In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
On 12/05/2025 09:52, Chris J Dixon wrote:
In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
Google says it's about using colour reversal film instead of a negative
and positive. In this context, it might mean shooting the interviewer >pretending to be asking questions and nodding to the replies. I don't know.
In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
Max Demian wrote:
On 12/05/2025 09:52, Chris J Dixon wrote:
In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
Google says it's about using colour reversal film instead of a negative
and positive. In this context, it might mean shooting the interviewer >pretending to be asking questions and nodding to the replies. I don't know.
I reckon your first suggestion has it - you can edit the film as
shot, it doesn't need processing first.
Max Demian wrote:
On 12/05/2025 09:52, Chris J Dixon wrote:
In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
Google says it's about using colour reversal film instead of a negative
and positive. In this context, it might mean shooting the interviewer
pretending to be asking questions and nodding to the replies. I don't know.
I reckon your first suggestion has it - you can edit the film as
shot, it doesn't need processing first.
Chris J Dixon <[email protected]> wrote:
Max Demian wrote:
On 12/05/2025 09:52, Chris J Dixon wrote:I reckon your first suggestion has it - you can edit the film as
In Kirsty Walk's BAFTA acceptance speech, she said
"Things have changed so much, so radically, since the '70s, not
least the shoulder pads, the office drinks trolley, shooting on
reversal for a fast edit, and film crews, the size of football
teams,..."
Curious to know about shooting on reversal.
Google says it's about using colour reversal film instead of a negative
and positive. In this context, it might mean shooting the interviewer
pretending to be asking questions and nodding to the replies. I don't know. >>
shot, it doesn't need processing first.
I've never been directly involved with the film side but, from working
with a BBC film sound editor, I've always understood this is what it
meant
It needs processing, but only once, though if you have a decent
telecine machine, you can get usable results for broadcast off a
negative.
On 12/05/2025 13:57, Liz Tuddenham wrote:
Chris J Dixon <[email protected]> wrote:
Max Demian wrote:
On 12/05/2025 09:52, Chris J Dixon wrote: > In Kirsty Walk's BAFTA >>>acceptance speech, she said > > "Things have changed so much, so >>>radically, since the '70s, not > least the shoulder pads, the office >>>drinks trolley, shooting on > reversal for a fast edit, and film crews, >>>the size of football > teams,..." > > Curious to know about shooting on >>>reversal.
Google says it's about using colour reversal film instead of a
negative and positive. In this context, it might mean shooting the
interviewer pretending to be asking questions and nodding to the
replies. I don't know.
I reckon your first suggestion has it - you can edit the film as shot,
it doesn't need processing first.
I've never been directly involved with the film side but, from working
with a BBC film sound editor, I've always understood this is what it
meant
Not so good if you want to make multiple copies, but I suppose that's
less likely in TV rather than movies.
If I remember rightly, the sound guy carried the recorder, with an
umbilical lead to the cameraman. Four person crew, cameraman, sound guy, director/ minder and reporter.
I think it was mainly newsreel material that had to be got on air
quickly and then lost value. It could always be archived properly
afterwards if it was of future value.
I've have thought that well-exposed, well-lit reversal film was capable
of good results, because any colour cast could easily be corrected in
the telecine with the tilt-and-twist joysticks. Not as flexible,
perhaps, as photographic grading, where different coloured filters and exposures could be used for different shots, at the contact printing stage.
I've always wondered whether the fastest solution of all would have been
to shoot on negative (quicker to process than reversal film with its
extra light or chemical reversal process) and transmit from negative,
with the telecine handling the negative-to-positive conversion.
On Mon, 12 May 2025 21:08:38 +0100, NY <[email protected]> wrote:
I've always wondered whether the fastest solution of all would have been
to shoot on negative (quicker to process than reversal film with its
extra light or chemical reversal process) and transmit from negative,
with the telecine handling the negative-to-positive conversion.
It would have been just as quick, the telecines could easily handle
it, and it would have allowed a much greater range of exposure and
colour correction, and thus better picture quality.
But film editing tables were simply optical devices so the editors
would have had to work with negative images. Making a positive cutting
copy and then cutting the negative to match the edited result, as was
normal for big budget movies, would have cost extra time and expense.
