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TOPIC: 120fps slo mo????

120fps slo mo???? 18 Jun 2018 02:50 #95974

  • Jonathan Levin
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Hi all.

I have a Nikon D850 that has the ability to shoot up to 120fps slo mo. There is very little info on the web or even Nikon, but I found this if it will help further on:

“The Slow Motion modes will save the file in a compressed 30p, 25p or 24p wrapper for 4x or 5x slow motion for easy editing on the timeline. We like that they skipped 60fps which is what many slow motion cameras end up with. You start at the slowest possible factor in 24p if needed without the need to re-interpret the footage on the timeline.

Slow-motion: Full HD 1,920×1,080 30p (x4) 120fps
Slow-motion: Full HD 1,920×1,080 25p (x4) 120fps
Slow-motion: Full HD 1,920×1,080 24p (x5) 120fps

So I have been testing this. I set up the camera to slo mo 30p, (as shown above) I see that thevideo is actually being shot in 60p.

I then add that video to FCP project (30p), set the retime to Automatic, and then as expected the video is 50% or slo mo. Can any of you figure out how to get 120fps as Nikon states? There is no 120fps setting on camera. About the only thing I can think of is that maybe it is a different retime setting within FCP. All new to me.

Any ideas? I have an email to Nikon but thought I’d get your expert advice.

Thank you.

Jonathan
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120fps slo mo???? 18 Jun 2018 03:14 #95975

Jonathan Levin wrote:
… There is no 120fps setting on camera. …

according to your cams manual, there is:
onlinemanual.nikonimglib.com/d850/en/06_...l#slow-motion_movies
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120fps slo mo???? 18 Jun 2018 17:40 #95980

  • Jonathan Levin
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Hi karsten.

Since my last post here I've learned a few things. My initial tests were done with the camera connected to an Atomos Ninja Flame with the camera set to "Slow-motion: Full HD 1,920×1,080 30p (x4) 120fps"

The resulting file from the Flame was a 60p (according to inspector) clip and did in fact play in the project in slo mo., once I changed the retiming to "Automatic". The clip header in timeline says "50%"

I think this may be an issue with a connected external recorder for some reason. More on this in a bit.

I contacted Nikon, and they said that the camera actually records 120fps in in camera in "Slow-motion: Full HD 1,920×1,080 30p (x4) 120fps" mode,

I decided to run a test WITHOUT Atomos connected, placed clip in Project, and that file DID play much "slower" than my test with the Atomos. I dod not have to retime clip. Even when I selected "Automatic" in retime, the only thing I think that did was cause the clip to need rendering and nothing else. So I chose normal.

So the bottom line is for 120fps, you have to record to the D850's internal camera card (XQD) to achieve said slo mo.

I was hoping to take advantage of full slo mo sensor output from Nikon to Atomos for slo mo, but it appears that set up is limited. I can retime the Atomos 60p, but it looks kind of cr@py , and appears to double some of the frames.
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120fps slo mo???? 18 Jun 2018 22:15 #95984

  • haysoos123
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Have you checked what the Atomos is set to record to? According to what you said, it's spitting out 60p, when you should be setting it to 120p. Whatever the camera is outputting isn't necessarily what the Ninja is recording. The reason why the Atomos 60p looks bad is because it threw away half the frames, and you're still trying to slow it down 4x. One thing you have to check is whether the Nikon is even capable of sending out 120fps through however you're connecting it to the Atomos (HDMI probably?).
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120fps slo mo???? 18 Jun 2018 22:26 #95985

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Forgot to mention that it's also possible that the camera is recording 120fps and outputting all the frames at 30p, in which case you want the Atomos to record 30p and not 60p. If it's recording to 60p it will double every frame, which maybe also what you're seeing.
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120fps slo mo???? 18 Jun 2018 22:42 #95986

  • Jonathan Levin
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Hi haysoos!

Thanks for that. I have learned a lot more since my last post and you are spot on about some of the issues.

In addition to getting in touch with Nikon, I also talked to Atomos. One of the first things that was brought to my attention is hdmi, which is how I connect camera to recorder, is only capable of handling up to 60fps., at least with current firmware for the D850. So that is why files recorded with my Atomos come in at 60p. And that looks good , until you try and “stretch” that clip a bit or add Optical Flow.
The camera as it records to internal card IS recording 120fps and appears as it should in a 30p project. The downside is those files are your typical compressed h.264 flavor. In order for me to get a higher frame rate a set up going from sdi-hdi(?) to a recorder that has the same i.e. one of the Atomos units with that connectivity. Hdmi does have it’s limitations. I suppose for now if I don’t want compressed video, I could just use the 60p from my Atomos...provided, like you said it’s not adding or subtracting frames. Another test, another day.
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120fps slo mo???? 18 Jun 2018 22:48 #95987

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Yes the camera is recording 120 and output is 30. I have to check to see if I can change the frame rate on the Ninja Flame. I have a feeling that setting is set by the cameras output signal. I’ll check that out though. Thanks again.
Last Edit: 18 Jun 2018 22:48 by Jonathan Levin.
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120fps slo mo???? 21 Jun 2018 04:04 #96017

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Most external recorders that I have used do not modify the frame rate of the incoming signal either thru SDI or HDMI, so I suspect your camera has options for the output signal based on your recording mode. If your cameras output is fixed at something lower than 120fps when internally recording 120fps you are probably better using the cameras H.264 recorded files....you might find the quality to be sufficient, especially for web delivery.
Creating history....one edit at a time !
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120fps slo mo???? 21 Jun 2018 20:48 #96023

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Thanks DG.

There isn't a way to change the frame rate on the Nikon in any of the Slo Mo modes. I have not had a chance to find out if I can change the signal the Atomos is receiving from 60p to 30 p. I have a feeling that this won't work, since hdmi supposedly isn't capable of of recording in this mode.

So I think like you said for short b-roll stuff, the h.264 files should be ok. More experiments later.
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