Baird Television Limited

[Panrock]

Not sure how to quote more than one person in just one post. Anyway:


Peter wrote:  Did I calculate correctly in suggesting the scanning disc curvature would be less than 3 line widths for the 240 line picture?

Maybe for a full 240-hole disk, but for a 60-hole one (allowing through more light and a larger frame) I make the curvature to be over 8 lines. See attached. Check any 'maths' from me carefully. It's often wrong. Do you know the actual hole count and size of the 'film' disk?


Mark wrote: Was your ZIP file was within the size limit? If not, could you try a smaller one, just to be sure there's nothing wrong with the settings for your account.

My file was OK for size then. If you see it here, then my second try has succeeded. Thanks by the way for looking into this.


Jeffrey wrote: Steve, I remember that production only too well. I don't know how much of your advice they took. 

You're being diplomatic.   Virtually zilch i should think.


Steve

[ppppenguin]

For me, some good things came from that production. Some of it was fun. I got to meet the irrepressible Lily, who had danced on TV in 1937. I also met Professor Danielle Goerge who presented the M-EMI side. Superb engineer and lovely person. I've met her several times since at IET Savoy Place. She will be IET President for a year from this October. Paul Marshall came down with his re-created CPS Emitron camera - the nearest working camera to a pre-war Emitron that was feasible. You can't just run up a new Emitron like you can a scanner disc.

I even appeared in shot for a few seconds, though not sure that was a good thing. Hugh Hunt's students were a great bunch, obviously talented engineers and pleasure to meet. I wasn't expecting a fee but I didn't even get any form of credit. Nor did Paul Marshall and others who had helped.

[peter scott]

Hi Steve, Your calculation is much more rigorous than mine was. It took me a while to follow your working but I'm now convinced and agree your 8.3 lines. So a distortion of 3.5%. I would have thought that might be noticeable of some images.

I've updated my web page.

Many thanks,

Peter

[peter scott]

Here's a 240 line TCC and the red box has height of 8 lines!

   

Peter.

[ppppenguin]

I would have expected 8 lines of distortion to be visible on a test pattern. Especially the way Peter has shown it.

I've seen 240/25 on a pre-war TV and also on a modern-ish monitor. The picture looks fine but the flicker is horrible. The video BW of a 240/25 signal is about half that of a 405/50i signal. This gave the entire video chain from camera to CRT a much easier job. Pictures tend to look sharp. 3MHz or so BW was possible then but not easy. Also 405/50i gave 405 lines only on still pictures. As soon as anything moves the effective vertical resolution drops to 202 lines. This is ignoring aperture effects and Kell factor.

The problem was that 240/25 was really pushing things with mechanical scanning, apart possibly from the telecine. I'm sure Baird himself and BTL (JLB was no longer directly involved by then) that mechanical scanning had run out of steam, hence their work with the Farnsworth "electron camera". Also all receivers except Scophony were fully electronic, again bowing to the inevitable. 240/25 as a standard gave no headroom for improved kit to give better pictures. 405 amply demonstrated that it could benefit from newer technology.