Nobody would want to take the risk of broadcasting something without
being able to see it properly first, and some regional stations only
had one telecine machine,
Is there some fundamental reason why telecineing reversal film gives
poorer results than telecineing negative film? Can't the telecine make
the same exposure, contrast (gamma) and colour-cast adjustments from
either type of film?
Is film used much for TV documentaries and drama, or is it all
electronic nowadays? I've noticed that documentaries that are clearly
shot on video sometimes use separate sound recording - the modern trend
is to show a clapperboard being clapped at the beginning of interviews
while the subject is being introduced, something that was always edited
out in the days of film. Seems a bit of a retrograde step, making a
gimmick out of it.
NY <[email protected]> wrote:
Is film used much for TV documentaries and drama, or is it all
electronic nowadays? I've noticed that documentaries that are clearly
shot on video sometimes use separate sound recording - the modern trend
is to show a clapperboard being clapped at the beginning of interviews
while the subject is being introduced, something that was always edited
out in the days of film. Seems a bit of a retrograde step, making a
gimmick out of it.
AIUI that's also used when there are multiple cameras. eg if the presenter is doing a car review, there are multiple small cameras (GoPro or better) strapped to the car in various positions to get different angle shots. They're all recording locally, rather than being piped back anywhere.
Then they drive it down the road while chatting to the interior camera, and the edit cuts between various cameras all synced up. So when they tell us they put their foot down and we have footage of the exhaust making a noise, the editor can cut to it automatically aligned without having to do
anything.
In that instance the cheaper version of the clapperboard is to honk the
horn, which allows them to align the footage in the edit via the spike on
the audio tracks. They just import the video files from the SD cards (or whatever), sync them up via the spike, and insert cuts between tracks.
NY <[email protected]> wrote:
Is film used much for TV documentaries and drama, or is it all
electronic nowadays? I've noticed that documentaries that are clearly
shot on video sometimes use separate sound recording - the modern trend
is to show a clapperboard being clapped at the beginning of interviews
while the subject is being introduced, something that was always edited
out in the days of film. Seems a bit of a retrograde step, making a
gimmick out of it.
AIUI that's also used when there are multiple cameras. eg if the presenter is doing a car review, there are multiple small cameras (GoPro or better) strapped to the car in various positions to get different angle shots. They're all recording locally, rather than being piped back anywhere.
Then they drive it down the road while chatting to the interior camera, and the edit cuts between various cameras all synced up. So when they tell us they put their foot down and we have footage of the exhaust making a noise, the editor can cut to it automatically aligned without having to do
anything.
In that instance the cheaper version of the clapperboard is to honk the
horn, which allows them to align the footage in the edit via the spike on
the audio tracks. They just import the video files from the SD cards (or whatever), sync them up via the spike, and insert cuts between tracks.
Film was also usually mag striped, meaning extreme care was necessary in handling and processing.
News footage commag was not normally shot with the intention to transfer
to sepmag. This made life difficult for everyone back at base, not least because mag is prone to shedding oxide - which can do all sorts of nasty damage to the picture area and any machines it clogs. And obviously you
need to keep magnetic fields well away.
Why commag? Speed. You cut out two processes: transfer (1/4" tape to
sepmag), and syncing-up. And editing is sort-of faster as there's only
one track. Editors _would_ get audio transfers done as needed, but 'only
one TK' was true in Bristol, and on difficult days there would be a
queue! We had no ability to playback commag in the dubbing theatre,
although we regularly ran reversal stock on the picture transport (which
had no sound head). I can't remember on which side of the film the mag stripes were (emulsion or backing), but there were two stripes - the
actual audio stripe next to the sprocket holes, and a much narrower 'balancing stripe' on the other edge, so that there was no tendency for
the stock to wind into a cone because of asymmetry. The balancing stripe wasn't used for anything, but it probably made commag Super-16 impossible.
On 12/05/2025 12:07, John Williamson wrote:
Reversal film was mainly used for news and
current affairs. As soon as they got decent
quality video recorders that could be carried
round, they stopped using it. It was no use for
serious stuff as the colour was not good and
couldn't be corrected except by adding filters
to the camera.
