I finally got an answer to the juddering issue I have been seeing a lot in my footage.
Juddering looks like a little lag that shows when panning.
I was not sure what caused it, but the net coughed up some common problems, mostly subscribing to the “panning too fast” school of thought. Apparently, the rule of thumb goes something like “it should take seven seconds to go from frame edge to opposite edge in a pan”. This is dependent on a lot of other factors like lens coverage etc, but the rule is “slower is smoother”.
Problem is, it still happened. A subtle but un-ignorable series of little jumps. That gorgeous smoothness of film in cinema just seemed beyond me.
The variances of cameras, lenses, sensor speed, shutter to frame rate combinations, panning speed, resolutions all seemed to come up at one point or another, but what is the culprit, why is digital panning such a mine field?
I see it in professional productions, old and new, film or digital, then see examples of perfection in the art from just phone footage.
Turns out it is down to frame rate shot at compared to the playback devices hertz rate, which with most devices is 60 or 120 hz. Recording at “cinematic” 24fps for smoothness actually makes this worse. By not matching the frame rate to the playback hertz rating and using a slower frame rate which exaggerates judder (smooths other movement), there is more than a mild chance of a frame or more being “dragged” to fill the time line (24 into 30/60/120 does not fit evenly). I have been using 25fps as a compromise between 24 cinematic and to match our PAL region. I though it a better fit than 30 fps. Turns out most devices need 30fps.
Does this mean shooting at 25 to avoid recording flicker and editing at 30 to avoid playback judder or the other way around? Not sure, still researching. Sure enough today I got some flicker at 30p so it may be a case of shooting one, then up-rating in processing.
It looks like a high frame rate (with 180 shutter rule applied), to match the NTSC rates for playback, will help, but may not be the perfect answer.