FORUMS: list search recent posts

C300 : Converting in-camera overcranked footage back to real time.

COW Forums : Canon Cameras

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Dejha Ti
C300 : Converting in-camera overcranked footage back to real time.
on Sep 14, 2016 at 3:43:27 am

I'm editing a project where we wanted the ability to have slow mo for some shots and realtime for other shots. The DP used the C300's slow mo function where it it converts 60fps into 24fps making the footage slow motion in-camera. I've learned after the fact, that this was not the way to approach this however we are now stuck with ALL slow motion footage. I haven't found a reliable way to get the footage to play back at normal speed with out any artifacting. The two directions i've found are 1) Low quality results: Speed up the footage by 250% which makes the video look sped up 2) Cut out frames, add new frames and then utilize frame blending to improve the motion quality. For the latter, I'm still unsure of the best tactic (mathematics) and optical flow program/plugin to use (i.e., twixtor, etc).


Return to posts index

Todd Terry
Re: C300 : Converting in-camera overcranked footage back to real time.
on Sep 14, 2016 at 4:35:24 am

Firstly.... welcome.

Secondly... ouch. I don't want to be blunt and say your DP made a boneheaded move.... but....

Actually what you DP did is sometimes the only option. If you are doing a shot where you must have a slow-mo version of the shot, and it must be "smooth" slow motion, and it's an absolute one-time or one-shot deal where you can only photograph the action once... then yes, you should overcrank. But in virtually all other instances, you should overcrank only the shots you intend to slow-mo, and overcrank the exact amount that you want. You are not alone, I've frequently heard people say they are going to overcrank everything because they might want to slow-mo some of the shots later... maybe. This is a huge mistake... but I think you've learned that already so I won't lecture about it.

In theory... playing back the 60fps shots at 250% on a 24p timeline should give you the correct speed motion. There is nothing wrong with your math... you got the math exactly right.

You say it looks "sped up." I'm betting that it isn't actually sped up, but is normal speed... but just looks sped up to you. Here's why... what you are seeing there is footage that is similar to footage shot at normal speed but with the "narrow shutter" look that comes from a higher-than-normal shutter speed. When shooting 24fps, a "normal" shutter speed would be 1/48th of a second. You were shooting at 60fps, so I'm guessing that your shutter speed was at least 1/120th of a second (or maybe even higher, depending on what your DP did). So when you speed it up, you get footage that has the speed appearance of 24fps, but the shutter appearance of 1/120. When shot with a normal shutter (1/48th) each frame will have a fair bit of motion blur in it, which your brain needs to interpret motion as smooth. But when you're viewing 24fps footage with a 1/120th of a second shutter, because of the fast shutter speed there will be very very little motion blur in each frame... each frame will be pretty darn sharp. The result is that jittery staccato "narrow shutter" look that action movies use to look more "actiony"... and I'm betting that's what you are seeing... and it's making you think they footage looks too-sped-up when in reality the actual speed is correct.

Unfortunately of all the things we can change in post production (which these days is darn near everything), you are fairly stuck with the shutter speed you've shot at... that is one of the very difficult things to manipulate in post. Well, in reality, you actually can't manipulate it at all... but you can simulate it's manipulation a little bit in some instances.

If you have, for example, a very fast pan that looks stuttery, you can add a little bit of a horizontal directional motion blur filter just while the shot is panning. Or a vertical filter if you are fast panning. Isolating moving objects within a non-moving scene and adding motion blur to them is much much more complicated. Depending on the shot it can require a lot of layers and masks and some painstaking frame-by-frame rotoscopting to add just the motion blur needed just where you need it in the right areas, amounts, and directions. For an extremely short shot (a second or two), it might not be too big of a deal. For longer shots it gets a lot more complex... and at the very minimum I'd suggest a compositor who is an After Effects wiz, or ideally some much more advanced compositing than that, such as the voodoo that Autodesk can do (Flame, Smoke, Flint, or Inferno compositing).

Good luck.... and I'd tell you to remind your DP to shoot at the desired frame rate next time.... but I bet you've already whacked them over the head by now.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



Return to posts index

Blaise Douros
Re: C300 : Converting in-camera overcranked footage back to real time.
on Sep 14, 2016 at 6:49:21 pm

Furthering what Todd said; I've had decent luck with speeding up the footage to 250% and enabling Frame Blending (rather than Frame Sampling or Optical Flow) as the setting for the clips and timeline. You get a modicum of motion blur from the combining of frames, so the motion looks a hair more natural. Give that a try before you do anything else, and see if the results are good enough. You may need to do more in-depth processes on certain shots, but this might be a good-enough solution that gets you most of the way there.


Return to posts index


Chris Wright
Re: C300 : Converting in-camera overcranked footage back to real time.
on Sep 14, 2016 at 4:37:52 am

best honest advice, buy a Snell Alchemist OD. or find someone who owns a alchemist or teranex converter. anything else will have artifacts.


Return to posts index

Aaron DeWitt
Re: C300 : Converting in-camera overcranked footage back to real time.
on Sep 22, 2016 at 5:37:50 pm

Another option for adding blur is to use "Pixel Motion Blur" (built-in) or Reel Smart Motion Blur (Re:Vision FX plug-in) in After Effects. If you crank the samples up, you can usually avoid nasty artifacting, depending on how complex the scene is.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]