Colour recovery from B&W kinescope films

[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)

[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

[cbenham]

Originally Posted by Joel Cairo

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

This thread began as a discussion of the process by which B&W kinescopes made from Pal colour video could be processed electronically to recover the
color information and restore the program to full colour.

This is only possible because both the PAL video system and the kinescope camera operate at 25 frames per second. Thus each frame of the resulting B&W film includes all of the video frames and fields, and more importantly the 8 field PAL colour sequence which is the key to the colour restoration process. Without the 8 field colour sequence recovery of the original colour program can not be done

In NTSC B&W kinescopes, the 4 field color sequence is lost because 12 video fields per second are not captured in the 30 to 24 frame per second conversion process thus breaking the color sequence and making recovery of the 4 field color sequence impossible.

If the original NTSC kinescope process had used a film camera operating at 30 frames per second then recovery of the 4 field color sequence would be possible and just as in the Pal kinescope method, the 30 fps NTSC kinescopes containing all the complete frames and fields, and more importantly, the 4 field color sequence could be processed to successfully recover the color signal.

Not being able to recover the 4 field color sequence from 24 frame kinescopes is the stumbling block in NTSC.