Films in Perspecta Stereo
Mark Gulbrandsen
You can buy a decoder board from a guy in
England(mic...@calne.demon.co.uk) and build it into a self powered box
that you could use outboard from your home decoder. This board is made to
fit into any Dolby processor, is all solid state and reasonably priced(at
least it was before the stock market sank).
Mark Gulbrandsen
Steve Kraus
Mark Gulbrandsen wrote:
> You can buy a decoder board from a guy in
> England(mic...@calne.demon.co.uk) and build it into a self powered box
> that you could use outboard from your home decoder. This board is made to
> fit into any Dolby processor,
Just to clarify, it takes the place of a Cat 150 so it fits the
CP-50,55,65,100 and 200, but not the CP-45 or 500.
Speaking of the 500, could Perspecta theoretically be processed by
the DSP's of a 500? Not that anyone but Dolby could make this
happen but does anyone know if the audio processing of the 500
is reprogrammable in the field or only by changing ROMs? Before
you answer I know that digital films will periodically update
the digital software but that's just the DIGITAL sound decoding
end of things. And I know that the CONTROL software can be
updated with a PC. But what about the nitty gritty audio
processing like 2:4 decoding and EQ? Or is this hard coded into
the chips that do it?
Mark Gulbrandsen
Since there has to be a frequency to voltage conversion going on on the
solid state perspecta cards. Taking that into consideration I doubt that
the 500 would be capable of decoding perspecta at all through the use of
different software programs.
Best,
Mark
Steve Kraus
I don't follow your logic. Why must there be a frequency to voltage
conversion? That's the analog way of doing things.
(Actually it's not really frequency to voltage per se; it's the level
of the three signals, having been filtered from the rest of the audio,
which creates the voltages for the VCAs. Voltage varies with level not
with frequency. It could even be a straight rectification I suppose.
But I digress...)
A digital implementation would look at the levels of the three
frequencies and use it to adjust the levels of the three output
channels while filtering out the control signals. After summing
Lt + Rt of course. If they can do things like compare phase and
level of two signals (DSP version of 2:4 decoding) and do 1/3 octave
EQ in the DSP's I'm sure Perspecta could be done as well. It's only
a question of whether (and how) the 500 can be programmed to do so.
Steve Kraus
Mark Gulbrandsen wrote:
> Steve if you the N.S. chip that does frequency to voltage conversion you
> don't have to build any VERY COMPLEX, very steep slope filters at all. The
> origonal; filters have a slope of around -40db just a few cycles of center
> frequency. Thats why most old decoders don't work...the filters have
> drifted too much off center frequency. All you'd need is a filter to lop
> everything below 50hz as in the orig. decoders. the three tones would be
> found and decoded by the programmable F to V chips. The output would then
> drive the VCA's. Quite elementary Mr. Watson.
Doesn't a F to V conversion imply that you will get a voltage that
varies up and down as the input frequency varies or am I not
understanding what you mean? I can see where you will want a PLL
or something so as to track better over slight speed variations
rather than just filters but I don't see how an F to V helps you.
Wouldn't it just give you a voltage variation representing wow and
flutter?
Martin Hart
The term "Perspecta Stereo" is not correct. It is called "Perspecta Sound"
and may have been printed as "PerspectaSound. This can be verified by
looking at the small print on any of the MGM films that utilized the
process. I don't recall seeing the Perspecta logo on a Paramount film, but
that might mean that I just don't recall seeing it.
Marty Hart
Curator
The American WideScreen Museum Online
http://home.att.net./~m.b.hart/
Jeff Joseph
You're quite correct, of course, but studio promotional material often
incorrectly stated "Perspecta Stereo". I have some MGM trailers of the
period that have just such tags at the end.
--
Jeff Joseph
SabuCat Productions
E-mail: sab...@sabucat.com
PeterH5322
>>
I don't recall seeing the Perspecta logo on a Paramount film, but
that might mean that I just don't recall seeing it.
>>
I know of no Paramount film that credited Perspecta.
And it's generally thought that none of Hitch's Paramount films were done in
Perspecta.
It has been verified by one journalist that an original dye-transfer print of
"Vertigo" did not contain Perspecta encoding.
The only films I know of that credit Perspecta were MGM features and some of
their cartoons.
Perhaps Hitch's only VV film for MGM, "North by Northwest" was, although it
wasn't credited as such.