I imagine that the colour rendition of reversal
film (mainly Ektachrome 160 tungsten) was worse
than negative partly because they often
push-processed the film by one to two stops to
allow filming in lower light.
I've seen the results of E160 pushed 2 stops,
using 35 mm still photography. Many years ago my
sister wanted me to take some photos at a
gymnastic exhibition that she was involved in. I
knew it would be under tungsten light so I went
for E160 tungsten, pushed two stops, in preference
to E400 daylight where I'd have lost two stops in
the blue filter to match to the tungsten light.
The results were not pretty: garish colours,
burnt-out highlights, grainy as hell - rather like
your average TV news report ;-)
I've have thought that well-exposed, well-lit
reversal film was capable of good results, because
any colour cast could easily be corrected in the
telecine with the tilt-and-twist joysticks. Not as
flexible, perhaps, as photographic grading, where
different coloured filters and exposures could be
used for different shots, at the contact printing
stage.
Is film used much for TV documentaries and drama,
or is it all electronic nowadays? I've noticed
that documentaries that are clearly shot on video
sometimes use separate sound recording - the
modern trend is to show a clapperboard being
clapped at the beginning of interviews while the
subject is being introduced, something that was
always edited out in the days of film. Seems a bit
of a retrograde step, making a gimmick out of it.
On Fri, 16 May 2025 23:14:54 +0100, NY <[email protected]> wrote:
I hadn't realised that news cameras recorded sound in-camera on a mag
stripe. I thought they used a separate Nagra for sound as for all other
film work. But I can see the advantages of commag - and the HUGE
disadvantage when it comes to cutting, because of the picture-sound
offset ;-)
BBC Scotland used sep. mag. for news and current affairs shot on reversal.
So the sound recordist carried the usual Nagra recorder using clapper board/crystal sync with the camera. There wasn't any holdup back at base since the sound was transferred to mag while the film was being processed, and the editor could handle the material with no sync problems.
In fact, for very late stories it was known for the story to be cut on
sound which was normally available first, then the picture matched to
sound when it came out of processing. This required an editor who knew
what he/she was doing.
Jim.
I hadn't realised that news cameras recorded sound in-camera on a mag
stripe. I thought they used a separate Nagra for sound as for all other
film work. But I can see the advantages of commag - and the HUGE
disadvantage when it comes to cutting, because of the picture-sound
offset ;-)
If you can stand it, please check through the
other stuff wot I wrote for errors, etc.
I've done that. I was shooting a home movie video on my camcorder and I wanted a wide shot of me talking too far away for the camcorder's mike
to pick up. Rather than faffing around with radio mikes and working out
how to make the camcorder use that input instead of the one from its own mike, I recorded the sound on my mobile phone and synced them by
clapping my hands. The hardest part was making Adobe Premiere adjust the
time offset of the separate audio track so the sound of my clap matched
the video of my hands coming together.
I always wondered how they did it in the days of film. The sound tape
was usually dubbed onto separate sprocketed magnetic film base (SEPMAG)
and the picture and sound films were cut correspondingly, but that
imposes a restriction that the editor on his Steenbeck can only shift
the sound to the nearest sprocket hole ie the nearest 1/25 second. An
error of +/- 20 msec is noticeable...
I remember a 1990s drama series set in a TV newsroom, and one episode concerned a reporter reporting from an oppressive regime. The cheap
camcorder that he was given got trashed or confiscated, so the fixer in
the foreign country got the reporter a Super 8 film camera and a couple
of cartridges of Ektachrome (grain the size of footballs on a tiny Super
8 frame!) which were hastily processed and transmitted while still wet.
Was film (normally 16 mm rather than Super 8) ever telecined wet because
of tight deadlines?
On 16/05/2025 14:07, NY wrote:
[]
I always wondered how they did it in the days of film. The sound tape was
usually dubbed onto separate sprocketed magnetic film base (SEPMAG) and
the picture and sound films were cut correspondingly, but that imposes a
restriction that the editor on his Steenbeck can only shift the sound to
the nearest sprocket hole ie the nearest 1/25 second. An error of +/- 20
msec is noticeable...
