Iancraig10
lvl.4
United Kingdom
Offline
|
The judder that you see is a common artefact with 24 or 25 fps. To a lesser degree, 30fps. To some degree, you can get better detail in the video picture using slower shutter speeds, but less as far as movement goes.
Low shutter speeds = more resolution for a given bitrate. High shutter speeds = less resolution for each frame but much better motion tracking.
So for slow non-moving, or very slow camera motion shots, I use a slow shutter for more definition. For fast camera motion (like panning) I use a higher shutter speed for more fluid motion and sacrifice a little of the detail perhaps.
The speed of your pan makes the next frame appear too far away from the previous frame, so in effect, it is jumping across the screen. The frame rate is too slow for that speed of pan. It will show horribly on contrasty areas or vertical lines. The answer is to either not pan, or pan extremely slowly.
This effect can be seen in cinema footage very often, but they are better at disguising it, by having an out of focus background or twisting the camera as it pans so that the subject remains in the centre of the picture. (The background judders but you’re less aware of it because it’s out of focus!)
There are only three answers and one is to do with what happened with TV.
They used to show two fields (two pictures) every 1/25th of a second. This was to smooth motion. It was called ‘interlaced’ where half of the picture (every other line) was shown and then the other half shown 1/50th second later, so really, TV was two half pictures shown over a period of 1/25th second. In effect, they were showing video at 1/50th, although each frame was actually half a frame. We don't tend to use interlaced video any more and we are showing just ONE field every 1/25th second instead of two.
In USA, they showed two half frames every 1/30th second. (So 1/60th second frame rate using half frames)
So the answer is
A) Don’t pan.
B) Pan very slowly if you have to. Better to take two still shots of the scene.
C) Change frame rate to 50 or 60 fps and you will have way less of a problem.
In spite of all the gubbins spouted about 24 fps being cinematic, yes, it can be, but you have to be WAY more careful how you video it because of the problem that you are showing. Cinema professionals deal with the same issues, but they plan their shots very carefully to avoid it!!
Don't pan. Just let movement happen in front of a still camera and move (if you have to) DEAD slowly.
When you are panning, ask yourself, 'what are you trying to show'? With a pan, you are skirting over something so that nothing is really in focus properly. Your eyes try to find something to lock onto. A fast pan works better if you are following something so that it is still in the frame. Your eyes lock on to the subject and then see the background judder much less.
Video technique is quite different to stills and it also helps if you get the subject in focus and background blurred most of the time!
It's not the camera. It's just the way we see in comparison to a camera.
|
|