cut’ or ‘Mix to four next … (pause) … and mix’. Be careful, when new to vision mixing, that you do not confuse a direction to a camera operator with a command to cut to that camera. This can easily happen if the director does not choose the instruction carefully.
On recording or on transmission there is no need for the director to call everything. The camera rehearsal period should have established the main structure of the show and the vision mixer should be confident of the flow of shots. On a fast cutting, scripted section, the less the director says the better. The director must however coordinate those transitions as, for example, coming out of a video insert, when both the vision mixer and sound need the command to make the cut coincide. The director should cue the artists so that by the time the cut happens, the artist is animated. The usual command is ‘cue and cut’. Mixing to a presenter takes longer than a cut and it is usual to use the command ‘mix and cue’ to allow the mix to be fully complete by the time the artist starts to talk. By the end of the rehearsal the vision mixer should know as much about the shot sequence and cutting points as the director. The director’s instructions during transmission or recording are merely an indication of when to do something.
A rehearsal exists to solve problems. What was a paper planning exercise has now to be converted into a three-dimensional activity for everyone concerned, all working against the hardest task master – the clock. Problems will arise, and sometimes sitting in your vision mixing chair you will feel you have the perfect solution. Depending on the moment, you can offer your suggestion, but make certain you have thought through all the implications and are not creating new problems elsewhere. Be cautious that one successful suggestion does not lead to a second and a third and so on. This is a diplomatic way of advising against trying to direct the show. There is only one director and all production communication should flow through the director’s chair.
It is a slippery slope to anarchy once everyone starts offering their viewpoint, and, as in the famous committee that set out to design a horse, your production team could end up transmitting a camel.
VT Clock
One final item to check on rehearsal for a recorded programme is the source of the ident clock and who is responsible for programming the correct details of the production. Make yourself aware of local custom and practice as to when you should fade to black before the top of the clock is reached.
Transmission/Recording Procedure
With a good rehearsal, by the time transmission or recording begins, the vision mixer should be fairly confident of what is their contribution to the production. Unfortunately the unpredictable nature of television is such that most experienced practitioners subscribe to the belief that a good rehearsal often presages a chaotic transmission. This pessimism is frequently unfounded and you should always attempt to get as much information about your production role before you go ‘on air’. If you are not told, ask, as the process of briefing everyone on the production crew can sometimes be less than perfect.
Anticipate the Unexpected
Television programme production is unpredictable, but its unpredictability often falls within a pattern. With experience, you can anticipate the unexpected and make appropriate alternative arrangements. Anticipation allows you to find time to do what is required. Being suddenly faced with a set of unrehearsed events without pre-thought eliminates any time to sort out the desk and make the correct operational decisions. Part of your preparation for the show is to mentally plan what you will do if the rehearsed sequences are changed. Set up complex effects before they are needed to make time for yourself. Keep with the flow of the production but constantly look ahead to what is upcoming.
Problems During the Show
No live or ‘recorded as live’ programme will be without its problems or unexpected emergencies. Artistes missing their marks or cameras prevented from getting to a prearranged position will require instant adjustment to the shot structure. Watch the previews for alternative shots. If you miss a shot or cut to a wrong camera, forget about it and make certain the next shot is there. Too often, the number of operational errors escalate because people spend time agonizing over their mistakes. If a shot is not ready and the director is unaware, bring it to their attention so that action can be quickly taken. If there is a production mistake on transmission, never spend time deciding on the cause. Get on with the next item and leave the post mortems until after the programme has finished. Remember to follow up equipment malfunction that affected your work and check that it will not occur next time.
Everyone makes mistakes, including the director. Sometimes he or she will call for a cut to a shot that is obviously wrong. The vision mixer in such circumstances will have to use their own individual initiative and a knowledge of the production to either cut to the right shot or if they feel this will cause greater confusion, go to the directed shot.
Summary of Vision Mixing Operational Technique
Preparation
know how the mixer operates
check over all the facilities and sources that are required
check and mark up the script
find out how the director will communicate with you
Concentration
keep your attention on the transmitted content even if every one else around you in the control room is concerned with items yet to arrive or which are unobtainable
do not try to do other people’s jobs (such as directing)
Anticipation
look ahead
anticipate what can go wrong
have a mental plan of what to do when it does go wrong