Editing Kinescope (section)

== Technology ==

[[NTSC]] television images are [[raster scan|scanned]] at roughly {{val|60|ul=Hz}}, with two [[interlaced]] [[field (video)|fields]] per frame, displayed at 30 [[frames per second]].

A kinescope must be able to convert the 30 frame/s image to 24 frame/s, the standard sound speed of film cameras and do so in a way so that the image is clear enough to then re-broadcast by means of a [[film chain]] back to 30 frame/s.

In kinescoping an NTSC signal, 525 lines are broadcast in one frame. A 35&nbsp;mm or 16&nbsp;mm camera exposes one frame of film for every one frame of television (525 lines), and moving a new frame of film into place during the time equivalent of one field of television (131.25 lines). In the British [[405-line television system]], the French [[Analog high-definition television system#French 819-line system|819-line television system]] and the greater European [[576i|625-line television system]], television ran at 25 frames—or more correctly, 50 fields—per second, so the film camera would also be run at 25 frames per second rather than the cinematic film standard of 24 frames.

Therefore, in order to maintain successful kinescope photography, a camera must expose one frame of film for ''exactly'' 1/30th or 1/25th of a second, the time in which one frame of video is transmitted, and move to another frame of film within the small interval of 1/120th of a second.

In some instances, this was accomplished through means of an electronic shutter which cuts off the TV image at the end of every set of visible lines. Most US kinescope equipment, however, utilized a mechanical shutter, revolving at 24 revolutions per second. This shutter had a closed angle of 72° and an open angle of 288°, yielding the necessary closed time of 1/120th of a second and open time 1/30th of a second. Using this shutter, in 1 second of video (60 fields equalling 30 frames), 48 television fields (totaling to 24 frames of video) would be captured on 24 frames of film, and 12 additional fields would be omitted as the shutter closed and the film advanced.

Analog television is a field-based system, and most electronic video recording solutions retain both fields of every frame, preserving the temporal resolution of interlaced video. Some early consumer-grade video tape recorders preserved only [[Skip field|one field of each frame]]. Film, being a frame-based system, can retain full information from interlaced video by converting every field into a frame, but the required frame rate had been deemed impractical. Various solutions to the mapping problem have been developed resulting in successive improvements to the quality of the image at the traditional 24 fps frame rate. Nevertheless, video converted to film loses the fluid look of interlaced video, taking on a look somewhat similar to [[film look|film]].

=== Shutter bar and banding problems ===

The 72°/288° shutter and the systematic loss of 12 fields per second were not without side effects. In going from 30 frame/s to 24 frame/s, the camera photographed ''part'' of some fields. The juncture on the film frame where these part-fields meet is called a ''splice''.

If the timing is accurate, the splice is invisible. However, if the camera and television are out of phase, a phenomenon known as ''shutter bar'' or ''banding'' occurs. If the shutter is slow in closing, overexposure results where the partial fields join and the ''shutter bar'' takes the form of a white line. If the shutter closes too soon, underexposure takes place and the line is black. The term ''banding'' refers to the phenomenon occurring on the screen as two bars.

=== Suppressed field ===

A simpler system, less prone to breakdown, was to suppress one of the two fields in displaying the television picture. This left the time during which the second field would have been displayed for the film camera to advance the film by one frame, which proved sufficient. This method was called ''skip field'' recording.

The method had several disadvantages. In missing every other field of video, half the information of the picture was lost on such recordings. The resulting film thus consisted of fewer than 200 lines of picture information and as a result, the line structure was very apparent. The missing field information also made movement look [[Jerkiness|jerky]].

=== Stored field ===

A successful improvement on the suppressed field system was to display the image from one of the fields at a much higher intensity on the television screen during the time when the film gate was closed, and then capture the image as the second field was being displayed. By adjusting the intensity of the first field, it was possible to arrange it so that the luminosity of the phosphor had decayed to exactly match that of the second field, so that the two appeared to be at the same level and the film camera captured both.

Another technique developed by the [[BBC]], known as ''spot wobble'', involved the addition of an extremely high frequency but low voltage sine wave to the vertical deflection plate of the television screen, which changed the moving 'spot' - a circular beam of electrons by which the television picture was displayed - into an elongated oval. While this made the image slightly blurred, it removed the visible line structure (by causing adjacent lines to touch, so that no separating band of darkness lay between them) and thereby resulted in a better image. It also prevented [[moiré pattern]] from appearing when the resulting film was re-broadcast on television, which occurred if the line structure on the film recording did not precisely match the scanning lines of the electronic film scanner.

=== Moye-Mechau film recording ===

The Mechau system used a synchronized rotating mirror to display each frame of a film in sequence without the need for a [[Movie projector#Film gate and single image|gate]]. When reversed, a high-quality television monitor was set up in place of the projection screen, and unexposed film stock is run through at the point where the lamp would have been illuminating the film.<ref name="Dungate">{{cite web |url=https://www.vtoldboys.com/arthur/lgtvr.htm |title=Telerecording at Lime Grove |author=Arthur Dungate |access-date=2023-11-14}}</ref>

This procedure had the advantage of capturing both fields of the frame on a film, but required significant attention to produce quality reulity results.<ref name="Dungate" /> The Mechau film magazine only held enough for nine minutes so two recorders were needed to run in sequence in order to record anything longer.

=== Lenses ===

Lenses did not need a great depth of field but had to be capable both of producing a very sharp image with high resolution of a flat surface and of doing so at high speed. In order to minimize light fall-off on the perimeter of the lens, a coated lens was preferable. 40&nbsp;mm or 50&nbsp;mm lenses were usually used with 16&nbsp;mm in calibrated mounts. Focus was checked by examining a print under a microscope.

