[old_tv_nut]

Answers in bold [EDIT - AK changes all-bold to lower case]

Originally Posted by dvtyro

@old_tv_nut, frankly, my math is too rusty get into it again. I do not strive for understanding these graphs on a level of a video engineer, but i would like to be able to compare two machines looking at the graphs. After all, these graphs were published in all pop-sci magazines, and a regular reader was supposed to understand them. All i want is conceptual understanding.

Please, see the attached picture.

• deviation from sync tip to peak white is used for brightness - yes/no ?
  Yes
• deviation has no relation to resolution - yes/no?
  Yes
• wider deviation means more contrast, means more s/n - yes/no?
  Yes, means larger signal from the fm detector
• moving the sync tip to higher frequencies, even if deviation is not changed, extends luma bandwidth, which increases luma resolution - yes/no?yes
• luminance sideband to the left of sync tip describes the level of detail?
  Yes level of the sideband is determined by the level of detail
  
  or the whole luminance band including the deviation describes the level of detail? Higher frequency means more detail?
  Frequencies further to the left represent finer detail. Note that fm normally produces symmetrical sidebands above and below the range of deviation. In video recorders, the upper sidebands are suppressed due to frequency limitations of the recording process (head gap, etc.) this assymetrical sideband result is not ideal but the distortions can be small enough to not be of concern.
  
• is the detail described by the luminance band for a "pixel", for a line, for a whole screen? The graphs i posted show a wiggly line between sync tip and peak white, i presume this is the third dimension, time. Sync tip is a pulse for the start of each line, right? So i can draw this graph in three dimensions: (f, u, t). The simplified 2d graph that i posted before in (f, u) coordinates is a snapshot of one "pixel", how much detail it has, how much frequency information. The higher the luminance frequency, the more high-frequency detail, that is, more alternating white and black pixels? Um, so i guess i cannot get it for one pixel, maybe for like two adjacent pixels? Not sure...
  Here you have run into mathematical fourier analysis theory. A single frequency in the frequency domain represents a sine wave that is continuous for all time past and future. So the spectrum conceptually is the result of measuring the electrical signal over infinite time, and therefore includes all frames, lines, and pixels. Practically speaking, of course we measure over shorter convenient time periods. A typical use of a spectrum analyzer might do the measurement over a few lines or a frame. This means that we can have the short term spectrum update every few lines or every frame. The mathematical result is that the spectrum resolution gets a bit blurred, in inverse proportion to the measurement time.
  
• were beta vcrs more compatible from the start compared to vhs, or moving deviation to higher frequencies without widening the deviation is inherently more compatible? If jvc did the same, would regular vhs machines be able to play such an improved format? Because from what i've read, old beta machines could play superbeta recordings.
  I don't know. You will have to search further, maybe in ieee literature.
  
• umatic, including umatic sp, uses the same "color under" technique, and looking at the graphs, it is no better than svhs and hi8. I suppose, the only reason umatic was preferred by pros was because they had all the needed interconnects, could connect to tbc, had timecode, etc. But the sheer image quality of an original recording was no better than on svhs and hi8, yes/no?
  I don't know. Depends on the details of the comparison. If u-matic had a higher tape speed and/or wider tracks, the signal to noise ratio would be better.
  
• i suppose, regular vhs has never been used by pros. Well, maybe by some, on some small regional stations, but never at a large scale, and there were no standard vhs machines that had all the needed pro features to interconnect with other pro equipment?
  I don't know, but i suspect even small cable head end public video facilities mostly used u-matic. There can be other considerations besides video bandwidth, such as time-base correction to meet fcc broadcast standards.