Behind the scenes UK experimental colour transmission 1957
 

G'day all.

Just found this amazing footage on YouTube:
http://www.youtube.com/watch?v=ub3mtKMw-q0

This clip shows the behind scenes of the experimental UK colour broadcast from January 1957 which the cameras and control room and equipment can be seen in their full glory! :)

Also (I guess this would of been posted previously) the program itself exists in it's entirety on B&W kinescope and can be viewed on YouTube as well:
Part 1: http://www.youtube.com/watch?v=b2MsQQ2UzVw
Part 2: http://www.youtube.com/watch?v=6FN9MjWXyM0
Part 3: http://www.youtube.com/watch?v=V84-5rg3i8o
Part 4: http://www.youtube.com/watch?v=jTHhyyWYW9E

noticed no one responded - just wanted to say thanks for the post

I watched 'em again....Wow...Still never have understood why color TV wasn't available in Blighty & the rest of Yoorup til so late, except for bureaucratic intransigence...And, of course, the desire on the part of some interests to tweak RCA's & America's collective nose a bit...

Maybe they waited until some of the important patents on color TV expired? :scratch2:

The UK was the first country outside the US (and Japan?) to have CTV.

Some good reasons for taking so long:
Never Twice Same Colour
Cost - at both RX and TX ends

Actually NTSC can work perfectly well with modern technology and a lot of care.

P-P-P Penguin is R-R-R Right, as long as the Diff Phase spec is good in signal path, no problem. Early B&W transmitters (used for early color) prone to this problem.

US in 1940s should have taken the advice of some (Philco) and gone with higher res (700, 800 lines) but still, 525/60 NTSC would have been a good evolution from 405/50 for England in the late 50's as well as an original system for Aust/NZ (completing NTSC for the Pacific Rim). Would have made program distribution distribution a lot easier. To hell with non-English-speaking Continental Europe, let them keep their 625/50 (frame rate too slow for good motion) and their PAL (w/ its "Hanover Blinds" & half vert chroma resolution) and they can keep their Euro currency - which England wisely rejected.

Keep in mind England was considering 405/50 NTSC not changing to 525/60. It's nearly impossible to run the frame rate of the television at a different frequency from the AC power. (at least for crt based sets) This is why all 50Hz power countries use a 50Hz field rate, and 60Hz countries use 60Hz.

Well, it was nearly impossible to do at a reasonable price with tubes at the time. Obviously eventually doable at reasonable cost with more sophisticated solid state power supplies, as demonstrated by millions of computer monitors.

You hear this now and then but I can't see how it's scientific - more an "Urban Myth".

Using systems with 25fps is unenlightened (based on 1920's 24fps film). It should not have been television spec by the 1950's.

Japan has both 50Hz and 60Hz power which must have made things a bit interesting for their TV service.

Colour made it impossible to use a mains (power line) locked field frequency. In the early days most systems relied on this to minimise the visibility of hum effects. Not sure which is more annoying; a slow moving hum bar or a 10Hz effect.

Interesting Jeff. I didn't know Japan still used mixed frequencies. Perhaps after the war everything was converted to 60Hz?

The US had a mixture of 25, 50 and 60Hz power but had mostly settled on 60Hz by the time of commercial electronic television. You can still find 50Hz based US clocks from the 20's and 30's.



Hi old_tv_nut. This is what I was referring to but you did a better job elaborating. It was certainly doable with the power supplies of the time, but not practical or cost effective. Solid state based crt monitors did eliminate the ripple effect from the power supply, but you still had to deal with stray magnetic fields that could distort and ripple the image.


This isn't quite the same comparison. 24fps film would look horrible and flicker badly if projected at 24fps. They realized this very early on and use a 2X or 3X shutter in the projector which fools the viewer into seeing 48fps or 72fps thus eliminating the flicker. Of course the content is still at 24fps so motion won't be as smooth giving it that "film" look.

It's more than power supply filtering. Watching 50Hz video under 60Hz non incandescent lighting can be bothersome due to differing flicker rates. In my office, when I watch a 50Hz/Pal feed, the screen noticeably flickers when I light the room with fluorescent lighting. With good ol' inefficient incandescent lighting, it isn't nearly as bad. I'd suspect it's probably not as bad the other way around.

I won't even touch the fact that to some 60Hz viewers, a 50Hz video source flickers no matter what, until they eventually become used to it.

I don't know what GB did in the 30's but can't see how they would achieve the necessary H/V relationship starting w/ 50hz ref. I would like to see a reference/link on this early SPG scheme.

