From: 0001964967@MCIMAIL.COM (Daniel Burstein)
Newsgroups: rec.arts.sf.tv
Subject: "Lost" episodes of Dr. Who
Date: 5 Sep 92 21:55:00 GMT

... the following is reprinted, without permission, from the 
British weekly "New Scientist" of 29-Aug-1992, p.21.  (I highly 
recommend it!)

Title: How Doctor Who was rescued from oblivion

by: Barry Fox

text: Using technology worthy of the Time Lords themselves, two 
video specialists working for the BBC have reconstructed a five 
part series of Doctor Who which was thought to have been lost.  
The BBC intends to show the restored series in January.

     The series, called "The Daemons", was first broadcast in May 
1991.  Unusually for the time, it contained many expensive 
external location scenes.  The series ended with a church being 
blown up, and this produced a storm of letters to the Radio 
Times.

     The BBC originally videotaped the series in colour, using 
the only professional video recorders available at the time, 
Ampex Quad recorders which used 2 inch (50 millimetre) tape.  But 
in the mid 1970s, the BBC erased large numbers of Quad tapes so 
that they could be reused.  All but one episode of "The Daemons" 
was wiped.

     The BBC had made two copies, however.  One was in colour on 
videotape using hte American NTSC standard, so that it could be 
sold to North American TV nations.  The American stations heavily 
edited the tape before transmission, to speed up the action and 
cut running time to make room for advertisements.  The edited 
version was broadcast in 1977 and the tape was then wiped.  The 
BBC's other copy was on black and white 16-millimetre film for 
sale to African countries which were not then broadcasting colour 
tv.

     Ten years later, when Doctor Who had become a cult series, 
the BBC realized it only had a black and white copy of "The 
Daemons".  By a stroke of luck, a British fan of the series met 
an American fan who had made a recording of the edited US 
transmission, using one of Sony's first Betamax home video 
recorders.

     The British fan copied the Betamax tapes onto professional 
U-Matic video cassettes.  The BBC got hold of these cassettes and 
asked James Russell, a video system designer with the British 
company Rank-Cintel, and also a fan, to try to restore the 
series.  Russell joined forces with Ralph Montagu, a graphics 
designer at the BBC, to find a way of blending the colour, or 
chroma, signal from the US recording with the monochrome, or 
luminance, information from the film.

     Russell and Montagu first ran the 16mm film through a 
telecine machine, which records the luminance signal from the 
film onto modern Betacam videotape.  Next they converted the 
American NTSC tape into the PAL standard used in Europe, and 
recorded that onto another Betacam tape.  The two tapes were than 
run simoultaneously and synchronized using digital time codes so 
that the colour signal from one tape could be mixed with the 
luminance signal from the other.

     The two signals did not quite match.  The luminance signal 
was distorted because when the series was copied by filming a TV 
screen, the geometry of the cathode ray tube distorted the shape 
of the picture.

     To correct for this, the restorers converted the signals 
into digital code and processed them using a special effects 
computer, the type which allows programme producers to twist TV 
pictures into dramatic shapes.  They twisted the picture back 
into its correct shape, so that the colour and luminance images 
matched exactly.

     The biggest challenge was to reconstruct sequences which had 
been edited out of the US version, and where only the black and 
white copy existed.  The engineers added colour by hand with a 
Paintbox special effects unit, using what remained of the uncut 
original scene as a guide.  One 20-second scene took two hours to 
rebuild.  In all Russell and Montagu took more than 40 hours to 
rebuild the 125 minute series.

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