=== Sound recording ===

The camera could be equipped with sound recording to place the soundtrack and picture on the same film for single-system sound recording. More commonly, the alternative ''double system'', whereby the soundtrack was recorded on an optical recorder or magnetic dubber in sync with the camera, yielded a better quality soundtrack and facilitated editing.

=== Kinescope image ===

Kinescope CRTs intended for photographic use were coated with phosphors rich in blue and ultraviolet radiation. This permitted the use of [[Reversal film|positive type emulsions]] for photographing in spite of their slow film speeds. The brightness range of kinescope CRTs was about 1 to 30.{{Specify|reason=Units?|date=December 2023}}

Kinescope images were capable of great flexibility. The operator could make the CRT image brighter or darker, adjust contrast, width and height, rotate left, right or upside down, and positive or [[negative image]].

Since kinescope CRTs were able to produce a negative image, direct positive recordings could be made by simply photographing the negative image on the kinescope CRT. When making a negative film, in order for final prints to be in the correct emulsion position, the direction of the image was reversed on the television. This applied only when ''double system'' sound was used.

=== Film stock used ===

For kinescopes, 16&nbsp;mm film was the common choice by most studios because of the lower cost of stock and film processing, but in the larger network markets, it was not uncommon to see 35&nbsp;mm kinescopes, particularly for national rebroadcast. Fine grain positive stock was most commonly used because of its low cost and high resolution.

=== Common issues ===
Videotape engineer Frederick M. Remley<ref>{{Cite web|url=https://www.lib.umd.edu/special|title=Special Collections and University Archives &#124; UMD Libraries|website=Lib.umd.edu}}</ref> wrote of kinescope recordings:
{{blockquote|Because of the many variables in the combined electronic/photographic process, the quality of such recordings often leaves much to be desired. Defects often encountered in photographic recording include relatively poor image resolution; a compressed brightness range often limited by kinescope display technology to a brightness ratio of about 40:1; nonlinearity of recordings, as exemplified by lack of gradation in both the near-white and near-black portions of the reproduced pictures; and excessive image noise due to film grain and video processing artifacts. The final [[signal-to-noise ratio]] is often less than 40&nbsp;[[decibel|dB]], especially in the case of 16&nbsp;mm film.<ref>In ''Magnetic Recording: The First Hundred Years'', IEEE Press, 1998, p. 128. {{ISBN|978-0-7803-4709-0}}.</ref>}}

Because each field is sequential in time to the next, a kinescope film frame that captured two interlaced fields at once often showed a ghostly fringe around the edges of moving objects, an artifact not as visible when watching television directly at 50 or 60 fields per second.<ref>{{Cite web|url=https://www.howtowatch.online/video-codecs-software/|title=An Overview of Codecs and Video Processing Software|date=February 4, 2019|website=Howtowatch.online|access-date=4 August 2019}}</ref>

Some kinescopes filmed the television pictures at the television [[frame rate]] - 30 full frames per second for American [[System M]] broadcasts and 25 full frames per second for European [[System B]] broadcasts,<ref>{{Cite book|last=Morgan|first=Willard Detering|url=https://books.google.com/books?id=DvdGAAAAYAAJ|title=The Complete Photographer|date=1943|publisher=National Educational Alliance.|pages=3393|language=en}}</ref> resulting in more faithful picture quality than those that recorded at 24 frames per second. The standard was later changed to 59.94 fields/s or 29.97 frame/s for System M broadcasts, due to the technical requirements of color TV. Since these reasons did not affect System B, the color TV framerate in Europe remained at 25 frames/s.<ref>{{Cite book|last1=Pogue|first1=David|url=https://books.google.com/books?id=EvTWVImN-iQC&q=%2229.97+frame%22&pg=PA342|title=iMovie '11 & iDVD: The Missing Manual|last2=Miller|first2=Aaron|date=2011-03-16|publisher="O'Reilly Media, Inc."|isbn=978-1-4493-0651-9|pages=342|language=en}}</ref>{{efn|If electrical interference was present in the old 30 frame/s, 60 fields/s black-and-white System M format, a shutter bar would appear horizontally across the screen and not move due to U.S. electrical standards having the same frequency (60 [[Hertz]]) as the fields refresh rate in the picture. When color TV was standardized, the frame rate was shifted to 29.97 and the field rate shifted to 59.94 to allow a frequency shift not only to introduce the luminance/chrominance delay needed to share the information on the screen, but also to move the hum bar from a stationary position. As System B ran on 25 frame/s, 50 fields/s in black-and-white (to accommodate the 50 [[Hertz]] electrical frequency used in Europe), and had a wider bandwidth per channel, this issue was rendered moot.}}<ref>{{cite web | url=https://www.youtube.com/watch?v=3GJUM6pCpew | title=Why is TV 29.97 frames per second? | website=[[YouTube]] | date=3 October 2016 }}</ref>

In the era of early color TV, the [[chrominance|chroma]] information included in the video signal filmed could cause [[chroma dots|visible artifacts]]. It was possible to filter the chroma out, but this was not always done. Consequently, the color information was included (but not in color) in the black-and-white film image. Using modern computing techniques, the color may now be recovered, a process known as [[color recovery]].

Because [[videotape]] records at fifty [[interlaced]] fields per second and telerecordings at twenty-five progressive frames per second, videotaped programs that exist now only as telerecordings have lost their characteristic "live video" look and the motion now looks filmic.  One solution to this problem is [[VidFIRE]], an electronic process to restore video-type motion.