Is SEPMAG run slower then? I always assumed it ran at the same speed as
film with actual pictures on it, which has several sprocket holes per
frame (in the 35mm variant anyway - did 16mm SEPMAG exist?), so more adjustable than 1/25.
On 12/05/2025 21:08, NY wrote:
[snip]
I remember a 1990s drama series set in a TV newsroom, and one episode concerned a reporter reporting from an oppressive regime. The cheap
camcorder that he was given got trashed or confiscated, so the fixer in
the foreign country got the reporter a Super 8 film camera and a couple
of cartridges of Ektachrome (grain the size of footballs on a tiny Super
8 frame!) which were hastily processed and transmitted while still wet.
I don't remember ever using Ektachrome, but Kodachrome (25ASA - actually
40 with a filter, so effectively 25) I thought always gave me results of
far better resolution than SD video. Was Ekta much worse, or is this just
the "8mm is for amateurs" prejudice again?
"J. P. Gilliver" <[email protected]> wrote in message[]
[]I don't remember ever using Ektachrome, but Kodachrome (25ASA -
actually 40 with a filter, so effectively 25) I thought always gave me
results of far better resolution than SD video. Was Ekta much worse,
or is this just the "8mm is for amateurs" prejudice again?
Most of the Super 8 film that my dad filmed of my sister and me was
probably Kodachrome 40/25 or the Fuji equivalent. I remember the Fuji
Towards the end, maybe about 1980, he tried a cassette of Ektachrome
(not sure what speed) and the grain is horrendous in comparison. It also seems to be more contrasty, with more evidence of burnt-out highlights.
I would say that Super 8 generally gives softer pictures than SD video, though video cameras may well do some edge-enhancement to make theYes, that's the impression I got, when viewing 8mm material that was
picture *look* sharper. I also wonder whether the lens in Dad's Nikon []
"J. P. Gilliver" <[email protected]> wrote in
message news:101hboe$215h6$[email protected]...
On 16/05/2025 14:07, NY wrote:
[]
I always wondered how they did it in the days
of film. The sound tape was usually dubbed onto
separate sprocketed magnetic film base (SEPMAG)
and the picture and sound films were cut
correspondingly, but that imposes a restriction
that the editor on his Steenbeck can only shift
the sound to the nearest sprocket hole ie the
nearest 1/25 second. An error of +/- 20 msec is
noticeable...
Is SEPMAG run slower then? I always assumed it
ran at the same speed as film with actual
pictures on it, which has several sprocket holes
per frame (in the 35mm variant anyway - did 16mm
SEPMAG exist?), so more adjustable than 1/25.
I was actually thinking of 16 mm, for normal TV
film inserts. But you may well be right even for
16 mm - maybe it has more than one sprocket per
frame. Ah, no.
https://en.wikipedia.org/wiki/16_mm_film shows one
perforation per frame, whether there is a single
row of perfs or one each side, and for Super 16 as
well as normal 16. So there is a potential for +/-
1/50 second errors (not 1/25 as I said before,
because the maximum error will be when the sound
film is half a frame adrift from the pictures -
any more any it will be closer to the next frame).
SEPMAG exists. I've seen a Youtube video of
someone lacing up a Steenbeck with two rolls of
film, one for the pictures and one with mag
coating for the sound, and adjusting the sync
between the two by choosing the nearest sprocket
hole and matching on a visible and audible sync
marker. That looked like a final transmission
master of a completed programme.
On Sun Jun 1 11:58:20 2025 "J. P. Gilliver" wrote:
On 16/05/2025 14:07, NY wrote:
Is SEPMAG run slower then? I always assumed it ran at the same speed as
film with actual pictures on it, which has several sprocket holes per
frame (in the 35mm variant anyway - did 16mm SEPMAG exist?), so more
adjustable than 1/25.
