back to article Classic telly FX tech: How the Tardis flew before the CGI era

These days it’s all done with computers, of course. CGI – short for Computer-Generated Images, or Imagery – was a well established visual effects technique long before Doctor Who was rebooted in 2005, so it was never in doubt that on-set mechanical effects would be duly combined with CGI visuals during post-production. Both …


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  1. Anonymous Coward
    Anonymous Coward

    Trial of a Timelord Opening Shot

    The opening effects sequence of Trial Of A Timelord are still stunning. First use of a motion control camera for a UK TV series. IIRC. Cost them 20 grand in 1986 money which was a huge amount in terms of the episode budget at the time (don't have 1986 figures, but in 1989 Who was 100 grand per 25 minutes). Inflation allowing it's expensive by the standards of the new series as well.

    The 1987 titles were also ahead of other TV shows at the time. Produced on Sun workstations (IIRC) by a company called CAL Video, the producer was able to negotiate a considerable discount in return for an on-screen credit and the ability for CAL to be able to link themselves to some high profile CGI work.

    1. Anonymous Coward
      Anonymous Coward

      Re: Trial of a Timelord Opening Shot

      What about the 'special effects' used on the head-gear of the female prosecutor.... :) I love the Doctor and all the wobbly sets on B7 too! TV at its most imaginative!

    2. David Given

      Re: Trial of a Timelord Opening Shot

      It's a really nice shot, yes --- and a very effective opener for an ambitious story that I was thought deserved better than it got --- but those stars have always bugged me. I assume that they were *supposed* to look like that, given the care and attention that shot got, but I don't know why...

      I wonder what happened to the space station model?

      1. Anonymous Coward
        Anonymous Coward

        Re: Trial of a Timelord Opening Shot

        The space station model ended up at the Longleat exhibition. Sadly during the 1990's there was a fire and it was badly damaged. I think it still exists but is very damaged/melted.

        What's more annoying about that sequence than the stars is that when it was remastered for DVD they omitted some of the audio FX from the tractor beam bit that helped sell the shot.

        1. dmck

          Re: Trial of a Timelord Opening Shot

          I saw it a MOMI in the early 90s, stuck at an angle to fit in the room.

  2. This post has been deleted by its author

  3. swschrad

    on ChromaKey (tm)

    which was availiable in the mid-60s in NTSC, and was a patented and trademarked development of RCA. as usual, what was beastly expensive in the 60s became affordable to local stations by the early 70s, and widely licensed. our little TV stations in Fargo and Grand Forks, ND had Chroma (the licenses did not convey ChromaKey (tm)) on both Visual and Grass Valley switchers.

  4. Neil Barnes Silver badge


    It will always be CSO to me. Replace green bits with Tardis interior -->

    (Actually, I passed through the Tardis around 1980 vintage; I preferred the chairs from Blake's Seven.)

  5. Anonymous Coward
    Anonymous Coward

    bad cso illustrated by Timeflight

    We could try and pretend that it's the CSO lets down Time-Flight, but we'd be lying to ourselves. Rejuventating the cast and reshooting with modern effects couldn't save it.

  6. Anonymous Coward
    Anonymous Coward

    On a related note about sci-fi effects pre-CGI.

    I remember reading once that on Battlestar Galactica they needed wireframe ships to appear on the consoles in the bridge, so they spent weeks trying to get primitive CGI tech to display on CRTs. In the end they gave up and just spray painted some wire coat-hangers in a day-glow green, smashed out the CRTs in some monitors and hung the sprayed models inside the casings!

    1. Neil Barnes Silver badge

      Apropos of the Hitch Hiker's Guide...

      All the clever graphics for the TV series were done on film, sans computers.

      1. Michael Habel Silver badge

        Re: Apropos of the Hitch Hiker's Guide...

        Can we please have a new Hitchhikers TV reboot in 2018, (i.e. the 40th Anniversary?) please?

        I'd love to finally see an updated version of this, that can do the source material some justice!

        1. Dr?

          Re: Apropos of the Hitch Hiker's Guide...

          Whilst they're at it they could use some of Douglas Adam's Dr Who scripts in the rebooted series.

