FORUMS: list search recent posts

Slow motion question

COW Forums : DSLR Video

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Scott Gaskin
Slow motion question
on Jan 18, 2015 at 11:06:56 pm

Hi there,

I am going to be shooting a music video soon and want to include some slow motion footage.
I am shooting on a Canon 7D and will be using 24fps for most of the shoot.

I'm just wondering whether to shoot the slow mo stuff at 50fps or 60fps. I understand that the general rule of thumb is that the shutter speed should be double the frame rate. My camera gives me the option to set the shutter at 1/100th (if shooting at 50fps) but if I shoot at 60fps I only get option to set shutter to 1/125th and not 1/120th. Will this be a problem?

Also is there much difference shooting at 50fps compared to 60fps? I want the best quality slow mo possible so just wanting some advice on which to go with?

Thanks in advance

Scott


Return to posts index

Steve Crow
Re: Slow motion question
on Jan 19, 2015 at 4:01:42 pm

60fps 1/125th

Steve Crow


Return to posts index

Marta Breijo
Re: Slow motion question
on Feb 4, 2015 at 5:26:04 pm

Hi Scott,

I was wondering right now about the combinations of shutter-fps-movement speed I can record without getting a horrible judder effect (and any other shutter problems). I'll look for a combination table, or make one some day. To be honest, I'm not sure how much of that would affect a slowed footage. I'd go for a trial-and-error method before the day you shoot... even if it's only to make sure the camera and movements you will use have an opportunity to work fine in the end.

That being said, I do have an answer for your question about 60fps at 1/125 shutter. There are mechanical limitations for 60fps being shuttered under 1/125th. So I think 1/125 should be fine for 60fps... at least that's the combination usually chosen for 60fps.

My advice in any case is... avoid moving too fast with your camera (probably the "7 second rule" will help), record at the highest fps you can, and use a tripod or some support to make your picture the stablest you can. Those will avoid post-production nasty fixes.

As to the difference between 50 and 60 fps... well, 60fps rendered into 24fps will do as slow mo, but 50... it's basically just double the real speed. I'd go for 60, not only for more slow mo effect, but also because the more "picture info" you get, the better. You can get rid of anything you don't want later... but to make sure you get all you need, just in case I'd go for 60.

There is a good article I read some time ago about shutter speeds you might find useful, even if it's only to understand the reasons behind the shutter speed choices: http://www.mikemccormac.com/news/tips-and-advice/item/619-whats-the-right-s...

Cheers,

Marta


Return to posts index


Scott Gaskin
Re: Slow motion question
on Feb 4, 2015 at 7:28:31 pm

Thanks for the reply Marta.

Are there issues when slowing down your footage in post if you are not using a tripod then? I plan to shoot some shots on a tripod and some using a hand held rig for the slow motion footage.

I also plan to shoot a scene where the camera is moving away (backwards on a makeshift dolly with camera operator hand held) from a group of people as they are walking toward the camera and to slow down in post. Will this cause me problems do you think?

Many thanks

Scott


Return to posts index

Marta Breijo
Re: Slow motion question
on Feb 5, 2015 at 1:17:35 am

Well, any kind of movement with a CMOS sensor camera may cause problems, but most things you can fix with some post-prod tweaking. I use AE, which is got some very good tools; and there are also some amazing plug-ins out there that will do almost anything.

But there is one thing I'm always concerned about, and it's the judder/stutter/jitter problem (it's got many names haha). It's easier to show it than to explain it: That choppiness is something many of us struggle with when using DSRL for video, even when respecting the "xFPS + 2xShutter" (what's the name?) rule. I do not know in depth the reason why it happens, but it happens a lot. And the worst is... there is still no plug-in and no tool to fix it. You can smooth it a little with motion blur, and try different fps redering but no real fix for digital video (it appears that it gets fixed with interlaced rendering, but ofc, interlaced will only have a nice look for TV, but not PC monitors and such :S).

And so that would be the only problem I would be concerned about. Mainly because you are going to record a music video, and that sounds like a lot of movement. Be careful with fast pans, and give special love to hand held camera shots. For me, this article shed some good light on the problem: http://kb2.adobe.com/community/publishing/908/cpsid_90843.html It has some really good advice on how to avoid that horrible effect.

In general, you can use tripods, dollys, and any support method you feel that will give your project the best look, none of that should cause problems. Also, you can add extra slow motion with a plug-in called Twixtor. Sometimes I shot at 30 or 25 fps, and after the post production my boss came in and asked to heavily slow down something... that plug in saved my life haha It does an amazing job. However if you plan to slow down even more (more than the final 24 fps), you will see you start getting that judder effect. That is essentially because your editing software will start "making up" the frames it doesn't have to fill the gaps, and that means duplicating the ones it does have, which ends up in... judder! (ugghh). That's why I said before it's better to shoot at the maximum fps you can, so you get the fastest fps, and then if you need to get rid of some frames it's always easier than "making them up" (gee, I hope I'm not getting you confused!).

Oh and.. you probably already know this but just in case, if you happen to need stabilizing and/or removing rolling shutter problems, all in post-production, AE (from 5.5 on) has the Warp Stabilizer tool. Since you are going to use a 7D (I have the same camera btw) you might encounter some rolling shutter at some point.

I hope this helps, cheers!

Marta


Return to posts index

Scott Gaskin
Re: Slow motion question
on Feb 6, 2015 at 6:35:26 pm

Thanks so much for your time to send me all this info Marta. Very good of you. Seems I have a lot to get my head around!

Much appreciated

Scott


Return to posts index

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