That drove me nuts when I visited the UK and Ireland in 2000. I ended up "watching" Teletext most of the time the TV was on. Now, THAT was cool.

Visibility of flicker varies extremely strongly with absolute brightness, and varies somewhat from person to person. Some medicines can affect it. The last time I was in Europe, the TV in my room showed really visible flicker to me only on large bright areas - the average scene looked quite acceptable to me. One time (years ago) I had to use eyedrops for a few days to stop iritis (inflammation of the iris). This resulted in enhancing my flicker sensitivity to the point where I could see full modulation of the flicker from black to white on a 60 Hz NTSC display.

The colorwheel experiments done by Cliff Benham and shown at the early TV convention show that different people see different amounts of flicker at the CBS 24 frame/72 field rate, and everyone sees it on the NTSC wheel color converters.
These experiments also show clearly that it is the luminance flicker that is visible, not chrominance.

From what I've read in magazines of the period, even in the latter years of the 50's American colour television wasn't that much of a success. By success, I don't mean technically, rather the take-up of colour TV was still low, cost being an issue. Meantime, the UK and I guess Europe too were far less affluent than America so take-up here would presumably been even worse.

TTFN,
Jon

Ntsc 405
 

I think primary reason for the BBC and the UK not adopting 405 line NTSC was that the EBU had settled on 625/50 as the new European standard in the early 1950s.

This was being progressively introduced across Europe (both west and eastern Europe). (Australia adopted this standard in 1956)

France was running an 819/50 and the UK its 405 line standard both were phased out by the early 1980s.

The UK decided to introduce colour with the 625 line standard. Various investigations into the colour format were undertaken and ultimately PAL was adopted.

But the key to the decision not to proceed with 405 NTSC seems to have been cost and a fear that if they adopted 405 line NTSC colour the public would have seen less reason to adopt the spanking new 625 line standard ... because on the colour receivers of the day 405 line, 525 line and 625 line looked barely different!

I should also point out that the commercial broadcasters, especially ITN's Lord Grade were pushing heavily for colour from the moment they went on air!

The primary reason for not adopting colour on 405 line would have been that the decision was to introduce 625 line before colour was introduced and to phase out 405-line. So 405-line colour would have been pointless dead end.

The UK's adoption of PAL was almost a last minute thing. The Pilkington Comittee produced a report on the future of TV and gave a plan for the introduction of 625 line within 2 years with colour to follow on the new standard. However, the report preceeded the German PAL system (or at least its announcement in the trade press), so at the time it was almost certain that the plan was for 625-line NTSC (I say almost certain as there had also been experimental broadcasts using the SECAM system).

As to 405 and 625 not looking much different, even in the 50's some firms such as Ekco were already using a spot wobble system on their up-market sets (17"!) to try and mask the line structure and by the time of the Pilkington report early 60's screen sizes were 19" for paupers and 23" for toffs. There would definitely be a difference between 625 and 405 line colour, though in the early/mid 50's when many mono sets couldn't even fully resolve the 405 line system I accept that there 405 and 625 colour might have not shown much difference.

TTFN,
Jon

New Zealand never got colour until 1974, a year before I was born...

the really sad part..
 

the sad part of the UK not moving into colour broadcasting with 405 NTSC is that all those great programs from the early 60s from the Beeb were only made in b/w :tears:

Any SPG was a complex thing in the 1930s. Some were mechanical, like a Hammond tonewheel organ, others used lots of valves (tubes) to do frequency division. FOr 405 you start at 20250Hz. Divide by 2 to get 10125Hz for line pulses, divide by 405 for 50Hz field pulses. 405 = 3*3*3*3*5 The small numbers were essential for early frequency dividers. The 20250Hz master oscillator could be locked to 50Hz mains using a slow acting phase lock.

And many of the tapes were wiped for re-use because they were so expensive. I believe that in the US many shows were shot on film. This was rare in the UK, possibly due to the high cost.

Yes, this would be the only way I suppose. Later they would drop the mains lock as SPG's became xtal ref.

My issue remains "why 50 hz ?" [cont. next post]

My objections to these 'reasons', that you hear now and then, for 50hz countries using 25fps TV are as follows:

1. TV's (even old ones) shouldn't have AC power artifacts. If you see this, I suggest you book the set in for repair.

2. When GB designed 405/50, fluorescent lighting wasn't available*. So it's a non-sequitur to claim "50 hz was chosen to sync flicker with fluorescent lights".

