March 15, 2015 at 1:14PM

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Working SlowMo into a Doc - Production and Post

I'm gonna be shooting a doc quite soon and I wanted to have the flexibility in post to change speed and not have to make the decision the split second before I hit record. It's gonna be very run and gun, one shot, one chance kinda stuff.

My first question is if I shoot the whole thing at 100fps to finish as 25, to what degree will the shutter angle show?
That it so say to avoid loosing the look of natural 180deg motion blur.

When I shoot 60i (the post cheat) slow mo on my C100 it looks horrible unless its speed is set to the intended 40%. But I've been working some grades on 180fps Dragon footage and when I speed that up to give me normal motion it looks totally fine, none of that strange "The Hobbit 48fps, looking at the screen for more than 30 seconds makes me hallucinate" nonsense.
I'm gonna shoot it on an Amira, so switching frame rates is very easy, I just wanted to see if I could make the shoot even easier!
Thanks in advance
J

6 Comments

Is because is not progressive. You must shoot 60p not 60i.

March 16, 2015 at 1:16AM, Edited March 16, 1:16AM

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Rag├╝el Cremades
Film producer and director
8131

I thought someone would say that! It was a silly example, but I have seen a lot of other stuff that's shot at high progressive rates that's disturbingly sharp to the eye.
Are you saying I shouldn't worry and go ahead and shoot at whatever speed I want?
Thanks!

March 16, 2015 at 12:35PM

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James Coote
Director of Photography
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An option for your shutter speed problem is to shoot everything at your desired 100fps with the correct shutter speed (1/200 would give you a 180degree shutter) and then in post add motion blur. After effects has its pixel motion blur effect which allows you to adjust shutter angle, samples, and detail and in my experience it does work quite well. Another option would be to go with the 3rd party plugin Real Smart Motion Blur which apparently is much faster with around the same results as pixel motion blur. Obviously this can be time consuming depending on how long your final project is and how much of it you need at normal speed vs slow motion. One thing to take into consideration is you can always add motion blur but you cant take it out.

March 16, 2015 at 5:50PM

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Thanks Jamie, that is extremely helpful... I was wondering if there was something more efficient then pixel blur for AE!
I've read and seen that 48fps with a shutter angle of 140degrees is used a lot, do you have any idea what there is to gain in adding that extra blur? As I agree with you, rather have too sharp then too blurry any day!
Would also love a few 2/4k 200fps Amira files to play with if anyone has one!

March 17, 2015 at 4:34PM, Edited March 17, 4:34PM

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James Coote
Director of Photography
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My solution would be for the more extreme situations (shooting everything at 100fps as you had mentioned) where you are going to have a much bigger difference in shutter speed between 180degrees at 24fps and 180degrees at 100fps (1/48th vs 1/200th). The extra motion blur added in post is going to negate that strobing effect that you get shooting at higher shutter speeds/lower shutter angels. If you are just thinking of shooting everything at 48fps then you are going to run into a lot less of a headache and shooting at a 140degree shutter would probably work nicely. Obviously you wont be getting as slow of motion as your previously mentioned 100fps which could be a drawback. You can also look into frame interpolation to slow down your 48fps footage but depending on the amount you are slowing it down it can have mixed results.

March 17, 2015 at 4:58PM

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I think that sounds good! I'm slightly worries as I've never added blur in AE, let alone shoot a doc at 100fps!
I'm starting to worry about media! 100fps in 4k ProRes 4444 is 22gb/min.
I've never slowed video with interpolation... What rate would you feel ok to push 48fps footage to? 50% at 96fps or is that already too far?

March 20, 2015 at 5:20AM, Edited March 20, 5:20AM

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You voted '-1'.
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James Coote
Director of Photography
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