Colour recovery from B&W kinescope films

[Aussie Bloke]

G'day all.

A few months ago I came across an awesome article on a program Richard Russell in the UK has developed to recover PAL colour from B&W 16mm kinescope film recordings of colour programs and it's success rate has proven very good on some of the kinescopes. The articles can be seen here:
http://www.techmind.org/colrec/
http://colour-recovery.wikispaces.co...olour+recovery

Makes me wonder on the possibility of someone in USA developing a program like this to recover NTSC colour from 1950s B&W kinescopes of colour programs, now that would be really cool!

[W.B.]

I was just about to ask the same question about B&W kinnies of NTSC material. But you beat me to it. Well, somebody had to bring it up . . .

Maybe one could coordinate with Livefeed or something . . .

[NewVista]

So all this is made possible because they goofed up in the mastering process: (the chroma artifacts should have been filtered out prior to display as they can shift the correct grayscale levels)

[Joel Cairo]

As I mentioned in another thread, due to the technical nature of how color is encoded in PAL vs. NTSC, as well as differences in how the respective telerecordings for each format are created, Richard Russell's astounding program will not work with NTSC material. In order to develop a similar process for NTSC, it would be necessary (at a minimum) to re-create the original color burst signal of the kinescoped program, which is not feasible at this point in time.

- Kevin

[Sandy G]

Well, fiddle-dee-dee....(grin) Too bad, it was a neat idea, though...

[wa2ise]

Originally Posted by Joel Cairo

As I mentioned in another thread, due to the technical nature of how color is encoded in PAL vs. NTSC, as well as differences in how the respective telerecordings for each format are created, Richard Russell's astounding program will not work with NTSC material. In order to develop a similar process for NTSC, it would be necessary (at a minimum) to re-create the original color burst signal of the kinescoped program, which is not feasible at this point in time.

- Kevin

If there's an area of the picture with a constant color (in a scene, like sky) one could infer a burst. It would have to be done by hand to adjust the tint at least for every scene. Adjust until you get the faces right. Labor intensive.

Another complication for NTSC is if the CRT display in the kinescope has some horizontal nonlinearity. Which would look like a gradual shift in tint if you demodulated the photographed chroma subcarrier. But one could model such nonlinearity in the decoder program if there's say a title screen of some constant color at the beginning or end of the show. PAL is more tolerant of such phase errors, as the phasing flips from line to line. SECAM material should be immune to this, SECAM may be the easiest to recover the color here. Oh, no burst to tell U from V, but just shift the line alternation of the decoder if the colors come out weird.

Of course this is dependent on someone running the kinescope capture process not bothering to filter out the chroma subcarrier. Probably using equipment built before color TV was installed elsewhere in the station. "Oh, we'll just low pass filter the film to video converter later.".

[Joel Cairo]

Originally Posted by wa2ise

If there's an area of the picture with a constant color (in a scene, like sky) one could infer a burst. It would have to be done by hand to adjust the tint at least for every scene. Adjust until you get the faces right. Labor intensive.

Another complication for NTSC is if the CRT display in the kinescope has some horizontal nonlinearity. Which would look like a gradual shift in tint if you demodulated the photographed chroma subcarrier. But one could model such nonlinearity in the decoder program if there's say a title screen of some constant color at the beginning or end of the show. PAL is more tolerant of such phase errors, as the phasing flips from line to line. SECAM material should be immune to this, SECAM may be the easiest to recover the color here. Oh, no burst to tell U from V, but just shift the line alternation of the decoder if the colors come out weird.

Of course this is dependent on someone running the kinescope capture process not bothering to filter out the chroma subcarrier. Probably using equipment built before color TV was installed elsewhere in the station. "Oh, we'll just low pass filter the film to video converter later.".

Well, the bigger issue with NTSC kinescopes of color programs is that by and large, they are not made the same way that UK telerecordings were: which is to say from a MONOCHROME monitor source that displayed (with sufficient resolution) the fine patterning of the accidentally-included color portion of the transmission signal. It is that patterning that allows Mr. Russell's process to recreate and decode the color portion of the PAL signal.

Unfortunately, here in the US, most B&W kinescopes of color programs were shot off of COLOR monitors that had shadow masks-- which, (along with NTSC's inherently lower resolution) effectively killed any patterning due to the resultant dot-crawl artifacts and softness of the image.

