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Redshift camera jitter during horizontal camera move


pfistar

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Greetings everyone - 

 

I'm wondering if this is a common problem:

 

In this video, between 00:09 and 00:14, and to a lesser degree, between 00:21 and 00:29, there is what appears to be some jitter or staggered movement as the camera pans across the subject. As far as I can tell, all the motion blur settings are turned on, but perhaps I forgot something? I've also been told it might be a frame-rate issue. In any event, I'm wondering if anyone else has had this problem and if so, how did you resolve it.

 

Many thanks, NpF

 

 

 

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I've had a similar problem once, and it was fps-related.

 

My C4D-scene was setup with 24 fps. I rendered it as an image sequence and imported that to Premiere.

 

The Premiere project setting was also 24 fps. BUT! When I imported my rendered image sequence, Premiere decided to interpret it as 25 fps -- introducing a very similar amount of jitter as shown in your video.

 

The solution: After importing the image sequence into premiere, go to your project bin, select the clip, rightclick and search for "interpret footage as" (or something similar). In the dialogue, select your correct fps. Only after doing this, use the clip in the timeline. 

Now everything should be smooth as butter.

 

I guess, the same solution applies to other apps than Premiere as well.

 

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You really have a whole host of FPS-related problems in that video

0:09 Here you have 2 problems. The most obvious one is the constant flickering from one frame to the next. This is caused by a combination of the camera motion and a lack of motion blur. Motion blur would largely fix this, but then of course youll have a much softer animation. The real answer here is that this simply isn't a shot you should do on low fps projects (24, 25 30fps)

 

The second problem here is that you have a 24/25 fps mismatch. Once per second the camera skips an entire frame, this usually means you have rendered at 24fps, but your editing app is trying to stretch this to 25 fps.

 

0:22 Here you have a different fps mismatch. You can see the image jumping 4-5 times per second, this tells us that there is a 24/25 to 30 fps conversion problem.

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  • 2 weeks later...

@KEPPN @IMASHINATION

 

Thanks to both of you for your responses. 

I did some back-checking to see if there was indeed a frame-rate mismatch between my C4D output, and my editing app (in this case it was After Effects, which is what I usually use with any piece shorter than 3-4 minutes).

 

In any event, I double checked my project settings and output settings in C4D - 

  • I’m certain everything was set to 24 fps at render time

  • I’m not sure there’s any other parameter that would effect output framerate, besides that which is in the Project Settings panel and that which is in the Render Settings panel, but I’d love to know if I’ve missed something here

  • It’s worth noting that my original output had some Redshift motion blur at a low sample setting

I also double checked project settings, import preferences, and composition settings in AfterEffects

  • Again, every setting was at 24fps at import time in every case

  • All Comp settings and output settings were set to 24fps

  • It might be worth mentioning that my output format has always been .mov Quicktime with H.264 compression, though this might be irrelevant

  • I did try a re-import just in case, but result was the same as far as I can see

  • It’s also worth mentioning that the jittering has always been quite pronounced whenever I’ve done RAM previews in AE

  • In the case of both shots in question, I did use a slight linear time remap (96% in the case of shot01 (0:09)  and about 90% for shot02. I re-rendered from AE after removing the time stretch, though it didn’t appear to make much difference in terms of reducing the jitter.

 

@IMASHINATION - Taking your advice about rendering out of C4D at double frame rate. I’ve done a few tests - starting with re-rendering the scene at 48 fps, with a slight bump in motion blur sampling.

 

I then imported this into AfterEffects with a 48 fps import setting, and brought it into Comp also set to 48 fps. 

 

  • I then rendered the clip out from AfterEffects as an .mov file at 24 fps. There’s still a little bit of jitter, though it’s less pronounced than before.

  • I re-rendered using frame blending at the second setting, again at a 24fps .mov output  and this made jitter even less pronounced.

  • Finally, I did a third re-render, again at a 24fps .mov output using ReelSmart MotionBlur and that makes the jitter virtually undetectable!

 

@IMASHINATION - Questions for you, since you appear to have some knowledge on the topic:

  • Is this issue generally common with scenes that have lateral camera motion and a lot of parallel vertical elements?

  • Why render at 2x FPS (in this case 48 fps) from my 3d program, if my final output (from AE) will ultimately be 24fps? Don’t half the frames get dropped anyway, or is there some kind of resampling that happens at render time in AE?

 

Thanks again to both of you for the response.

NpF

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Sorry, Im not sure I can see where anyone suggested rendering at double the frame rate?

 

Outside of the framerate mismatches, what you're trying to show on screen just fundamentally will not work on a low framerate project. You're moving a large, crisp, detailed object across the screen at too high of a speed. This means the model is jumping ~100 pixels per frame. This happens in 3d and real world camera footage, it isnt limited to 3d rendering. Ways to fix this:

 

1) Use a higher framerate project, and by this, I mean higher for everything including the final delivered product. You can't just render it high, then chop it back down to 24fps again. If the object moves 100 pixels per frame on a 24fps project, then it would only move ~35 pixels per frame in a 60fps project. But of course all your rendering and editing gets slower because now you have more frames

 

2) Use motion blur. I can see your renders do have motion blur, but the settings arent high enough for the movement. On this project you need a 180 degree shutter, or about 0.02 seconds (1 second, divided by 24fps, divided by 2 (for the 180 degree shutter angle)) of blur per frame in order for it to look natural. Less than this and it will flicker, higher than this and it will smudge.

 

3) Slow down the camera movement. Lower movement = less stuttering

 

4) Change the camera movement. Your zooms are fine, because even though the camera may move quickly, visually everything just gets a few pixels larger or smaller. Same for rotations, theyre fine because the object isnt moving across the screen. Only pans and tracks will strobe like this.

 

Someone had a similar problem a while back, maybe this helps demonstrate the issue more. Unfortunately their links now problem, but it had the same strobing as they panned the camera left to right

 

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  • 2 weeks later...

@imashination

 

Thanks for the reply & for waxing some wisdom on the topic. It was frankly something I never knew that as a general rule of thumb one should avoid fast camera movement past a subject with vertically oriented lines. At the end of the day, I found the most workable solution to be post-production blur (in this case RSMB in AfterEffects). Not quite photographically accurate, but close enough.

 

As to your comments:

 

"Sorry, Im not sure I can see where anyone suggested rendering at double the frame rate?"

On 6/4/2022 at 8:19 AM, imashination said:

The real answer here is that this simply isn't a shot you should do on low fps projects (24, 25 30fps)

Since my baseline was 24fps, it seemed logical to me for this to mean that doubling original fps would make sense, (rather than setting framerate at some arbitrary number). That said, in general, non-film/tv-legacy-based frame-rates are more often than not out of budgetary range for most of my projects.

 

"2) Use motion blur. I can see your renders do have motion blur, but the settings arent high enough for the movement. On this project you need a 180 degree shutter, or about 0.02 seconds (1 second, divided by 24fps, divided by 2 (for the 180 degree shutter angle)) of blur per frame in order for it to look natural. Less than this and it will flicker, higher than this and it will smudge."

 

I appreciate your explaining this with a bit of mathematical formula. I'll definitely be bookmarking this for future use!!!

 

Thanks again,

NpF

 

 

 

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