Bubbles in slow motion - The ins and outs of GH4 96fps and Twixtor tips

I havent posted to my Reflex Films log in for a while.


For those of you interested in 4k and 1k slow motion - and a little bit of twixtor (and shooting for twixtor optimisation) you might be interested in this short video i made.

Twixtor is a frame interpolation plug in that effectively builds extra frames to help create slow motion video - minus the super expensive phantom camera. I have been using Twixtor for 6 years now.

vimeo.com/115970980

I have been using the panasonic gh series of cameras and the Gh4 has especially been an awesome camera. With Image stabilised fast zooms like the 12-35 f2.8 you can get rock solid reliable results hand held if need be. Most other lenses will micro jitter once you get them off the tripod or monopod.

1080p at 96 fps is very handy - and while the pixel peepers might say the video can be a tad soft - i find it far more flattering to skin tones than super sharp 4k. So sometimes a slight shortfall in specs can work for you...

I was slowing down as much as 30% - so effectively delivering nearly 300fps results.

You need to know when to go slow - fast motion and blur in frame is not your friend - steady action or slower bubble movement is the time to really slow down the video.

On this particular video i shot with the Panasonic 25mm f 1.4 wide open (unlike many other lenses it maintains its performance wide open) in maxing daylight - and into the sun - i figured i could control my light with super fast shutter speeds - which also help Twixtor to deliver its best results (by removing motion blur)

Paradoxically you would normally shoot deep depth of field for Twixtor as twixtor hates blur - but i had to live with the shallow depth of field that fast apertures bring to be able to get my shutter speeds this fast(1/800 - 1/2000th were used)

So there it is - i hope other film production nerds out there find this helpful - i'm pretty happy with the results!

I once had the opportunity to test Twixtor (pity, they don't offer a trial, don't they?) on a friends machine; I noticed, just 'drag'n top' the effect onto a clip doesn't work - at last with my material ... but, had just ~30min for testing, had no idea how to use it)

Created the same 'wobble' as in this test of mine with FCPX' built-in Optical flow:

(at the end of the test, "10% speed" - watch the ball: 'rotation' kills OF :lol: )

So, would you like to share your 'settings' within Twixtor?
e.g. did you work with background/foreground mask and-what-not? :huh:

Hi Karsten,

Twixtor do a watermarked demo so you can try before you buy.

It does take a little bit of learning to use - and especially proactively shooting for twixtor will help a lot.

You can see from your 10% test that the ball breaks the limits of what the optical flow can track and interpolate.

Optical flow isnt bad - but twixtor just seems to use better algorithms / tracking. As you approach limits with FCPX optical flow Twixtor will continue to perform - but eventually you will hit limits with Twixtor too. to put it another way - all things being equal -optical flow may get you to 50% slow motion - but Twixtor will take you to 25% for the same shot before you get a breakdown.


When i shoot for slow motion i allow for the fact that twixtor needs a long base clip to fit its slow motion into (this avoids the nesting or compound clip workflow- which is easy enough but takes up a little more time) - so i tend to shoot with large "handles on my media if i think i am going to be slowing a shot down.

In this mode the software is pretty much drag and drop - and then set your speed - this should do the trick for 80% of your work.

Once you get more skills twixtor does beautiful speed ramping with the use of key framing speed changes - something that FCPX doesnt do particularly well.

You can pprep the image with edge enhance and motion blu compensation (which adds some post digital sharpening to offset any smoothing of the video) - but these are mostly subtle tweaks.

(As i dont use twixtor pro there is no manipulation of mattes or masks)

Reflex Films wrote: … Twixtor do a watermarked demo so you can try before you buy.…

oops, wrong/old info on my side, missed that, thanks!

Thanks for you detailed advice!
Read somewhere advice about some sort of 'voodoo', to arrange the clip inside a 3x3 matrix of the same clip, to give the algorithms 'beef' to calculate. :S
And, general advice: avoid any 'complicated' background, most demoes show a blue sky or similar ...

I should give Twixtor a 2nd try soon (Santa will deliver a belated gift ... new camera, yippieh)
But my households Secretary of Finance told me, 'we' don't need Twixtor. .... hmmmmmm