[opendtv] Re: HD vs. 625 vs. 525 vs. 405

I never said the 405 was non-interlaced. I watched it as well on my Pye 12" 
receiver.

Kell worked on interlaced and non-interlaced systems. He was publishing 
papers in the early forties citing a Kell factor between 0.7 and 0.8 when 
progressive scanning was considered extinct.

Terry Harvey



At 01:20 PM 8/28/2004 +0100, Alan Roberts wrote:
>I don't like spoiling a good story, but there are mistakes in this one.
>
>ITU standard A (405-line) was interlaced. Line frequency 10,125Hz and 25Hz
>frame rate, makes it interlaced. (I know it was interlaced, I watched it for
>years and frequently had to repair and tweak our old 12" Marconiphone tv
>set). Incidentally, the strange line frequency meant that total line
>duration was 98.765,432,1 microseconds, exactly. I don't know if that fact
>was crucial in setting up the standard, I suspect that the easy relationship
>between line and field rate had much to do with it since line counters used
>valve amplifiers at that time.
>
>The earlier competitor for standard A, from Baird, was 240-line progressive
>at 50Hz. The bandwidth requirements were similar. The fight-out between
>Baird and EMI to set the UK standard before the war must have been an
>interesting time, since there were neither cameras nor displays that could
>do full justice to 405, but 240 was easy.
>
>The Kell factor is nothing to do with interlace, it's to do with sampling.
>Kell worked on progressive sampling, not interlace. The "interlace factor"
>happens to have approximately the same value for most purposes, but is a
>separate issue.
>
>----- Original Message -----
>From: "Terry Harvey" <tjharvey@xxxxxxx>
>To: <opendtv@xxxxxxxxxxxxx>; <opendtv@xxxxxxxxxxxxx>
>Sent: Saturday, August 28, 2004 2:46 AM
>Subject: [opendtv] Re: HD vs. 625 vs. 525 vs. 405
>
>
> > I would like to share a few thoughts on quality perception of broadcast
> > television.
> >
> > The 405 system (System A) produced subjectively sharper pictures due to a
> > number of factors. The original transmissions from London (until 1956)
>were
> > double sideband (instead of vestigial sideband for all other systems
> > since). This would lead to somewhat better video phase response due to the
> > presence of both sidebands. Also, the Kell factor was 1.0 instead of 0.6
> > for 525 systems. This lead to better horizontal resolution. I was
>impressed
> > with off-air 405 years ago: the pictures looked good to the critical eye.
> >
> > The move to vestigial sideband and Kell factor of 0.6 were motivated by
>the
> > need to reduce transmission bandwidth. Like interlaced scanning and
> > interleaved analog quadrature modulated chrominance systems (NTSC and PAL
> > color), the analog bandwidth reduction methods were crude but of great
> > benefit in the days before digital television signal processing became
> > available. I constantly find amusement in the fact that we in the TV
> > business still rely on these bygone methods and technology.
> >
> > I mentioned earlier that the BBC no longer accepts PAL format tapes for
> > transmission.  The move is slow in the US to abandon NTSC production and
> > delivery and I feel this is slowing down the DTV transition in this
> > country.  Broadcasters and service providers are going to have to go the
> > extra mile to ensure that production and delivery is cleaned up.
> >
> > Also, the public perception of HDTV is curious after experiencing the
> > following incident. I was in a large major television showroom only last
> > weekend and was pleasantly surprised to see an 'Olympics DTV' display.
> > However, upon closer investigation, I discovered the 61" Wega display
> > costing retail $19,000 was displaying the HD Olympics from our local NBC
> > affiliate off-the-air with noticeable NTSC chroma crawl. I questioned the
> > Sales Manager. He insisted it was HD....he pointed to a DTV set top box
>and
> > to the big display.
> >
> > I pointed out to him that the display was connected via the composite NTSC
> > interface: I helped him set it set up and the difference was dramatic. It
> > was like this for a week with the NTSC interface and why nobody noticed
> > escapes me.
> >
> > Bravo to Sinclair for taking the lead as a broadcaster promoting over the
> > air DTV.  However, more consumer education is definitely required.
> >
> > Regards,
> >
> > Terry Harvey
> > --------------------------------------------------------------------------
>----
> >
> > At 06:32 PM 8/27/2004 -0400, Mark Schubin wrote:
> > >Having just returned from a shoot in New Zealand, I thought I'd throw my
> > >two cents in on this.
> > >
> > >Back in the early 1950s, a U.S. delegation toured UK TV facilities to
> > >try to determine why UK pictures looked better.  At the time, the UK was
> > >405 lines, not 625, but it was still said to have better pictures.  The
> > >delegation determined it was because the UK equipment was better
> > >maintained -- clean lenses, etc.
> > >
> > >I found the same in New Zealand.  The equipment was in impeccable shape.
> > >
> > >Food for thought:
> > >
> > >- The resolution of human vision tops out at about 30 cycles per degree,
> > >nominally about 22.
> > >
> > >- U.S. viewers sit about 9 feet from their TV sets (the Lechner
>distance).
> > >
> > >- Those two facts combine to make it impossible for viewers to see more
> > >than 480 lines on a 25-inch 4:3 TV at normal viewing distance.  If it's
> > >22 cpd and 16:9, it's no more than 480 lines on a 42-inch set.
> > >
> > >- Meanwhile, because the psychological sensation of "sharpness" is
> > >proportional to the square of the area under an MTF curve and the use of
> > >HD in production leads to a higher MTF curve at all detail resolutions,
> > >a viewer watching a non-HD set will nevertheless see an improvement in
> > >sharpness from HD-shot programming.
> > >
> > >TTFN,
> > >Mark
> > >
> > >
> > >
> > >
> > >
> > >----------------------------------------------------------------------
> > >You can UNSUBSCRIBE from the OpenDTV list in two ways:
> > >
> > >- Using the UNSUBSCRIBE command in your user configuration settings at
> > >FreeLists.org
> > >
> > >- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
> > >unsubscribe in the subject line.
> >
> >
> >
> >
> > ----------------------------------------------------------------------
> > You can UNSUBSCRIBE from the OpenDTV list in two ways:
> >
> > - Using the UNSUBSCRIBE command in your user configuration settings at
>FreeLists.org
> >
> > - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
>unsubscribe in the subject line.
> >
> >
>
>
>
>
>----------------------------------------------------------------------
>You can UNSUBSCRIBE from the OpenDTV list in two ways:
>
>- Using the UNSUBSCRIBE command in your user configuration settings at 
>FreeLists.org
>
>- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
>unsubscribe in the subject line.


 
 
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:

- Using the UNSUBSCRIBE command in your user configuration settings at 
FreeLists.org 

- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word 
unsubscribe in the subject line.

Other related posts: