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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 27th Mar 2020, 7:36 pm   #61
Heatercathodeshort
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Default Re: 1946 Why 405 lines?

Picture taken this afternoon on a 17" Murphy V310, probably one of the best 405 line receivers of the mid 50's period.
The off screen shot does not do justice to the superb picture that sports 100% interlace. It is pin sharp with a high level of usable contrast making it difficult to resolve at full speed with digital cameras. The original Mazda CRM172 aluminised tube certainly gives a good account of itself. One of the better Mazda CRTs.
This service area model does not incorporate vision AGC, gain being controlled via two preset sensitivity controls. One for Band 1 and one for Band 3. The DC conditions are maintained and it shows! 52 years old. Amazing. John.
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Old 27th Mar 2020, 8:01 pm   #62
Ted Kendall
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Default Re: 1946 Why 405 lines?

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rather than just the likes of Joyce Grenfell
What on earth has that got to do with it?
I feel that Joyce Grenfell wasn't qualified to sit on the panel; either technically, or as a representative of the viewing public.
I have nothing against her personally; I think she's hilarious, but that isn't exactly what the Pilkington Committee needed.
I should have thought that an articulate and experienced performer would have had something to bring to the discussion - after all, the technology is nothing without the talent. And she was formidably intelligent, to boot...
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Old 27th Mar 2020, 8:51 pm   #63
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Default Re: 1946 Why 405 lines?

The Pilkington Committee was much more than 405/635 colour TV standards although that was an important item. I was a teenager when it was in session and didnít take any notice of it, probably didnít understand the consequences of its decision either.
A short version of the report, itís about 50 pages.
https://archive.org/details/op1265876-1001/mode/2up
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Old 28th Mar 2020, 11:13 am   #64
peter_scott
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Default Re: 1946 Why 405 lines?

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It is pin sharp with a high level of usable contrast making it difficult to resolve at full speed with digital cameras. John.
It does look very good. To get the best photo image you need to cause the camera to use a long exposure (perhaps 1/5th sec) so reduce the sensitivity to 100 ASA or lower and turn the brightness and contrast on the set down really low. You will need to steady the camera on a tripod. Don't hand hold it and use the self timer so that you don't shake it by pressing the shutter. Clearly the television image needs to be frozen for this technique.

Peter

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Old 28th Mar 2020, 12:36 pm   #65
Peter.N.
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Default Re: 1946 Why 405 lines?

I agree it does look good but it would probably look a lot sharper looking at the screen. The firm I worked for before I went self employed were Bush agents and those early sets really did give a pin sharp picture.

Some CRT's were better than others and I always thought that the magnetically focused ones gave a sharper picture than the electrostatic ones, the EHT made quite a difference too, I remember a Baird 13 channel set with very high supply, the lines were like razor blades and you couldn't defocus it at any brightness level.

Bring back simplicity - please!

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Old 28th Mar 2020, 3:15 pm   #66
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Default Re: 1946 Why 405 lines?

Ideally you need a camera with a 1/50 or 1/25 shutter setting. Before my JVC DV camcoder developed an unrepairable fault that prevented me from accessing the manual settings menu, I was able to record from the screen of CRT tv's without flicker or interrupted raster. It was necesssary to use trial and error to attain the latter by turning off and on again until the camera was synched with the TV so that no line was visible part way down the frame. I used this method to record from French TV when we were at my late brother-in-law's in France to see the 1999 eclipse.

I recall managing to get reasonable results from 405 line TV in the 1960's using my Halina 35X 35mm and Ensign 120 folding cameras, whose shutter speed ranges used the older series of multiples of 1/25 sec, but the later models of most cameras use the series with 1/15, 1/30 sec etc.
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Old 28th Mar 2020, 4:51 pm   #67
peter_scott
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Default Re: 1946 Why 405 lines?

If we are talking still cameras then 1/50 or 1/25 is not very helpful because you are unlikely to get both half frames with equal brightness even with 1/25 just because of the relative phasing of the shutter release and the frame sync pulses. You need a longer exposure so that you integrate over several frames.

With cine you really need genlock to avoid aliasing effects although some cameras with digital slow shutter ability can give quite good results.

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Old 28th Mar 2020, 6:10 pm   #68
merlinmaxwell
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Default Re: 1946 Why 405 lines?

Most new digital cameras will "auto sync" to an "AC" scene, all my Panasonic Micro 4/3rd's jobs do it, you can see them syncing in the (electronic) viewfinder. Rather impressive.
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