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1080p and 720p in the same sequence/video

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Fernando Bobadilla
1080p and 720p in the same sequence/video
on Mar 10, 2012 at 6:53:49 pm

I'm using a DSLR to capture 720p/60fps to create a smooth slow motion effect for my music videos.

I'm also using 1080p to capture real time footage of the musician singing.

I noticed when I bring the 720p footage into FCP it looks smaller, and I'm assuming those are the numbers left of the forward slash of 720p (xxxx/720; sorry, i dont know them off the top of my head).

What can I do to conform the 720p footage to make it the size of the 1080p footage?

Also, is there any tips of how to help me make 720p footage look more like 1080p footage? I'm asking this because i noticed that there are changes in color temperature when I switch from both settings.

I'm guessing that I might either have to capture everything in 1080p, and sacrifice the slow motion that i desire for the sake of the story of the music video, or, shoot everything in 720p and sacrifice some of the clarity for it is not 1080p...

Any help will help; thank you for your time.

Fernando Bobadilla


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Jeff Meyer
Re: 1080p and 720p in the same sequence/video
on Mar 10, 2012 at 10:28:34 pm

By "Conform" I assume you mean you're opening the 720 footage in Cinema Tools and using that to conform the footage to 23.98? If you aren't that's the proper way to handle the footage for slow-mo. Be aware that this process isn't reversible, so if you want to use the footage in real time at some point be sure you make a second copy of the file in Finder before conforming.

With regard to the footage looking smaller, that's because it is. 720p is 1280x720 in square pixels, and 1080 is 1920x1080. For the footage to fill the frame you'll need to stretch it to fill the frame. Use the Modify -> Conform to Sequence command to make the footage fill the frame. Your footage will be a bit softer, so you might use a mild sharpen, or add a touch of grain to the footage.

As for the color temperature shift that's either because the white balance on the camera changed or the lighting changed. It could be as simple as clouds rolling through, a light being gelled, or using auto-white instead of manually setting the white balance. If you've set the white balance and the lighting isn't changing the color won't change, unless there's some crazy jank going on with your equipment.


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Fernando Bobadilla
Re: 1080p and 720p in the same sequence/video
on Mar 11, 2012 at 4:06:37 am

Thank you, Jeff; I really appreciate the support.

As for the "Use the Modify -> Conform to Sequence..." process, is that in FCP or Cinema Tools?

I think I know why I'm thinking the color temp/darkness has changed: because when I shoot for slow mo, I crank the shutter speed to about 250 or a little more which darkens the visuals.

I was taught in school to shoot 1080p with a shutter speed of about 80 to 120 or a little more.

Should I just shoot 1080p with the same shutter speed as the 720p? Because if that's not the case, I know I'm going to be mixing and matching lighting between the 1080p takes the 720p takes.

I'm going to download Cinema Tools ASAP, and Twixtor as well - unless they do the same thing - I should be on my way to success..

Thank you very much and bless you.

Fernando


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Jeff Meyer
Re: 1080p and 720p in the same sequence/video
on Mar 11, 2012 at 4:51:31 am

I want to throw this out there first - to "conform" is to make something comply to standards. We're using it for two different things in this conversation.

The Modify -> Conform to sequence command in Final Cut adjusts the video to match the sequence.
The Conform process in Cinema Tools changes how the file is played back.

Cinema Tools is an application that comes with Final Cut Studio. You should consult your Final Cut installation discs if you don't have it installed. Cinema Tools changes how the file is interpreted, so the 60fps is played at 24fps. Cinema Tools will do the speed transformation instantly.

Twixtor is very, very different. It analyzes the motion in the file and creates intermediate frames.

===

Considering shutter speed, the most film-inspired frame rate to use on dslrs is 1/50. At 24fps with film each frame occupies 1/24th of a second. Half of that time is spent being exposed (1/48th of a second) and the other half is spent moving in/out so the previous and next frames can be exposed. With digital the temptation is to use the shutter as an exposure balancing tool, but it changes the visual quality of the motion. Things that are moving have a certain amount of blur at 1/48th of a second that the viewer has come to expect from years of seeing 1/48th of a second as the shutter speed. When you shutter up to 1/100 you cut the blur in half, and things don't have a "natural" amount of motion blur.

With film cameras the shutter speed is considered an angle due to the rotary shutter. 1/48 is considered a 180º shutter at 24fps. 1/96th would be a 90º shutter.

Personally, I have a background that involves sports, so I'm not too crazy about keeping a 180º shutter. We tend to shutter up to create sharper, more pronounced motion. It's great for replays. When you get into narrative work you'll find the shutter is fixed at 1/48th, or 1/50th if you're shooting SLR. Where your teacher/professor got 1/80-1/120 I'm not sure. Perhaps they were trying to compensate for not having ND filters available to balance the exposure.

===

With the 180º shutter angle concept established, it's important to realise that slow motion is a special effect shot. If you want to give the impression of time slowing down shutter up, use 1/250/ 1/320, 1/5000 to freeze the motion. If you're feeding it into Twixtor or Motion's Optical Flow the faster the shutter the happier the software will be, because having hard edges on things that are moving allows it to do a better job of making more frames. If you're using Cinema Tools exclusively you might avoid the extremely high shutter speeds, otherwise it will look very, very choppy.

===

When you change the frame rate, you need to adjust your lighting or other elements of exposure to compensate. When you go from 1/50 to 1/125 you'll need to more than double the light. Either add more light, open the lens up and keep an eye on what's in focus, or ISO up knowing that the image will be more noisy. Just like there's no such thing as a free lunch, you can't change only the shutter speed and expect the image to look the same.


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Fernando Bobadilla
Re: 1080p and 720p in the same sequence/video
on Mar 13, 2012 at 1:00:15 am

Thank you very much!

So, I'm assuming that I shouldn't assume that Cinema Tools and Twixtor both can give me the slow motion that I want, correct?

I'm certain that it's Twixtor that'll give me the slow motion effect that I want for my music videos - I'm still uncertain about what Cinema Tools does besides make FCP accept the different frame rate of 60fps when my other footage in sequence is 1080p/24fps..

Also, what do you think is a better fps to shoot at: 1080p 24fps or 1080p 30fps?

Thank you, sir.. I appreciate your time,

Fernando Bobadilla


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