Slowmotion in broadcasting (sports, etc.)
Something I'm wondering:
When slow motion is needed in film or fictional video productions, the cameras are overcranked. But how is this done in broadcasting? E.g. I would expect sports (soccer, etc.) to be shot at 50i/25fps (PAL) or 60i/29.97fs (NTSC), yet I come across great-looking slowmotion of goals, etc. How is this achieved? |
Altering the playback rate of the clip to usually 70%ish of the normal fps. It really all depends how slow they want it. When the playback rate is slowed down for something shot at 29.97fps, you can get a pretty smooth looking slow motion. I mean of coarse it's not as great as higher frame rate, but it is good enough for what it needs to do with sports replays and whatnot.
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So are frames just repeated then in a certain pattern?
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I believe Sony has a super slow-mo camera that can do 500+ FPS that was used at the Olympics.
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I was curious as to costs of used broadcast systems and checked out ebay a while back.
They had a broadcast vtr that featured super slo-mo. I believe it was a Sony brand. I don't think they would have a camera set up for slo-mo on the cameras while recording... Maybe high speed recording? Anyone? |
In typical sports shows it doesn't appear that they use higher frame rates for slow motion. I am actually often surprised by that. Particularly in baseball - they always show slomo of a pitch coming in and it isn't very good. I think if that had one single 120 fps camera behind the mound it would help the coverage a lot. Baseball is an oddball there, though, because it is pretty much the only sport where you want the shot from the exact same angle every time.
The exception here is tennis. The close-up line cameras that show the ball compressing as it hits the ground are obviously higher-rate (but lower quality) cameras. |
Ok, so the only way to make slowmo from regular 25fps/29.97fps shoots would be repeating frames, right?
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I always thought...
I was told that the frames are just repeated, and slowly progressed... but there are specific cameras that capture above standard FPS, available from Ikegami and fomerly Sony. With analog, it was better to run a specific cam for slow-mo. And then digital, you can edit it down and all, most of time less than 3 minutes.
edit;; Thompson/Grass Valley also manufactures a high FPS camera. |
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The lower end editors do this. It really becomes apparent when you slow it WAY down. Then it's really jerky as the frames tick by like the second hand on a clock. But better slow mo interpolates between frames and figures out the inbetweens. Similar to keyframing, it determines where the pixels would shift when moving from one 'true' frame through the 'tweens' to the next 'true' frame. Sometimes thought this can be easily recognized in the video and doesn't always work either. Best bet I've heard is to film at 60i, so if you double the length, you can actually get 30p, but at half vertical resolution. |
I've got a buddy who does lots of freelance for fox sports and they love his varicam, can overcrank to 60fps in HD.
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You guys should check out the cricket coverage in the UK. They have all sorts of fancy kit.
Hawk eye, to track the exact path of the ball and predict it's path after a defect. Super slow-mo cameras (around 300 fps I think) ... and of course, the "Snick-o-meter" |
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