NBNW certainly was completed during that period when all or most of MGM's
'scope films (all or most of which had "CinemaScope" for process credit and
"Panavision" for lens credit) were Perspecta encoded, and were credited as
such.
Does anyone know of others?
Terrytoons, perhaps?
Peter.
BENNY NEWMAN
Forgive my ignorance, correct me if I'm wrong. I thought the idea of
perspecta stereo was used for theaters that couldn't afford a full blown
4/6-track stereo installation. Also, am I correct in saying that all the
titles that were credited as being in perspecta, were originally stereo
dubs to begin with. If anybody out there can clarify this, I would be
interested to know. What exactly is the interest in having a perspecta
installation, besides historical interest, over a discrete stereo
system. I would have thought that the availability of perspecta prints
was actually worse than magnetic ones. Benny Newman.
Mark Gulbrandsen
HI Benny, Most theaters that had perspecta were stereo equipped. It still
required 3 speaker systems behind the screen, and three power amps. It did
not make use of the surround channel. The decoder was pretty expensive in
its day. I remember ads in IP magazine for them, and 1500.00 comes to mind.
In 1956 dollars thats got to be about 10K or so in todays money. I heard an
original Fairchild processor that was restored by a guy at Tektronix a few
years back and it sounded quite good. There were lots of perspecta encoded
films and cartoons available from several studios back then. I'm not sure
about how many processors were built and sold though. I've had three that
were pulled out of theaters in my area in the last 15 years.
Best,
Mark Gulbrandsen
Wide Gauge
In article <641v55$j...@mtinsc05.worldnet.att.net>, "Martin Hart"
<*m.b....@worldnet.att.net> writes:
>The term "Perspecta Stereo" is not correct. It is called "Perspecta Sound"
>and may have been printed as "PerspectaSound.
It may have been printed by many parties in many ways, but I have a
replica of a trade ad from 1954 that has a graphical logo which says
"PERSPECTA STEREOPHONIC SOUND."
Scott Marshall
Wide Gauge Film and Video Monthly
http://members.aol.com/widegauge/
Wide Gauge
In article <648k6r$f9h$1...@newsd-123.bryant.webtv.net>, ROAD...@webtv.net
(BENNY NEWMAN) writes:
>What exactly is the interest in having a perspecta
>installation, besides historical interest, over a discrete stereo
>system.
Many Perspecta films were not recorded in discreet stereo. It is desirable
to screen these films in the Perspecta format for historical reasons. Last
summer's screening of "Forbidden Planet" at the Los Angeles Museum of Art
was to demonstrate Perspecta sound, and the screening of the same film at
Cal State Long Beach this Sunday in Perspecta was necessary because no
acceptable 4-track mag print was available.
Martin Hart
In article <19971111154...@ladder01.news.aol.com>,
wide...@aol.com says...
<SNIP>
>
> It may have been printed by many parties in many ways, but I have a
> replica of a trade ad from 1954 that has a graphical logo which says
> "PERSPECTA STEREOPHONIC SOUND."
>
I stand CONTRADICTED. Check the logo on the M-G-M prints.
Marty
--
Interested in the history of Wide Screen
Movies or Old Color Movie Processes? Visit
http://home.att.net/~m.b.hart
THE AMERICAN WIDESCREEN MUSEUM Online
Wide Gauge
In article <641v55$j...@mtinsc05.worldnet.att.net>, "Martin Hart"
<*m.b....@worldnet.att.net> writes:
>The term "Perspecta Stereo" is not correct. It is called "Perspecta Sound"
>and may have been printed as "PerspectaSound.
Image of the Perspecta Stereophonic Sound logo from a 1954 trade ad is at:
http://members.aol.com/widegauge/images/perspecta.gif
PeterH5322
>>
Many Perspecta films were not recorded in discreet stereo.
>>
I'd go a little further than that.
I'd say that most Perspecta films were not recorded in discrete stereo.
Certainly none of Paramount's VV films were.
And I'd guess that most of MGM's films and cartoons which were credited to
Perspecta were also not recorded in discrete stereo.
PeterH5322
>>
Image of the Perspecta Stereophonic Sound logo from a 1954 trade ad is at:
http://members.aol.com/widegauge/images/perspecta.gif
>>
No Perspecta-encoded film I am familiar with ever used that logo.
