19/4/20 (tonight) 10pm BBC4

[ppppenguin]

Steve, it might have been 60 lines. I really don't remember.

Thanks for the info on water jet cutting. You wouldn't want any part of your anatomy in the way!

Incidentally, the main production was at the old Hornsey Town Hall which is only a few miles from me. Also only a few miles from Ally Pally. Very convenient. I was there for 2 days. The other reason I remember that period is that I met Ruth at about the same time. More than 4 years on we're very happy about that.

The Baird "Intermediate film" sequences were shot on 16mm monochrome stock. Processed normally and added in post production. Paul Marshall's camera was running at 625/50 so no problems. It's routine to convert standard definition mateiral for HD productions.

[peter scott]

Counting the holes it does appear that the disc had 120 holes.

   

Peter

[ppppenguin]

I would not have wanted to be in the way if that disc had come sdrift while spinning. It would have made a very fine meat slicer.

The attached photo was taken at Ally Pally in November 2011 as part of the 75th anniversary of TV. Paul Marshall  (with rather more hair than he has now) is standing by his CPS Emitron camera. The same one used in the TV80 programme. There is a lot of light on the "victims".

[Panrock]

Counting the holes it does appear that the disc had 120 holes.

The  holes in that particular disc are not video holes - they are far too fat and would give a very blurry image indeed.  Instead, this looks like a 'sync hole' disc where the holes would be arranged in a circle, not a spiral.

Steve

[peter scott]

Hi Steve,

There don't appear to be any other circles or spirals on the disc. I suspect the ones in the photo are on a spiral but were not there for any other reason than to project a scanning light on the subject and any television images that we see in the program were shot from a proper camera and not from the photo cells. I suspect the face has about 60 lines.

Peter

    .    

[ppppenguin]

I saw the images from the disc scanner. I have no reason to believe they were faked for the programme. I saw Hunt's team adjusting the disc and the photomultipliers. I saw the pictures appearing on their PC via a high speed data acquisition system. I saw the VGA output converted to 625. But I was busy with my own work for the programme and didn't look at the details of the disc.

One imbalance in the programme was that Hugh Hunt presented from first hand experience and that of his team. Danielle George, while being a top class engineer, was presenting other people's material. She's a brilliant presenter (she gave the RI Xmas lectures a few years ago) and her MBE was awarded "for services to engineering through public engagement" but in the last resort she was a name and a face, not the person who did the work for the programme.

[peter scott]

It looks as if there were 120 holes in the disc and if we guess at 1500 rpm then frame rate would be 12.5 f/s. The capture PC certainly could store each frame and remove flicker but what was the item clamped between the photo cells?

   

Peter

[peter scott]

The image on the PC looks devoid of obvious line structure whereas the image that we are presented with does show line structure! This suggests to me that the line structure was as a result of post processing.

   

Peter

[Panrock]

Unlike you chaps, I haven't made a serious examination and I've forgotten most about it, but the whole thing looks rather dubious to me. ISTR their display was claimed to be 60-lines at 15 Hz. If the '120-line' sync wheel was indeed a genuine part of the apparatus, it could have run at half speed or provided two pulses per line. Jeffrey may be able to tell us how the synchronisation was actually done...

[ppppenguin]

Sorry, don't remember how the sync was done. As I said, I had a lot of my own work to do and only looked at some aspects of the mechanical scanning kit.