Definitely at the same speed .... complex systemes were dreamed up to ensure sync, including, but not limited to Rhythmostart - dubbing suites might need to lock up large numbers of mag bays
The sound options were
COMOPT
SEPMAG
COMMAG
SEPOPT (can be recorded linearly without pulldown jitter for recombination at the labs)
It's worth pointing out that broadcast and movies
diverged a bit over how sound was processed, as
movies have almost forever had an optical
soundtrack on the distribution prints. Even though
they adopted newer tech on location more rapidly
than broadcast (for sound, at least),
I believe "The Titfield Thunderbolt" was the first British film to use magnetically-recorded sound on location (filmed in 1952). There is an out-take showing a porter's trolley loaded with the two halves of a Leever-Rich recorder and a stack of car batteries, being pushed along
the platform at a fair speed by a couple of assistants, while the boom operator tries to follow an actor leaning out of the window of a
departing train.
On 26/06/2025 09:59, Liz Tuddenham wrote:
I believe "The Titfield Thunderbolt" was the first British film to use magnetically-recorded sound on location (filmed in 1952). There is an out-take showing a porter's trolley loaded with the two halves of a Leever-Rich recorder and a stack of car batteries, being pushed along
the platform at a fair speed by a couple of assistants, while the boom operator tries to follow an actor leaning out of the window of a
departing train.
So was the sound recorded on location in optical form for all previous
films?
It must have made a big difference to shooting costs if they no longer
needed to use film for the soundtrack on all the takes.
NY <[email protected]> wrote:
So was the sound recorded on location in optical form for all previous
films?
As far as I know it was - because there was no suitable alternative.
I remember (late 1960s) budget films - often Westerns - being in blue-and-white rather than black-and-white; I presume these were just
some gash cheap stock, though I don't know what it was - maybe surplus document-making film, or from the technicolor process - or was it deliberately made, being cheaper, than silver film for black-and-white?
On 26/06/2025 11:52, Liz Tuddenham wrote:
NY <[email protected]> wrote:
So was the sound recorded on location in optical form for all previous
films?
As far as I know it was - because there was no suitable alternative.
So tape recorders of good enough quality for use in films were only
available since about 1950? I hadn't realised that.
On a related matter (since you seem to know a lot about sound recording)
I've noticed that a lot of low-budget 1940s/50s black and white films,
as shown on Talking Pictures TV or even the "big five" mainstream
channels, seem to suffer from what sounds like crossover distortion
which is especially noticeable on dialogue. It leads to a raspy sound on sibilants.
Is that likely to be a badly adjusted (or dirty) light sensor in the
optical sound section of the telecine or could it have been introduced
when multiple prints were made from the master?
Are tape recorders still used for film sound (TV or cinema) nowadays, or
is sound almost universally recorded digitally to magnetic or solid-
I've noticed that a number of documentaries that are shot on video use a clapperboard - and it is operated as a clapperboard, not just as aYes, I'm sure it's stylistic; as you say, back in the days when the
visible ID of shot/take. It is often seen during the introductory shot
of an interviewee - we see them being seated and a clapperboard being operated. I suppose it is a stylistic trope that is in-fashion at the
moment; in the past it would have been edited out and some other visible
shot would have been used while the narration was doing the "we spoke to
Mr X, the world expert on the subject" introduction.
On 26/06/2025 11:52, Liz Tuddenham wrote:
NY <[email protected]> wrote:
So was the sound recorded on location in optical form for all previous
films?
As far as I know it was - because there was no suitable alternative.
So tape recorders of good enough quality for use in films were only
available since about 1950? I hadn't realised that.
On a related matter (since you seem to know a lot about sound recording)
I've noticed that a lot of low-budget 1940s/50s black and white films,
as shown on Talking Pictures TV or even the "big five" mainstream
channels, seem to suffer from what sounds like crossover distortion
which is especially noticeable on dialogue. It leads to a raspy sound on sibilants.
Is that likely to be a badly adjusted (or dirty) light sensor in the
optical sound section of the telecine or could it have been introduced
when multiple prints were made from the master?
Are tape recorders still used for film sound (TV or cinema) nowadays
or
is sound almost universally recorded digitally to magnetic or
solid-state disk?
I noticed when I went to watch scenes of Lewis
(Inspector Morse spin-off) being filmed in 2005-7, that clapperboards
were not always used and there was no cable link from the camera to the
sound recordist. Maybe there was a wifi link that kept the film camera
in sync with the sound recording equipment of whatever technology was
being used, and uniquely tied each frame of film to the corresponding recording timestamp and identified take and shot numbers.
