Slow Motion

[David Ethridge]

I have filmed a clip in 1080i 24P on a CF card of my subjects and when I do half speed I dont get a smooth slow motion of the couple. It looks like vibrating edges. Is this the nature of progressive shots in my weddings or is there a trick to smooth slow motion?

[Steve Phillipps]

The most basic post production half speed is just doubling up the frame (ie repeating exactly the same frame twice) which is inevitably going to be very jumpy. There are various programs and plug-ins that "interpolate" the frames, sort of looking at 2 frames next to each other and trying to make one that would be half-way between the two. Some of these are better than others, but even the best are never going to look anything like as good as real slomo.
Another option is to shoot 60i and de-interlace, with programs separating the 2 fields into 60 frames and filling in the missing lines. Again not as good as true slomo though.
Steve

[Matt Stewart]

Forgive the "noobie" question, but when you say "true slo mo" are you referring to cameras specifically designed for slow motion? and is this the only way to truly achieve the look we see so often in action films or nature documentaries.

[Zach Love]

Matt, if you want really smooth slow motion you NEED a camera that can shoot a high number of FPS (frames per second).

These people now make cameras that can record up to 1.4 million fps!
High Speed Cameras: Digital High Speed Video Camera Systems and Accessories.

I think there are only a few dozen Phantom HD (slow-mo cam made for TV / film) cameras out there, and they cost a few grand a day to rent, but they can produce amazing images.

The Z7 can shoot in bursts of 120fps, which you lose some quality in resolution, but gain in smoothness. (This is something that a few on Sony's cameras can do & no Panasonic, JVC or Canon camera can.)

If you don't want to use the slow-motion function of the Z7, you should always shoot in interlaced. You NLE (non-linear editing software) will have an easier time taking the 60-fields per second & making a cleaner slow-motion image, than taking 24 frames & making the video smooth.

Just think that 24p at 50% is only 12fps, well into the range of the human eye being able to see individual frames.

Now if your problem is really weird sharpness when you slow down the image, it could be the NLE you're using. Most likely it doesn't do slow-mo well, or it needs to render the image.