Kineskope frame rate

[DVtyro]

What frame rate did they use for kineskope? Wikipedia says, it was 24 fps with the shutter modified to better match 30i, if this is true I wonder why did not they use 30 fps. Just to save film? To make it compatible with projectors? I suppose in Europe they used 25 fps?

I suppose, running film at 60 fps was too expensive? Was it even technically feasible to map each field into a film frame back then?

[old_tv_nut]

Stations already had 24 fps telecines, used for regular films. These required various modifications in the projector mechanisms and light sources compared to theater projectors, depending on the particular pickup device (iconoscopes at first, vidicons later on), and might require complex or maybe impossible modifications to run at either 24 or 30. It made more sense to engineer the kinescope recorders (used in small numbers) to use 24 fps than to try to get every station using the recordings to modify or replace their telecines.

Europe did use 25 fps for kine recording. Their telecines also ran at 25 fps. It is funny to hear a U.S. film-based program broadcast in Europe at 25fps, as the actors voices go up a notch. Captain Kirk sounds noticeably different as he reads the intro to Startrek, and you do not need to hear one version immediately after the other to notice it. I got a kick out of this watching Startrek in a Swiss hotel room once.

[old_tv_nut]

Regarding recording one video field per film frame at 60 fps:

This introduces terrible problems, as the scan lines in the telecine have to match the scan lines in the kine recorder, or you get terrible moire. This means that the optics at both ends have to be completely distortion-free, the scan heights and vertical linearity must match perfectly, and so on.

The CBS Electronic Video Recording system, introduced in the late 60s/early 70s, did use 60 fps, on microfilm, but recorded a full video frame every 60th of a second using a field memory at the recording site (just barely technically feasible at the time). In addition, the master was recorded by electron beam, and the beam was wobbled up and down at 14.31818 MHz (four times NTSC color subcarrier) just enough to fill in the blank spaces between scanning lines, so there was no line pattern on the film to cause moire.

[Alex KL-1]

Very interesting info! I'm also think about and makes perfectly sense - but only when I read this. Before, I also wondered about the fps difference...

[DVtyro]

Whoa, thanks for the EVR mention. Two clicks from the wikipedia article, and I am watching this:

https://youtu.be/pB8zQWs89wU

180,000 pictures for 50 minutes is indeed 60 fps. For film tech, the cartridge size is reasonable.

[old_tv_nut]

Originally Posted by DVtyro

Whoa, thanks for the EVR mention. Two clicks from the wikipedia article, and I am watching this:

https://youtu.be/pB8zQWs89wU

180,000 pictures for 50 minutes is indeed 60 fps. For film tech, the cartridge size is reasonable.

A couple of comments:

1) The demo clip was from "Mission Impossible" and was 10 minutes out of a full episode. We got so used to/tired of it in the lab that we could quote every line. Our favorite was the evil villianess saying "Call me Riva, even the children call me that," which we would quote after the slightest hint of anyone hesitating before speaking our name.

2) I don't know why CBS used this narrator - can't recall if he was a CBS exec, but a really professional presenter would not divide his sentences into three-word phrases with pauses between them, would have a midwest accent instead of Eastern, and any stammers would have been retaken in a really professional production.

[DVtyro]

You were one of the engineers who worked on this machine?

You said it had a field memory, so it converted each field into a complete frame, basically doing what every modern TV set does, deinterlacing it into 60 fps?

[old_tv_nut]

The recording process at the film plant used a field memory to perform deinterlacing.
The player did not record and had no memory.
I worked on the player at Motorola.

[DVtyro]

PDFs on your website are a treasure trove! So, the picture was "painted" on the master film by an electronic beam. Then copies were made by optical duplication. Then the picture was be scanned by an electronic beam again and converted to TV image. It is an interesting blend of analog electronics with film tech. I applaud that 60 fps was chosen to preserve as much info as possible.

Considering how magnetic tape, HDDs, memory cards age over time, maybe it makes sense to reconsider using film for long-term storage? Actually, I think optical discs are the best for long term, but I am very afraid that soon there won't be any CD/DVD/BD readers.

For black-and-white version, have anyone thought that the second track should start at the end of the film, so it would work like a regular audio tape: play track 1 from the beginning to the end, then switch to track 2 and play in reverse. This way you would get 50 minutes of moving picture with just a small blip in the middle.

[old_tv_nut]

"Then the picture was be scanned by an electronic beam again" - in the player it was scanned by a light beam from a small "flying spot" CRT.
I think maybe you understood this but typed the wrong thing?

[old_tv_nut]

Originally Posted by DVtyro

...
For black-and-white version, have anyone thought that the second track should start at the end of the film, so it would work like a regular audio tape: play track 1 from the beginning to the end, then switch to track 2 and play in reverse. This way you would get 50 minutes of moving picture with just a small blip in the middle.