    2. Mike Moyle Silver badge

      Re: On a related note about sci-fi effects pre-CGI.

      On at least one episode of original Star Trek ("The Trouble With Tribbles", I believe) the U.S.S. Enterprise visible from a space station window was actually one of the AMT kit models hanging against a backdrop -- None of the regular Enterprise effects models was the right size.

      I've always loved the way that Dr. Who -- and Brit TV SF in general -- could make up in cleverness what they lacked in budget. Possibly my favorite was a "vortex in space" that it took me a couple of seconds to realize was just solarized footage of water going down a drain, superimposed over a starscape... Simple, effective, and cheap!


      Faking CGI

      In Escape from New York, the computer display of Plisken's combat glider was faked by putting glow-in-the-dark tape on their model of Manhattan and filming over it.

      That sequence holds up a lot better than other contemporary attempts to do genuine computer graphics.

      1. David Given

        Re: Faking CGI

        Hell, just go watch the original Tron. The CGI's okay, but the really stylish and striking scenes were just colourised black-and-white shots of the actors superimposed on traditional animation and hand-coloured. Although I wouldn't exactly call it easy --- apparently it was hideously labour-intensive.

  7. Johnny G

    Dodgy imagery

    I think some of those techniques are still being used by the North Korean propaganda team

  8. Vulch


    In the days of models they were quite often filmed upside down. Turns out the human eye is quite good at spotting strings above a model spacecraft wooshing across the screen, but not when the shot has been inverted so the string appears to be at the bottom.

  9. Phil O'Sophical Silver badge

    Nice history

    Thanks for the info, interesting reading, but I'l take issue with two small things:

    System A not only had 65 per cent of the vertical resolution of later standards, but it couldn’t do colour.

    System A did colour just fine, the BBC experimented with 405-line NTSC before finally settling on 625-line PAL and System I. They only broadcast System A colour experimentally, but it was more a case of "didn't" than "couldn't".

    So did transmitting colour data for effectively half the number of lines, though that was the result of PALs alternation of the colour signal’s phase to help correct phase errors by cancelling them out.

    Not quite, that is how SECAM works, it alternates the Y-R and Y-B line by line at transmission, transmitting at helf-resolution.

    PAL transmits both on each line, simultaneously modulated onto the colour subcarrier, with full vertical resolution, just as NTSC does. Because the resulting phase modulation of the carrier is subject to distortion over the signal path, which in NTSC gives the classic red grass/green faces problem, PAL reverses the phase on each line. If there is, say, 10% distortion it ends up in the receiver as +10% on one line, -10% on the other, and up to about 20% that cancels out visually in the viewer's brain.

    To get better cancellation, later PAL receivers used a delay line to save up one line's signal and electrically average it with the next one. That is what gives the half-resolution colour reduction, but it's done at the receiver, not in the transmitted signal. SInce the eye is much less sensitive to colour resolution than brightness resolution this goes unnoticed anyway.

    1. Outcast
      Thumb Up

      Re: Nice history

      In the words of the late Ian Dury..

      "There ain arf been some clever barstewards - Lucky Bleeders"

  10. Anonymous Coward
    Anonymous Coward


    Doctor Who was instrumental in the use of CSO at the BBC. The production team among the first to embrace it and used it heavily.

    Indeed the Who producer was asked to create an in house video to explain the technique to production staff of other shows who might be considering using it. The video used to be on Youtube but alas I can't find it at the moment.

    Around the same time the BBC acquired a machine to play back slow motion footage. It did this via a magnetic disc not unlike early computer hard disks, except it recorded analogue video.

    The machine was hideously expensive and very fragile. While this new wonder machine was being used on Who, it was discovered that if you gave it a kick it would produce some very interesting electronic effects that were great for making it look like whatever was on the screen was being electrocuted. So they did exactly that, they kicked the machine! Thus the zapping effects on the story Ambassadors Of Death were created.

  11. Anonymous Coward
    Anonymous Coward

    It's amazing...

    What the BBC could do in the 70s and 80s.......

  12. Anonymous Coward
    Anonymous Coward

    Well, someone will have to mention the SFX in 2001... I just did

    1. ThomH

      Re: Well, someone will have to mention the SFX in 2001...

