Anyone have any tube cameras?

[Superewza]

Or Thermionic Valve, if you prefer

I just recently found out about these, there's rather little about them on the internet and even less shot by them. But what i can find seems to be surprisingly good quality... when it's recorded straight through a computer that is, not (*shudder*) VHS.

I'm not sure why i'm so interested by them. I guess it's partly to do with their use on Apollo, and the fact that all of the data from it could be transmitted over radio.

I don't suppose anyone could explain what TV Lines are either?

 

[s162216]

TV lines are rather basically how a CRT tv works, a set of deflection coils or magnets 'sweep' beams of electrons from an electron gun across the fluorescent screen in 'lines' and form the picture on the screen. Obviously the more lines you have the higher the resolution. PAL/SECAM TV for instance is 625 lines and NTSC 525 lines so at transmission source the 'scene' is scanned line by line (similar to how a CMOS sensor works) by the picture tube in the camera/telecine, modulated (interlaced to save bandwidth with the effectively higher resolution) and then sent to be received on the TV where the electron gun and deflection coils recreate the lines as light where the screen fluoresces. Obviously this vastly simplified but you get the idea?

Until the introduction of the CCD and CMOS which make digital imaging possible, picture tubes were the only way to electronically record an image and it was how all TV cameras worked, not just the slow scan units on Apollo which had to subsequently be converted to TV standards with considerable loss of quality to be shown worldwide on TV. Cameras like you describe only record to the television standard though so unless you have a special 'high definition' MUSE one like was used for the analogue Japanese HD your limited to standard definition resolution.
Plus you can't really record them directly to a computer as the information is analogue not digital so a capture card with a ADC (analogue to digital converter) chip is needed.

Until the introduction of U-matic and other 'compact' magnetic tapes the only real way to record electronically was with 2" QUAD tapes, the machines were massive as were the tapes so they confined TV cameras to the studio with location work being done on film. I wouldn't knock VHS either - most news stuff and studio scenes after about 1980 when they became available is on VHS, Betacam, U-matic or similar although the professional versions were much higher quality than the consumer ones and recorded to the actual TV standard. Film was usually still used for location footage as it was higher quality.

Want a 'picture tube' camera? Simply pick up a pre 1985 camcorder, before CCD's became commercially viable they were the only way to capture an image electronically.

 

[Joenail]

TV lines are rather basically how a CRT tv works, a set of deflection coils or magnets 'sweep' beams of electrons from an electron gun across the fluorescent screen in 'lines' and form the picture on the screen. Obviously the more lines you have the higher the resolution. PAL/SECAM TV for instance is 625 lines and NTSC 525 lines so at transmission source the 'scene' is scanned line by line (similar to how a CMOS sensor works) by the picture tube in the camera/telecine, modulated (interlaced to save bandwidth with the effectively higher resolution) and then sent to be received on the TV where the electron gun and deflection coils recreate the lines as light where the screen fluoresces. Obviously this vastly simplified but you get the idea?

Until the introduction of the CCD and CMOS which make digital imaging possible, picture tubes were the only way to electronically record an image and it was how all TV cameras worked, not just the slow scan units on Apollo which had to subsequently be converted to TV standards with considerable loss of quality to be shown worldwide on TV. Cameras like you describe only record to the television standard though so unless you have a special 'high definition' MUSE one like was used for the analogue Japanese HD your limited to standard definition resolution.
Plus you can't really record them directly to a computer as the information is analogue not digital so a capture card with a ADC (analogue to digital converter) chip is needed.

Until the introduction of U-matic and other 'compact' magnetic tapes the only real way to record electronically was with 2" QUAD tapes, the machines were massive as were the tapes so they confined TV cameras to the studio with location work being done on film. I wouldn't knock VHS either - most news stuff and studio scenes after about 1980 when they became available is on VHS, Betacam, U-matic or similar although the professional versions were much higher quality than the consumer ones and recorded to the actual TV standard. Film was usually still used for location footage as it was higher quality.

Want a 'picture tube' camera? Simply pick up a pre 1985 camcorder, before CCD's became commercially viable they were the only way to capture an image electronically.

 

[AJQS]

+1, but I must admit a certain curiosity in how the hell this stuff works because it's neither film or digital, yet somehow captured images for many years.

 

[Morinaka]

I have to say i always wondered how TV worked before digital imaging thanks for the info.

OK, so a camera uses a lens to focus a scene at a film/sensor plane where it's recorded. So what you are saying is that instead of a sensor/film the cameras used to use a reverse electron gun(?) aimed at the focal plane, where it would scan the image into dots and lines. These dots and lines generate signals in the reverse electron gun (an analogue representation of the image), that can be transmitted over VHF/UHF frequencies and then interpreted by the electron gun in the back of a CRT TV?

So it's kind of like how a telephone converts sound into electrical signals with a magnetic coil in a microphone, transmitted over wires where at the other end the magnetic coil in the speaker turns the electrical signal back into sound.

 

[Superewza]

Hmm, thanks. I knew they were used for much television (mainly due to the excessive light trails on the Old Grey Whistle test ), but i think i understand...

If the camera has a video out it seems you can record straight through a PC, capture cards are usually no more than £30.

The most basic explanation i think i've heard is that the 'tubes' work in exactly the opposite way as a CRT display. In a display a beam of electrons is fired at a luminescent chemical (Phosphor), which causes it to give off light (the mechanism for this is extremely complicated, something to do with liberating photons and decay). In a tube light hits the chemical, which i don't think is enough to cause it to give off an electron, but does do something which can be scanned by another beam of electrons.

 

[s162216]

Not quite like a reverse CRT but I suppose you could think of them like that, a picture tube is essentially just a photocell or photomultiplier tube as its perhaps more correctly refereed to, which converts light into electrical signals by raising electrons to higher energy levels and is substantially amplified. This is the photoelectric effect (which was described by Albert Einstein and won him the 1905 Nobel Prize for Physics).

These electrical signals are modulated to be transmitted over radio waves (UHF nowadays for digital and the analogue PAL system, VHF for the old pre 1964 B&W 405 line service). At the TV the opposite effect occurs and electrons are swept across the screen line by line raising electrons once again and creating light. For colour systems the colour information is modulated into the existing radio wave.

The 'TV out' would just be a composite connection which allowed the broadcaster to see what was being recorded live and all a capture card does is to convert that analogue information to digital.

BTW the light trails are likely because of telerecording (i.e recording live TV/video an film) and they are a common sign to see if something is a telerecording.