shutter speed setting for ramping S&Q motion in post

[Paul King]

Hi Guys,
I'm shooting a promo over the weekend and one of the takes requires the ability to ramp the shot in post as I know this is not possible in camera.
What we intend to do is shoot at 720p 25p/50fps while our artist is lip syncing to his track played at double speed. The idea is then to play the timeline out at 25fps, which will be normal speed and then ramp to slow motion at certain points whist retaining lip sync.

My question is regarding shutter speed settings, I did some tests at 25p/50fps with shutter speeds of 100th and a 50th and when played back at 25fps the 100th was quite choppy and the 50th slightly better. Coming from a film background I am used to shooting slow motion with a 180 degree shutter angle (unless a tighter or looser angle is specifically needed) and ramping in camera. Would i be right in thinking that the 100th was choppy because when played back at 25fps all that final cut did was lose half the frames whist retaining a 100th shutter speed, also will shooting in progressive rather than interlaced have an effect on the shutter I should be using?
Will shutter angle set at 180 degrees just have the same issues?

My thinking now is that because 80% of this particular take will be played back at 25fps, maybe I should shoot at 25p/50fps with a 50th shutter to allow for smoother playback at the 25fps playback and allow the speed ramped sections to suffer from a small amount of blur that this will have.

We are also shooting takes at 30fps and 25fps so we are safe as far as coverage is concerned but it would be nice to have the option of ramping.

Any help is really appreciated.

[David Knaggs]

Originally Posted by Paul King

Would i be right in thinking that the 100th was choppy because when played back at 25fps all that final cut did was lose half the frames whist retaining a 100th shutter speed ...

Hi Paul.

This might not be any help but, if you changed the speed of your clip (in the Final Cut Pro sequence) to 50%, then I wouldn't expect it to throw out any frames. (I would only expect it to throw out frames if you put a 50 fps clip into a 25 fps sequence and left the clip speed at 100%.)

[Paul King]

Hi David,

I think the clip was just played out at 50% so you would be right, I try to keep out of the editing process and get involved at the grading stage. What I think happened was that the clip was played out at 50% but retained the 100th shutter whereas I made the assumption that like film the shutter is linked to the frame rate and will therefore stay at the same angle throughout the speed ramp (I know this can be altered to retain t-stop if needed).

From a post point of view do you think footage shot at 25p/50fps with a shutter at 1/50th will look overly 'smeared' when we play it at 25fps then ramp up to 50fps?

Thanks
Paul

[David Knaggs]

I guess this brings up the delicate subject of "acceptable motion blur". I once edited a project shot at 24 fps with a "1/24th shutter". Obviously the scenes with extreme, fast motion had the most noticeable motion blur. Is the artist going to be wildly gyrating or shaking his head around while he sings? Or is he going to be fairly sedate in terms of his head or body movements?

Maybe it would be best just to grab the camera and someone nearby and get that person to pretend to sing. Then do one shot of "wildly gyrating" and another of "steady and soulful". Then get your post guy to try the ramping with these two pieces of test footage.

But only if you have the time and resources. Just an idea.

P.S. By the way, welcome to DV Info!

[Paul King]

Thanks David, very nice to be here.

Our artist will be quite sedate, we aim to shoot most of this at 30fps to give that ethereal flowing look. The set-up is the EX3 with the letus ultimate and Nikon zf lenses, this will all be mounted on the steadycam flyer and I don't plan on any fast pans. The ramping will take place at points where there is no sync and when the artist turns to see someone in the club or does certain gestures.
As I said, I'm used to being able to control the shutter angle but due to budget constraints this seems to be the only option to attain these ramps without going into after effects or motion.

Thanks again

Paul