That's an interesting idea, but it would require the extra complication of reversing the vertical scan of the flying spot as well as the mechanics of the player, so I guess Dr. Goldmark and the CBS crew didn't think it was worth the trouble.

In the player the film was pulled across the scanning gate by a capstan that was just after the gate and well before the takeup reel. It seems to me that wouldn't work to push the film backwards through the gate.[I just realized that I don't know how auto-reverse audio cassette players work - have to look it up.]

Also, reversing might have caused secondary problems in recording the master. The sensitivity of the master film to the electron beam changed during the recording due to outgassing of the moisture in the film, so the exposure had to be changed gradually during the recording. CBS never got this totally under control. It was one factor that caused poor yields of good films. Doing this forward and reverse could be a further issue.

[DVtyro]

Originally Posted by old_tv_nut

"Then the picture was be scanned by an electronic beam again" - in the player it was scanned by a light beam from a small "flying spot" CRT. I think maybe you understood this but typed the wrong thing?

Um... Er... I need to read up on how flying spot scanner works

Originally Posted by old_tv_nut

I just realized that I don't know how auto-reverse audio cassette players work - have to look it up.

It has two capstans and two pinch rollers (not mentioning Nakamichi system here).

[Electronic M]

Originally Posted by DVtyro

Um... Er... I need to read up on how flying spot scanner works

It has two capstans and two pinch rollers (not mentioning Nakamichi system here).

I would imagine that if tape...er um film tension could be maintained via the reels that it could work fine with a single capstan system for autoreverse...I own a TEAC X-3R and it's later identical cousin the X-300R that are 3 motor single capstan auto reverse stereo RTR tape decks... Most other RTRs especially ones that could record in both directions (the Teac only recorded in one direction because it only 3 had heads and erase would be on the wrong side of the record head in reverse) had 2 capstans as did most autoreverse cassette decks, but there's probably a single capstan auto reverse cassette deck out there too.

I don't know if there's any good videos of the B&K 1077 analyst out there but it too is a flying spot scanner....In a nutshell a magnetically deflected camera tube is always going to be significantly more complex and expensive than a CRT. A high speed light sensor that only measures the light of one fixed point is always going to be cheaper than a camera even if it needs a CRT display tube to be paired with it to do the scanning for it*....Which is exactly what a flying spot scanner CRT does. In a flying spot film scanner the film frame is placed over a CRT with short persistence phosphor (essentially only the point on screen that the beam of the gun is on at that instant is lit) set up to create a blank white raster...The CRT light projects through the film and since the only light at any given instant is from the specific spot on the film over the light from the CRT screen at the point the beam is at at that instant the light that passes through the film is exactly what the base band video signal looks like minus the sync (which would be added later) and a simple cheap single point photoelectric device can convert the light to electronic video.

*Heck in the late 60s Sylvania came out with the slide theater console it was a 23" color TV packaged with a full color flying spot slide scanner. It used a hidden smaller white phosphor CRT that projected through the film onto dichloric mirrors that split the light into separate R, G, and B primary color paths that each had a photoelectric device (photo multiplier tube IIRC) to convert them to electrical signals that were passed the main (color) CRT the viewer would watch.

[old_tv_nut]

In the case of the B&K, the transparency was as big as the CRT face and was held close to it, eliminating the need for a lens at that point. In the EVR player, there was a 3-inch CRT and a lens to scan the tiny film frames - it was like a low power flying spot microscope. Nevertheless, it could produce full 4 MHz bandwidth luminance.

The recording and playback of the color subcarrier was on a separate film frame next to the lumininance and was much more complex electronically (but used identical optics). It involved recording a sine wave brightness pattern of color subcarrier at 1.8 MHz (one half NTSC subcarrier frequency, making vertical stripes of varying phase and amplitude), with an added constant amplitude and phase pilot carrier stripe pattern at 900 kHz. The resulting recovered chroma bandwidth was +/- 600 kHz, better than any consumer VCR.

[Electronic M]

Originally Posted by old_tv_nut

In the case of the B&K, the transparency was as big as the CRT face and was held close to it, eliminating the need for a lens at that point. In the EVR player, there was a 3-inch CRT and a lens to scan the tiny film frames - it was like a low power flying spot microscope. Nevertheless, it could produce full 4 MHz bandwidth luminance.

The recording and playback of the color subcarrier was on a separate film frame next to the lumininance and was much more complex electronically (but used identical optics). It involved recording a sine wave brightness pattern of color subcarrier at 1.8 MHz (one half NTSC subcarrier frequency, making vertical stripes of varying phase and amplitude), with an added constant amplitude and phase pilot carrier stripe pattern at 900 kHz. The resulting recovered chroma bandwidth was +/- 600 kHz, better than any consumer VCR.

I figured there was a lense, pretty sure my slide theater has one as well, but didn't want to overcomplicate the basic concept explaining a flying spot scanner.

The color specs of the system are quite interesting.