-Kevin

[ceebee23]

This really is a sort of geeky magic... amazing ... and you never know what results the system will bring!

BUT re: NTSC ... let's hope somewhere ..somehow someone finds the time and original materials that just happen to have been created in the right way and somehow an NTSC variant of the software can somehow be made to work!

Like the BBC material, this is actually part of our cultural and social history we need to retrieve what we can.

[ceebee23]

The result of this work is at least one lost colour episode of Dad's Army has been recovered...

http://www.bbc.co.uk/pressoffice/pre...dadsarmy.shtml

http://www.guardian.co.uk/technology...ion-dad-s-army

I am not sure if Dad's Army was shown in the US but is a classic BBC comedy from the late 60s and early 70s about a bumbling group of "Home Guard" soldiers during WWII.

[NewVista]

Originally Posted by ceebee23

http://www.guardian.co.uk/technology...ion-dad-s-army

.

I think the Guardian is right when they say that this can not work for NTSC as due to the SC-H relationship in NTSC, the dot artifacts are neatly scrambled wheras in PAL more nasty diagonal lines can be often seen (which give clues to colors)

[newhallone]

Here is a link to the Dr.Who restoration team website with some great articles. It's amazing some of the things they can do now. And as time goes on more will be possible.

http://www.restoration-team.co.uk/

[cbenham]

Originally Posted by NewVista

I think the Guardian is right when they say that this can not work for NTSC...

Another difficulty of making this process work for NTSC kinescopes is the 3:2 PullUp necessary to capture 30 TV frames in 24 frames of film. In this sequence of events, one of the film frames is actually composed of the top half of one field and the bottom is composed of the bottom half of the next one.
Hard to re-arrange the four original TV fields back from the film so the color sequence is correct again.

[Joel Cairo]

Originally Posted by cbenham

Another difficulty of making this process work for NTSC kinescopes is the 3:2 PullUp necessary to capture 30 TV frames in 24 frames of film. In this sequence of events, one of the film frames is actually composed of the top half of one field and the bottom is composed of the bottom half of the next one.
Hard to re-arrange the four original TV fields back from the film so the color sequence is correct again.

Actually, this is pretty trivial to do-- I wish **all** of my restoration tasks were that easy...

-Kevin

[cbenham]

Originally Posted by Joel Cairo

Actually, this is pretty trivial to do-- I wish **all** of my restoration tasks were that easy... -Kevin

Where are you going to get the bottom half of that field that gets dropped and the top half of the next field [also dropped] that completes the image for that film frame? 12 fields get dropped per second. http://en.wikipedia.org/wiki/Kinescope

[Joel Cairo]

Originally Posted by cbenham

Where are you going to get the bottom half of that field that gets dropped and the top half of the next field [also dropped] that completes the image for that film frame? 12 fields get dropped per second. http://en.wikipedia.org/wiki/Kinescope

I think I know what you're getting at, but let me try to explain it this way-- the resultant kinescope film of your broadcast is going to be 24fps, rather than the 30 fps video rate of the original transmission. For each of those film frames, though, it's important to note that the exposure mechanism of the kinescope machine held the film in place until at least 2 video fields were exposed, meaning that the kinescope film image is just like any other strip of movie film: frame-based, rather than field-based.

If your question above refers to the now-missing 6 frames per second that were lost in the kinescoping process, then the answer is: they no longer exist, but also were never part of the kinescope film in the first place, so they are irrelevant to the discussion.

If your question refers to the standard 2:3 pulldown field blending that is part of making film conform to NTSC video transmission, then the answer is: all that is done when the 2:3 pulldown is created is the duplication of 1 frame in every 5, which turns one second of film (24 frames) into one second of video (30 frames). The duplicate frame is hidden by weaving its separated fields into those of the existing 4, in a standardized pattern. And today, it is indeed trivial to un-weave those fields, combine them back into frames, and then eliminate the duplicates to recover the original 24fps frames of the kinescope film.

So the short answer is: assuming the kinescope film was properly and professionally transferred, the full frames are all there-- it's just that their respective fields are slightly jumbled in places...

-Kevin