I've noticed that a number of documentaries that are shot on video use a clapperboard - and it is operated as a clapperboard, not just as a
visible ID of shot/take. It is often seen during the introductory shot
of an interviewee - we see them being seated and a clapperboard being operated. I suppose it is a stylistic trope that is in-fashion at the
moment; in the past it would have been edited out and some other visible
shot would have been used while the narration was doing the "we spoke to
Mr X, the world expert on the subject" introduction.
NY <[email protected]> wrote:
The tape recorder was invented a long time ago - even before electronic amplifiers were available to raise the playback signal to a useable
level.
When amplifiers became available the biggest problem was high
background noise level and distortion. In effect the magnetic domains exhibited 'stiction' and didn't respond linearly to the magnetic field applied during recording. To overcome this, the tape was pre-magnetised
and then brought back from saturation during the recording process.
This resulted in only a small proportion of the available magnetism
being available in a linear way.
The stiction was overcome by applying a high-frequency bias during
recording. This was too high a frequency to be recorded on the tape but
it 'joggled' the magnetic domains so that they responded smoothly to the audio waveform over a wide amplitude range. It was invented at least
three times (once by accident due to an unstable recording amplifier)
but only started to be applied in a serious manner during WWII by the Germans. They invented a series of broadcast and military recorders
which used coated and uncoated plastic tape. (One used spinning heads
to speed up or slow down the playback.)
At the end of the war, the technology was captured by the Allies and developed into the tape recorder as we now know it. The quality wasn't initially all that good but it was gradually improved until, by the
early 1950s, it was considered good enough to use professionally. The
BBC 'D' disc recorder could still out-perform any tape recorder until
Dolby and CDs came along, but the recordings were more expensisve and
wore out quicker.
I don't have a television set, so I can't be specific, but there were
many, many causes of distortion at every stage of the process. What you
have described sounds like noise-gating, where the soundtrack was
pinched to black when the sound became faint, so as to prevent a lot of background noise from dirty and scratched copies.
I've noticed that a number of documentaries that are shot on video use a
clapperboard - and it is operated as a clapperboard, not just as a
visible ID of shot/take. It is often seen during the introductory shot
of an interviewee - we see them being seated and a clapperboard being
operated. I suppose it is a stylistic trope that is in-fashion at the
moment; in the past it would have been edited out and some other visible
shot would have been used while the narration was doing the "we spoke to
Mr X, the world expert on the subject" introduction.
Fashion gets everywhere.
J. P. Gilliver <[email protected]> wrote:
[...]
I remember (late 1960s) budget films - often Westerns - being in
blue-and-white rather than black-and-white; I presume these were just
some gash cheap stock, though I don't know what it was - maybe surplus
document-making film, or from the technicolor process - or was it
deliberately made, being cheaper, than silver film for black-and-white?
Sounds like the Diazo process, which was very cheap but I didn't think
it was ever used for cinematographic film (it was used for the Ozophane
sound recordings). Could the colour have been something to do with the projection lamp, the projectionist using up the dying hours of a worn
out high-pressure mercury lamp or a set of dud carbons for a
non-critical audience?
I didn't know about pre-magnetised tapes. I knew about DC permanent
magnet bias in the tape recorder as a forerunner of HF AC bias. I
believe some very cheap consumer tape recorders used DC bias well into
the 1960s.
NY <[email protected]> wrote:
[...]
I didn't know about pre-magnetised tapes. I knew about DC permanent
magnet bias in the tape recorder as a forerunner of HF AC bias. I
believe some very cheap consumer tape recorders used DC bias well into
the 1960s.
That was what i meant: the tapes weren't sold as pre-magnetised, they
were magnetised just before the recording head by a permanent magnet (or
an electromagnet in earlier machines).
J. P. Gilliver <[email protected]> wrote:
[...]
I remember (late 1960s) budget films - often Westerns - being in
blue-and-white rather than black-and-white; I presume these were just
some gash cheap stock, though I don't know what it was - maybe surplus
document-making film, or from the technicolor process - or was it
deliberately made, being cheaper, than silver film for black-and-white?