      You mean the slit-scan photography, as most famously used by Who in the Tom Baker title sequence? That's actually a fairly easy idea for most computer scientists to grasp. You know how parallax scrolling works in video games? You know how by the early 1990s they were routinely doing every single scan line individually to give apparently perspective to floors and ceilings?

      Imagine you created that effect visually by cutting a horizontal slice in a piece of card and suspending that a distance above a colourful 2d image. Then light the image and make everything else pitch black. Take a single frame of film by pointing the camera at the slit and moving it directly towards or away from the surface.

      The effect is that the only part of the film that's exposed is that which can see through the slit. As the camera moves, the slit moves within the frame to expose a different part of the 2d image and you're now closer to the image so its larger. So you get an apparent 3d transformation of the 2d image built up with a continuous equivalent to the parallax floor.

      Move the background image a little and repeat for the next frame. And again. And so on. Then you've got the pattern apparently coming towards you.

      Then cut a more interesting shape than a horizontal line and add Tom Baker's face on top.

      1. Anonymous Coward
        Anonymous Coward

        Re: Well, someone will have to mention the SFX in 2001...

        Nope, I didn't mean the slit-scan sequences but the model and instrument display graphics work, which still don't look dated and which made early real CGI attempts look pretty poor in comparison (compare the high-res instrument displays in 2001 with the relatively low-res efforts in Star Wars etc.).

        Thanks for the explanation on slit-scan photography but I actually coded some stuff to churn out animation frames a few years ago.

  13. Christian Berger

    Bluescreen as it was called in German... works when you have the raw RGB data from your camera. Since VTRs back then only recorded composite video, you could only derive the keying from live video in any decent quality. So you'd get your RGB video into your keyer which then controls your mixer to mix composite video. This works fairly nicely in PAL or NTSC.

    BTW PAL doesn't actually have "colour every second line". It has an optional feature to average the colour between 2 consecutive lines to get rid of certain impairments. Monitors for home computers typically choose not to do this resulting in full vertical resolution chroma. (though with the usual small horizontal resolution)

    However you cannot mix SECAM that way since the chroma is FM. A SECAM studio actually needs to transcode the composite video to components, mix them, and then convert them back. That's a rather lossy process. In effect heavy SECAM shows like "Les Gammas Les Gammas" you can see how bad it can look. SECAM countries also were among the first to go component.

  14. Christian Berger

    BTW there was other stuff, too

    For example "Scanimates" which essentially consisted of some cameras, an analog computer and a CRT screen. You could feed the deflection signals through that analog computer.

    If you were a boring German, the result would look like this:

    If you had some more creativity and you did multiple passes, you could do things like this: (note the generous use of mock-3D and a tiny big of real 3D)

    or even something like this: (starting ag around 0:25)

    This usually involved ping-ponging video between 2 VTRs and adding layer after layer of motion. For this you needed the best VTRs you could get which back then where IVC 9000s. They were apparently so good you could go down 29 generations. The company went bust after shipping 69 (or so) of them. The BBC had only 2.

    Eventually digital disk recorders became available which could store several minutes of, obviously uncompressed, video. Additionally there were digital video effects, essentially a dedicated box which could store a whole video frame and distort it digitally.

    You could layer those effects by using hard disk recorders and later even digital video tape to create fairly nifty mock 3D.

    Of course in the hands of the Germans you get something like this:

    Or with the right drugs something like this: (Note the colouring which could be done by quite a lot of machines, many video artists even built their own video colorizer)

    1. David Given

      Re: BTW there was other stuff, too

      ...the globe in the last shot reminds me of the old BBC1 ident, which showed a spinning globe against a distorted map moving in sync. This was generated with the following wonderful piece of lateral thinking:

      That's the best shot of the kit I could find, but there's more info here:

      1. Anonymous Coward
        Anonymous Coward

        Re: BTW there was other stuff, too

        That was the NODD, or Nexus Orthicon Display Device. The footage generated was treated in the vision mixer live to give it a colour (older readers will recall first of all it was blue on black, then yellow on blue and finally lime green on blue).

