Shooting 1080/50p and editing in a 25p FCP X project is the same as shooting 25p? Not quite . . .

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Level 7

24,133 points

Shooting 1080/50p and editing in a 25p FCP X project is the same as shooting 25p? Not quite . . .

For the last year I have been shooting 1080/50p assuming that if I edit it as 25p it will be exactly the same as shooting 25p originally.

However, there is one thing I probably overlooked . . . shutter speed.

Presumably 1080/50p is shot with a shutter speed of 1/100 second whereas 25p would be shot at 1/50 second.

Using a shutter speed twice as fast will result in a slightly more staccato or jerky motion when played back at 25fps.

DRAT !

Wasn't life simpler when you could only shoot 25fps or 30fps interlaced footage!

OS X Yosemite (10.10.1), Mac mini i5 2.5GHz & iMac FCP X

Posted on Mar 10, 2015 9:35 AM

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Answer 1

Ian R. Brown Author

Level 7

24,133 points

Mar 11, 2015 1:06 AM in response to thesurreyfriends

I didn't say they were.

For normal motion shot at 50fps to look reasonably smooth, a shutter speed of 1/100 second is required . . . the 180 degree rule which basically means that you double the fps to give the shutter speed fraction which is sufficient to provide the necessary amount of motion blur.

Similarly 1/50 second is needed for video shot at 25fps etc.

Faster shutter speeds will increase the jerkiness progressively . . . which can be used to artistic effect such as in the staccato, violent action scenes at the start of "Saving Private Ryan".

However, for film requiring a smooth and natural depiction of motion, high shutter speeds are anathema and to be avoided like the plague.

On a similar note, progressive video tends to appear less smooth than interlaced shot at the same fps because the interlacing increases the apparent amount of blur.

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Answer 2

Mar 23, 2017 1:23 AM in response to Ian R. Brown

May i ask a simple question. All experts seem to have taken extreme settings.

What if i shoot at 50fps at 1/50 SS ( and NOT following 180 degree rule purposely) and then drop frame after editing to 25fps. It will still have 1/50 SS. Question is, Will this setting offer me SAME affect as that of shooting at 25fps at 1/50 SS native ( and folowing 180 degree rule )?

It will give me flexibility that i need to retain my work in either 50fps or 25fps.

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Answer 3

Mar 10, 2015 3:03 PM in response to Ian R. Brown

Presumably 1080/50p is shot with a shutter speed of 1/100 second whereas 25p would be shot at 1/50 second.

Shutter speed and frames per second are not the same thing and are basically unrelated.

http://www.mediacollege.com/video/camera/shutter/shutter-vs-fps.html

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Answer 4

Mar 10, 2015 3:47 PM in response to thesurreyfriends

thesurreyfriends wrote:

Presumably 1080/50p is shot with a shutter speed of 1/100 second whereas 25p would be shot at 1/50 second.

Shutter speed and frames per second are not the same thing and are basically unrelated.

http://www.mediacollege.com/video/camera/shutter/shutter-vs-fps.html

Erm, shutter speed and frame rate are often misunderstood but they are totally related and bound by physics. Shooting at 25fps, one can set a shutter speed of 1/50 second and achieve images that have little or no motion blur. Shooting at 50fps, one cannot select a shutter speed of 1/25 second without deliberately choosing to do so by overriding the camera's defaults. Shooting at 50fps using a shutter speed that is twice as long as the frame rate results in 25 frames per second of smeared video. I've done similar with my olde DV camera, shooting at 1/4sec onto 60 fields interlaced. Interesting but silly effect.

The OP is correct in his assumption about the results he realized.

There are software filters that will blend 50fps and turn it into a weird form of 25fps. The visual effect is highly stylized and not at all like shooting 25. It can be done by hacking the 50fps into 25 fields of interlaced video, which runs at twice normal speed, and then speed adjusting back out to 25fps. Umm, I may have left a step or two out of that recipe. Used to do it in After Effects with video from a super slow motion system that shot 90fps which ran at 3 times normal. To run that at normal speed, without throwing away the extra frames, we used frame blending, echo, CC Time FX and speed conversion to create these weirdly silky scenes. That was a long time ago.

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Answer 5

Ian R. Brown Author

Level 7

24,133 points

Mar 11, 2015 1:37 AM in response to Karsten Schlüter

Thanks for your input David and Karsten.

I saw Karsten's link a year or so ago.

Unfortunately there appears to be no solution to my dilemma David, as your "workarounds" sound worse than the "disease".

For anyone not familiar with my technique, I like to shoot 1080/50p as it gives the highest possible quality in both image sharpness and smooth motion and for the occasions when it is required, I can effortlessly edit the resulting video as 25fps.

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