Sounds like the Diazo process, which was very cheap but I didn't think
it was ever used for cinematographic film (it was used for the Ozophane
sound recrdings). Could the colour have been something to do with the projection lamp, the projectionist using up the dying hours of a worn
out high-pressure mercury lamp or a set of dud carbons for a
non-critical audience?
I've noticed that quite a few of the B&W films shown on Talking Pictures
have a faint magenta or olive green cast, which suggests that someone
hasn't killed the colour and mapped the original telecine output to
R=G=B greyscale. Sometimes you even see a change within the same film,
maybe from one reel to another.
NY <[email protected]> wrote:
[...]
I didn't know about pre-magnetised tapes. I knew about DC permanent
magnet bias in the tape recorder as a forerunner of HF AC bias. I
believe some very cheap consumer tape recorders used DC bias well into
the 1960s.
That was what i meant: the tapes weren't sold as pre-magnetised, they
were magnetised just before the recording head by a permanent magnet (or
an electromagnet in earlier machines).
I presume AC bias works a bit like amplitude modulation, with the audio frequency AMing the bias frequency carrier; and the unmodulated
amplitude takes the magnetism into the linear position of its hysteresis curve.
I used to have an Akai X-IV portable tape recorder
that had three heads, One erase head, one bias
head which contacted the back of the tape and the
third for the audio signal, which was used for
playback and record.
In its day, it was among the best quality
recorders available, as there was no electrical
interaction between the bias signal and the audio
signal.
On 26/06/2025 19:46, John Williamson wrote:
I used to have an Akai X-IV portable tape recorder that had three
heads, One erase head, one bias head which contacted the back of the
tape and the third for the audio signal, which was used for playback
and record.
In its day, it was among the best quality recorders available, as
there was no electrical interaction between the bias signal and the
audio signal.
Crossfield bias?
I think it had other issues, although I can't remember what... and
Jorgensen is on a bookshelf downstairs.
To change the subject slightly, Nagras use a quite low bias frequency. I think it's only a bit more than 30kHz. You can hear it quite clearly if
you slow a Nagra-recorded tape down.
I gather that the B&W output of the ZX81 cut a lot of corners with the
timing of the signal and this meant that some TVs couldn't display ZX81
output. I think it was because there wasn't a half-line vertical spacing
between the odd and even fields. This reference
Wasn't it thus 312/50 rather than 526/25?
I presume for video recorders, the bias frequency still needs to be >significantly higher than the signal frequency, which means *well* over
5 MHz which is the upper limit of an analogue 625/25 video signal.
Nominally 6 MHz for a system I, I think. But - I think for all formats -
the raw video isn't recorded, it's FMd (onto quite a low carrier for
domestic VCRs, but then they only manage about 2� [VHS] 3 [Beta & V2000] >MHz), so I don't know if a bias signal was needed; I don't think the
FM'd carrier needed to be _linwarly_ recorded, only its frequency
recovered.
I presume AC bias works a bit like amplitude modulation, with the audio >frequency AMing the bias frequency carrier; and the unmodulated
amplitude takes the magnetism into the linear position of its hysteresis
On 2025/6/26 22:50:35, NY wrote:You are correct. As domestic video recorders used FM modulation for the
[]
How does the bias frequency affect the quality of the recording -
assuming you don't slow the recording enough to put the bias frequency
into the audible range ;-)
(No idea: presumably lower is easier in that the head will more easily
convey it, at the risk of perhaps it - or more likely heterodyne
products - being audible?)>
Is it a case of lowest is best or highest is best? Nagra must have hadIt hadn't occurred to me that it might actually get recorded, since it
a reason for using a low frequency. https://en.wikipedia.org/wiki/
Tape_bias says that typical bias frequency is 40-150 kHz.
was normally _so much_ higher.