        The successor to that was called the COW, or Computer Originated World. People sometimes assume that the COW played out from tape but it actually ran from a big metal box and really was proper CGI running live. Impressive for 1985 and probably very expensive.

        1. Robert Carnegie Silver badge

          Re: BTW there was other stuff, too

          I don't remember which comedy show it was that abused a version of the BBC globe and had it topple over and catch fire, but the design of the CGI one was borrowed to produce a see-through globe that turned until the continental patterns formed the faces of... that was Mel Smith and Gryff Rhys Jones, wasn't it? But Google Images doesn't seem to have that, so maybe I dreamed it.

        2. Christian Berger

          Re: BTW there was other stuff, too

          That's actually not the first "live computer created" video the BBC had. I think the animated BBC2 logo.

          It apparently was created by a machine having around 60 kilobytes of ROM. I haven't found the engineering articles about it yet.

          BTW the BBC also briefly experimented with recording digital data on video disks. That way they could do idents in high quality at low cost.

  15. Rog Reg


    I've long wondered why the field frequency of TV systems around the world tend to match the mains frequency. I'd been thinking about effects at the receiving end, and couldn't come up with anything. I just hadn't considered flickering studio lights before!

  16. Mike Banahan

    PAL and sync frequency

    The PAL trick of using a delay line and averaging colour over two lines got rid of 'Venetian blind' effect. The colour (chrominance) of the signal is dependent on the phase of the colour subcarrier, the saturation of the colour on its amplitude - just like NTSC (famously derided as 'never twice the same colour'). Phase linearity is VERY hard to achieve in cheap consumer grade electronics so the colour signal would often arrive way out of phase and that's what gives you lurid red or green flesh tones. Alternating the phase on each line allows the eye to average that out if the distortion is low, but it it's high, then each line looks noticeably different (Venetian blind effect). The delay line halves the colour resolution but gets rid of the visible effect by doing electronic averaging.

    Human eyes have very low colour resolution so nobody notices. If you ever see a tv picture with just the colour there and the sharp luminance edges of the monochrome signal removed it turns into just a mess of coloured blobs moving around and it's weird.

    Dear me, I can still recall from memory the 625 line 50hz colour subcarrier frequency after all these years: 4.43361875 MHz.

    Choosing a frame rate that's the same as the AC line frequency isn't about avoid strobing with studio lights. Those have massive filaments and thermal lag means you get little noticeable mains-related hum on the light signal. Again, it's the cheap consumer receivers with low-cost power supplies that you have to worry about. If the frame rate isn't the same as the mains frequency you get very noticeable strobing effects where light or darker bands appear to roll through the picture at the difference between the two frequencies and it's extremely distracting. A fixed darker or lighter bar can usually still be seen but it's much less annoying. Old valve sets usually were worse than transistorised ones and on those it wasn't unusual to see the dark (or light) bar slowly drifting up and down the screen when the national grid changed frequency to accommodate different load levels, the TV stations remaining locked to high-precision reference timebases.

    1. Neil Barnes Silver badge

      Re: PAL and sync frequency

      Spot on, Mike.

      Shortly after that, the sets got better but we still kept 50Hz timebase. The fun started when you wanted to insert an outside broadcast or another studio centre; the delays in the transmission circuits (curse that speed of light!) meant that you were guaranteed to be at least part of a line out and usually more.

      So Natlock was invented, which allowed the whole of the BBC transmission chain to be moved from the precision main oscillators to whatever the outside broadcast truck could manage - by tweaking the master oscillator frequency to match the OB a few microseconds a minute. When they were synchronised, you could cut between local and remote sources without a jump or a frame roll - while the change in frequency was too slow to upset the domestic receiver PLLs. Fast Natlock was used if you had multiple OBs that you needed to change to quickly; that dropped one line per frame and then used the slow method when you had at least the same field.

      Genlock was the same thing in reverse; you locked your local station to the network so that you could cut to the network through your vision mixer without a glitch, before running your local video.

      Of course, this all went away when digits came along since you could maintain everything to a common oscillator and just use a suitably long digital delay (eight fields covered all the options) but of course you now had an audio delay to accommodate...

