405 line system - aspect ratio & pedestal?
Ed Ellers
"Was the aspect ratio on 405 always 4:3, or did it start off being 5:4?"
I'm told it was 5:4 until 1950.
"Also, I remember being told at Evesham (BBC Training Dept.) in 1963 that
there used to be a pedestal in the 405 line waveform that set the black
level a few % above the top of syncs. I recall this may have been
5%.......... It was apparently removed shortly before the Coronation in
1953 - does anyone have any knowledge of this?"
I've read this as well, but haven't seen any details. American broadcasters
were inserting "setup" intervals of various percentages around the same
time, so when the NTSC color system was standardized in 1953 it included a
7.5% setup interval that also applied to monochrome transmission. This is
still part of the standard and is still used in most countries that use NTSC
(Japan uses zero setup, as is used for PAL and SECAM).
"I am also interested to hear from people with memories of 405 NTSC colour
from AP and Studio H LG."
Me too! (Weren't the later Studio H originations on 625 lines, briefly in
NTSC and later in PAL?)
db
BBC may have used the facilities at Studio H for 625 PAL training. I
remember seeing the 405 line TX's, mainly documentary films, on a monochrome
receiver. They were covered in subcarrier moiré! I'd love to get hold of a
system spec. for 405 NTSC.
The cameras were Marconi 3 x 3" IO ( a badge engineered RCA TK41 I believe)
and these were also used by Intertel (and others) in the late '60's in the
525 line mode. About a six hour line-up period to stabilise and of course
anything you tweaked knocked out the registration! Valve coders too! These
cameras were replaced at Intertel and elsewhere with Philips PC60 (3
Plumbicon).
John Burgess
Roger Wilmut
<davidb...@yahoo.co.uk> wrote:
> Hello,
> Was the aspect ratio on 405 always 4:3, or did it start off being 5:4?
> Also, I remember being told at Evesham (BBC Training Dept.) in 1963 that
> there used to be a pedestal in the 405 line waveform that set the black
> level a few % above the top of syncs. I recall this may have been
> 5%.......... It was apparently removed shortly before the Coronation in
> June
> 1953 - does anyone have any knowledge of this?
> I am also interested to hear from people with memories of 405 NTSC colour
> from AP and Studio H LG.
> Many thanks,
> John Burgess
>
>
I have a useful book called 'Television Up-To-Date', by R.W.Hutchinson,
published in 1935, second edition 1937. It gives full details of the
initial Baird and EMI systems (referring to 180-lines as high
definition) but at the end it describes the high-definition 405-line EMI
system that was then being tested in alternation with the improved Baird
system. (Apparently both companies has also done tests up to 700 lines
in the lab).
I quote: 'Baird's picture-ratio follows the custom of the cinema, viz.
4:3 (after allowing for synchronizing pulses, etc.). The EMI system
differs slightly from this, being in fact 5:4. Maird's picture width is
therefore 1.33 times its height, as at the theatre, and EMI's width is
1.25 times the height.'
The book also shows the line waveform, with black level being at 30 per
cent, stating that slight variations were allowable.
When television reopened after the war the same EMI standard was used (
it's a pity they didn't go for more lines then, but they were concerned
about existing set owners - a bit silly, since these were in the
hundreds, and the sets had been gathering dust for six years), with the
5:4 aspect ratio (the 10-line switching blank being additional).
On 3 April 1950 it was changed to 4:3 (information from 'BBC Engineering
1922-1972' by Edward Pawley), presumably by blanking the top handful of
lines (which would have been overscanned on most sets anyway).
--
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remove the nospam to reply (but you knew that already)
Stephen
"db" <davidb...@yahoo.co.uk> wrote in message
news:aivp80$26m$1...@paris.btinternet.com...
> Hello,
> Was the aspect ratio on 405 always 4:3, or did it start off being 5:4?
> Also, I remember being told at Evesham (BBC Training Dept.) in 1963 that
> there used to be a pedestal in the 405 line waveform that set the black
> level a few % above the top of syncs. I recall this may have been
> 5%.......... It was apparently removed shortly before the Coronation in
June
> 1953 - does anyone have any knowledge of this?
> I am also interested to hear from people with memories of 405 NTSC colour
> from AP and Studio H LG.
> Many thanks,
> John Burgess
I made some photocopies from an old colour television text book which was
based on 405 NTSC Colour in Wood Norton library last year. It says the
subcarrier frequency was 525/2 times line frequency or 2.6578125 Mc/s. The
book is "Colour Television NTSC System, Principles and Practise" by
P.S.Carnt and G.B.Townsend, Illiffe Books (1961).
I'm constructing a web page about 405 Colour at
http://www.sptv.demon.co.uk/405colour
Stephen Peterson
NTSC RCA studio Monitors! Apparently my then boss worked at studio H LG and
had somehow liberated the old monitors! These were huge- all valve with a
round tube! My boss told me that many programes were made in 405 colour
including the Billy Cotton Band show and the Black and white Ministals! Of
course the Great British public knew nothing of these developments!
Apparently he told me that VERA could record colour but no one had the
chance to try it!
"Stephen" <ste...@junkmailblocker.sptv.demon.co.uk> wrote in message
news:1029133478.13100....@news.demon.co.uk...
Richard Lamont
> In article <aivp80$26m$1...@paris.btinternet.com>, "db"
> <davidb...@yahoo.co.uk> wrote:
>
>> Was the aspect ratio on 405 always 4:3, or did it start off being 5:4?
>
> On 3 April 1950 it was changed to 4:3 (information from 'BBC Engineering
> 1922-1972' by Edward Pawley), presumably by blanking the top handful of
> lines (which would have been overscanned on most sets anyway).
I don't think the number of active lines, or any other parameter, was
changed. They changed the aspect ratio by - wait for it - tweaking the
width and height controls on the receiver! (And the equivalent at the
camera etc.)
--
Richard Lamont
ric...@stonix.demon.co.uk