I remember at school, when I first looked at my portable Philips that
ran on 7½ volts of C cells with one of the school oscilloscopes, being surprised that IIRR about 50V of bias oscillation was there.>
I presume for video recorders, the bias frequency still needs to beNominally 6 MHz for a system I, I think. But - I think for all formats -
significantly higher than the signal frequency, which means *well*
over 5 MHz which is the upper limit of an analogue 625/25 video signal.
the raw video isn't recorded, it's FMd (onto quite a low carrier for
domestic VCRs, but then they only manage about 2½ [VHS] 3 [Beta & V2000] MHz), so I don't know if a bias signal was needed; I don't think the
FM'd carrier needed to be _linwarly_ recorded, only its frequency
recovered. Hifi sound likewise used a couple (for stereo) of carrier frequencies - lower. I guess the _linear_ audio track would have needed
bias, though, especially as it was narrow and a slow tape speed too.
(There were even some linear stereo - so _very_ narrow tracks.)
I remember reading - I think - that the reason for the use of the FM
carrier was that a tape recording system can only handle a certain
number of octaves (8 I think), and as video includes very low
frequencies (ideally, DC!), it had to be FMd to keep such a range. I
don't know what truth there is in this, but it made sense to me at the
time: we all realise that the highest frequency recordable is limited by
the head gap/tape speed combination, but I guess there's a practical
lower limit caused by the amount of an LF signal you can impress on the
tape.
On 26/06/2025 22:25, SimonM wrote:
On 26/06/2025 19:46, John Williamson wrote:
I used to have an Akai X-IV portable tape recorder that had three
heads, One erase head, one bias head which contacted the back of
the tape and the third for the audio signal, which was used for
playback and record.
In its day, it was among the best quality recorders available, as
there was no electrical interaction between the bias signal and
the audio signal.
Crossfield bias?
I think it had other issues, although I can't remember what... and Jorgensen is on a bookshelf downstairs.
To change the subject slightly, Nagras use a quite low bias
frequency. I think it's only a bit more than 30kHz. You can hear
it quite clearly if you slow a Nagra-recorded tape down.
How does the bias frequency affect the quality of the recording -
assuming you don't slow the recording enough to put the bias
frequency into the audible range ;-)
Is it a case of lowest is best or highest is best? Nagra must have
had a reason for using a low frequency. https://en.wikipedia.org/wiki/Tape_bias says that typical bias
frequency is 40-150 kHz.
I presume for video recorders, the bias frequency still needs to be significantly higher than the signal frequency, which means well over
5 MHz which is the upper limit of an analogue 625/25 video signal.
Professional videotape systems recorded the entire signal directly,
and frequency modulated a carrier, about 5-10Mhz I think.
What, they record _both_ the raw video _and_ an FMd version of it? (If
so, why?)>
The advantage is that you don't get any loss of quality from
separating the chrominance and luminance signals, but you do have to
do something about random phase jitter resulting from mechanical
imprecision of the machinery. This gives colour subcarrier phase
errors vastly greater than the one degree or so required for reliable
decoding, so requires electronic buffering - a timebase corrector - to
iron out the variations.
This would perhaps also relate to the 8 (frame? field?) block size I've >sometimes seen referred to, for full broadcast-quality reproduction of >PAL-encoded video.>
How does the bias frequency affect the quality of
the recording - assuming you don't slow the
recording enough to put the bias frequency into
the audible range ;-)
Is it a case of lowest is best or highest is best?
Nagra must have had a reason for using a low
frequency. https://en.wikipedia.org/wiki/Tape_bias
says that typical bias frequency is 40-150 kHz.
I presume for video recorders, the bias frequency
still needs to be significantly higher than the
signal frequency, which means *well* over 5 MHz
which is the upper limit of an analogue 625/25
video signal.
The Nagra III bias frequency was 60kHZ, the Nagra IV was 120kHz.
I was a Nagra service enginer from '69 to '74.
I gather that the B&W output of the ZX81 cut a lot of corners with the
timing of the signal and this meant that some TVs couldn't display ZX81 output. I think it was because there wasn't a half-line vertical spacing between the odd and even fields. This reference
<http://www.fruitcake.plus.com/Sinclair/ZX81/Chroma/ChromaInterface_PictureImprovement.htm>
doesn't mention that but does mention the lack of a back porch for
clamping of the black level - a naive omission ;-)
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