  17. I Am Spartacus

    Thank you for this

    Tony, and all commentaries. This is a wonderfully illuminating thread on the complexities of early image manipulation. I worked with BSB up to the point of being bought out by Sky, but never on the video front. In any event, we were broadcasters rather than producers of video. And it was all done on Betamax-Professional if I recall.

    As I lie here ill in bed, it is great to have my spirits lifted by a discussion of early Dr Who footage and how it was done. So have a pint on me, but forgive, I won't be joining you

  18. Zot

    The worst effect I've seen on Dr Who.

    Using a BBC Micro (in mode 7, I believe) to display a sparkly effect in a room. Which means they used Teletext graphics to display square flashing blocks! I guess some guy knocked it up in 10 minutes on his computer, then they superimposed the blocks into the scene. It was horrible.

    1. Neil Barnes Silver badge

      Re: The worst effect I've seen on Dr Who.

      Not Dr Who, but vaguely related: when the first Shuttle was sitting on the stand I was working for BBC TV News. It turned out that we didn't have a system which could superimpose a running countdown onto the screen, along with all the holds that were happening - the usual super sources at the time were either a camera pointing at a black and white card, or the Riley machine which read paper tape and built letters using a diode look-up table.

      Using a Tangerine single board computer, I knocked up a blocky character set (the resolution was, IIRC, 2*3 blocks in a 32*16 array, so 64 x and 48 y pixels), and a bit of machine code that could generate the countdown and change as required. We pointed a camera at it and zoomed to fit... and then the editors decided not to use it!


  19. ecofeco Silver badge
    Thumb Up

    Excellent article

    More interesting history on Dr. Who as well as a very good primer on SFx.

    I've actually done photo compositing on a very nice Oxberry animation stand as well as Chromakey (green screen) work. Also used the Paintbox a few times and an Ultimatte.

    Now I can do all that on my home PC and then some. I'm still amazed.

  20. Henry Wertz 1 Gold badge


    Just a FYI, XVideo (and the Windows equivalent depending on the video card) use a window with a chroma key color. Usually it's all seamless but I dragged some text window over a video once and the font antialiasing must have used lots of blue, it bled through like crazy.

  21. Michael Habel Silver badge

    As bad as the SFX were back then, and let's be frank they were. Doctor Who was a who lot more then its SFX. The level, and detail of the Story telling in Old Who has IMHO never been surpassed even Once. Perhaps its my Rose* tinted Glasses, but New Who. just feels like the definition of throw away Television. I'll admit it had its moments, and the upcoming 50th Special on the 23'ed might prove to actually be watchable.

    But, since this is specifically about the SFX used between the Old & New Who. I have to say that that the Effects used on New Who are cold, and clinically dead. Kinda like the Writing.

    I can still remember whole seasons of Doctor Who, where the Doctor never Once went anywhere new the Earth.

    *BTW: Am I the only One that wants to kill themselves when they heard that they dug out Billie Piper again? If I had to point out One thing that was wrong with New Who. I'd say look no further. But, then I blame RTD for this!

  22. Anonymous Coward
    Anonymous Coward

    Can't help but admire the ingenuity of the early special effects guys, in the days of models and mattes. Just like the original Dr Who music was so pioneering, it now been replaced by some hideous faux-orchestral abomination that does no justice to the ground-breaking Delia Derbyshire and Dick Mills original. CGI makes it too easy and takes the wonder out of it, so it was refreshing to see the use of models returning in films like Moon.

  23. harmjschoonhoven

    Re: one-inch C Format tape

    The main advantage of the C-machines over the BCN-recorders which we used before - and after - that was that the C-Format allowed single frame recording.

  24. RAMChYLD

    PAL is not a TV system, it's a color system

    I think I should point out that PAL isn't exactly a TV system, it's a color system, like NTSC and SECAM. The true TV system in use in the UK is System I.

  25. Ralphe Neill
    Thumb Up

    Opening titles ...

    There was no mention (unless I missed something) of those moving "clouds" in the opening titles. And that was just video feedback ... pointing a camera at a monitor that carried the camera output. Impressive improvisations!

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