Wide Gauge
In article <MPG.ed2abbd2...@netnews.worldnet.att.net>,
m.b....@worldnet.att.net (Martin Hart) writes:
>I stand CONTRADICTED. Check the logo on the M-G-M prints.
It is likely that Perspecta's promise evolved over the years because they
were thrown to the mat for claiming to be "stereophonic."
For what it's worth, I have:
- A copy of the 1954 Fairchild Perspecta projectionist's manual, which is
entitled "The Perspecta Stereophonic Sound Integrator." Interestingly, it
says "under license from Perspect-A-Sound, Inc."
- A copy of a chapter from a book called "Motion Picture Projection"
(1954) that calls it "Perspecta Sound" but occasionally refers to it as
stereo in phrasing for example: "the Integrator will switch from
stereophonic reproduction to center horn reproduction if..."
- A copy of the article from Journal of SMPTE (April 1955 pg 184-189)
entitled "Advantages, Scope and Limitations of the Prespecta Stereophonic
System."
- A frame from a 1950s movie with the "Perspecta Stereophonic Sound" logo
supered on screen. Image reproduced at:
http://members.aol.com/widegauge/images/pstereo.jpg
You guess the movie.
Martin Hart
In article <19971112144...@ladder01.news.aol.com>,
wide...@aol.com says...
>
> - A frame from a 1950s movie with the "Perspecta Stereophonic Sound" logo
> supered on screen. Image reproduced at:
>
> http://members.aol.com/widegauge/images/pstereo.jpg
>
> You guess the movie.
The image is obviously from a trailer, but I don't know the film. I
think the thing is a shameless attempt to fool the audience into
believing they are getting a multi track stereo film.
When you consider how Perspecta Sound worked, it's easy to see how it
might be impressive. Sound effects that are to come from the screen
sides would not have to fight with music or dialog to get the listener's
attention since the music and dialog couldn't be there or they'd move
with the effect. Also switching from center channel only to all three
screen channels will have a noticeable effect, mostly created by phasing
in the theater, not from any dimensional information in the soundtrack.
It's interesting to note that a simple Perspecta transfer to matrix
stereo won't work for some scenes. Going from center channel only to all
three front channels can't be done in a matrix system without the
necessity to create some actual differences between the center and side
channels.
MBH
Wide Gauge
In article <64cuv3$7...@mtinsc05.worldnet.att.net>,
m.b....@worldnet.att.net (Martin Hart) writes:
>When you consider how Perspecta Sound worked, it's easy to see how it
>might be impressive.
It IS impressive. After seeing "Forbidden Planet" in Perspecta, I can
confidently say that I'd see a good Perspecta presentation over seeing the
same film in mono any day.
<< Going from center channel only to all three front channels can't be
done in a matrix system >>
That's true, Marty. Interesting observation. Dan Sherlock noticed at FP
that they sometimes put quiet scenes' ambience in only the left and right
speakers to good effect. This would also be trouble for matrix surround.
Richard P. May
BENNY NEWMAN wrote:
>
> Forgive my ignorance, correct me if I'm wrong. I thought the idea of
> perspecta stereo was used for theaters that couldn't afford a full blown
> 4/6-track stereo installation. Also, am I correct in saying that all the
> titles that were credited as being in perspecta, were originally stereo
> dubs to begin with. If anybody out there can clarify this, I would be
> installation, besides historical interest, over a discrete stereo
> was actually worse than magnetic ones. Benny Newman.
I think you are right about the use of Perspecta as a substitute for 4
track mag in early CinemaScope films, but there were a great many
features (about 100 at MGM alone) and some cartoons and shorts which
were mono, but released Perspecta to utilize and exploit the gimmick
when stereo was new. Several reissues (GONE WITH THE WIND in 1954,
LITTLE WOMEN, and maybe others used Perspecta)
Agreed, the only interest today is for the revival theaters that would
be able to make use of the tracks on these 1954-1958 releases. Unlike
the mag prints, the optical tracks with Perspecta tones are still usable
and require no special processing.
R.P. May
Charles Slater
It continued being used into the early 1960s some by Japanese film makers.
Mutley
here. Must be the first new I've seen for a bout two years.. Used to
be a great news group back in the day..
Film buff Morgan
https://youtu.be/x9lrqByzdwo?t=173 Attribution is made at the end of this trailer.