3. Some countries happily enjoy 50hz pwr & 60hz TV (Chile, Japan).

4. Why is there no 12hz beat with my 72hz computer & Fluoro lights ?



*not available commercially until 1939

Keeping hum out of the entire broadcast chain wasn't easy. Hence it's a natural choice to lock field to mains.

I have gone back to the source here. Blumlein et al, The MArconi-EMI tlevision System - The Transmitted Waveform, Journal IEE 1938 p761

"Similarly with interlaced scanning the spot traverses the frame 50 times per sec, thus raising the flicker above that perceptible to the human eye......A frame frequency of the order of 50 was necessary to overcome flicker and the exact value of 50 was chosen on account of the supply frequency of this country...."

I can't be bothered to retype any more of the article but but it goes on to say that hum effects at 37.5Hz were intolerable.

Clearly at the time the decision to use 50Hz was taken it was regarded as essentially flicker free. Especially as the competition was using 25Hz. the question was could they save bandwidth by going lower than 50Hz and the answer was clearly no.

Another factor is the mains derived EHT. The filtering was terrible. The British 405 sets in our museum are powered by 60 Hz and many exhibit severe hum bars even though they are working just as they did when new.

This is not so straightforward as Jeff and the Blumlein article have pointed out. Firstly, removing ripple from the power supply to an adequate level is VERY difficult to do cost effectively using 1930/40's technology. The required amount of iron and capacitance would make the set very heavy and very expensive. The power supply on the 1936 RCA RR359 prototype sets weighs almost 100lbs by itself due to the size and number of chokes.

The problem is compounded by interlace scanning. Only a very small amount of magnetic interference is required to shift a line enough to ruin the interlace. Just having a power transformer in the set will create enough magnetic interference to show ripple in the image. Magnetically shielded transformers could be used but again are very expensive and large.

Case in point, I have a Sony 9-90UB solid state 405 line set from the 1970's and when I run it here on 60Hz power, feeding it with a 405/50i signal, the picture shows pronounced ripple and line bunching. Even when powered from a battery to eliminate the internal transformer, there is still some noticeable ripple in the image depending on where the set is placed due to stray magnetic fields at 60Hz.

Edit: I see Steve got in there while I was typing :) This is why the power supply on the RR359 is so big and heavy. They have large chokes and capacitors in the mains derived EHT to try to filter out the ripple. Hardly something that would be practical on a commercial set.

Even harder to filter at 50 Hz than 60 Hz.

---

2 video monitors side by side, one locked, the other without a signal. I've seen intereference between them on many occasions. Not with top quality kit but not everything is top quality.

I think that you need to remember that 25 frames...50 fields is actually fine ...and flicker is, certainly for most people, hardly ...if at all .. noticeable.

Afterall movie film is 24fps!

I think the key really is the 405 line seemed amazing in 1936 but by 1956 was clearly below the preferred standard.

Everyone in the industry knew colour was coming ...sooner or later.... but reality was the cost in 1955 was exorbitant both for the broadcasters and consumers.... by 1966 the situation was completely different... and the UK began colour broadcasting in 625/50/PAL in 1967/68.

Fink's Television Engineering Handbook lists the following flicker threshold luminance vs. flicker frequency (for large area flicker):

Movies 48 Hz, 20 ft-lamberts;
TV, 50 Hz, 29 ft-lamberts
TV, 60 Hz, 180 ft-lamberts

Also stated: A positive increase in flicker frequency of 12.6 Hz raises the luminance threshold ten times.

So, you can see that the visibility of flicker is strongly dependent on image brightness.

It also states that the threshold is strongly dependent on the size of the flickering area, the surround brightness, and etc.

I can see now why they were compelled to do that in those days

I found that I needed to set my CRT based 17 inch VGA monitor to 85Hz to avoid flicker. It's only moderately bright, but only 40cm from my nose. That would relate to a large area as seen by my eye.

The last post makes the point well. The peripheral vision of eye (rods) is MUCH more sensitive to large area flicker than the central zone (cones). You sit much close to a computer monitor than a TV so it subtends a much larger angle. Hence flicker is much more noticeable. That's why 60Hz on a TV is usually OK but is truly horrible on a computer monitor.

You can argue that 50Hz and 60z are not OK for HDTV because they subtend a larger angle than SDTV when used at the intended viewing distance. LCD displays inherently have no large area flicker. Other types such as plasma might well benefit from up conversion to 100/120Hz.

IIRC, I think Cuba was an early adopter of NTSC TV in 1957, IIRC. Havana had a color station before Miami did.