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-   -   Off topic / Extreme action/I love 50i (https://www.dvinfo.net/forum/canon-xl-h-series-hdv-camcorders/65171-off-topic-extreme-action-i-love-50i.html)

Jonas Nystrom April 15th, 2006 06:56 PM

Off topic / Extreme action/I love 50i
I think you get a little bit of topic in the thread "xtreme sport type shots with lots of motion". So here in this thread, a new question:

I tried out som action shots, and here is deal: I would like to shoot fast action @ 25f (living in the PAL world). My choice is a fast shutter, @ 2000 or something. In the picture, my daughter throw a stone, background is blue skies, and if I could freeze the whole sequense, the motion of the stone would end up in a dotted line!

And here comes the maybe stupid silly question: Is thera any work around? Could shout at fast shutter/25f without retain the "dotted stone line". Or is this a artifact created by the compression (HDV)? Or is it like my impression, fast action with high speed shutter is better in interlaced?

Bob Grant April 16th, 2006 05:50 AM

The answer is fairly simple. You're taking 25 frames per second but each frame only records 1/2000th of a second. So the first frame records 0.5mSecs of the stones motion, then nothing is recorded of its motion for 39.5mSecs and then another 0.5mSecs of its motion etc.
Result, a dotted line.
That's why ideally the shutter speed is as low as possible, around 1/40th at 25fps for video or 1/60th (I think, for film, the camera needs time to move the film).

Even at 50i you'll still get a dotted line, less so than at 25p though.

Of course at the lower shutter speeds you get motion blur, the object moves with the frame. That creates a problem for slo mo which is why sports stuff is shot with a faster shutter speeds but it makes the action look stroby. The ideal is to use a very fast frame rate but such cameras get expensive.

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