Help with 24fps and jitter

[human001]

hi,

I seem to be getting jittery footage only at 24FPS and 48FPS.

I kinda have an understanding of ND filters, but I am here to see what the general consensus is on this. This test/comparison is with no ND filters.

Here is a link to the footage:

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The above is 24FPS, 1/500, ISO100
No ND filter, just raw footage off the drone. Note how it actually jitters.

Here is the exact same settings, except at 30FPS:

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The above has zero jitter.

First, why would the 30fps have zero jitter but the 24fps does?
Furthermore, I get the same jitter effect at 48fps.

60fps looks good. Ive not checked the others.

I'm lead to believe that 24 and 48 must require some sort of "smoothing out" with an ND filter... but I'm not 100% sure. It seems like those jittery frames need motion blur to fix them.. but then why would 30fps be so different?

Will an ND filter take care of this? Will the 30fps (and 60fps) benefit then, with the proper filter?

I only have the ND filters that came with the air 2 combo (16/32/256 or whatever) ... earlier today I was messing around with ND16 at 24fps and the footage was still jittery. I think the camera was at 1/50.

Is this a bad cam, or a normal drone issure, or does it require ND.

Also to note, I'm using the scandisc extreme pro 128g (black and red) and I just built this computer over the summer, 18core i9, 128gig ram and RTX2080 super vid card. All previous footage Ive taken was at 60fps, this is the first time I'm discovering the jitter with 24fps.

heh, whoever takes the time to break this down and answer.. thanks =)

 

[Joe Foreman]

The simple answer is your need to set your shutter speed to twice that of your frame rate, so:

24fps = 1/50th (I don't think there is a 1/48th so this is the next closest)
30fps = 1/60th
60fps = 1/120th

Then adjust your exposure by using your ND filters (or ISO but I'm assuming your trying to make the image darker if filming at 24fps during the day so you want to keep the ISO as low as possible, being 200 ISO)

The shutter speed becomes less important as your frame rate goes up and/or the speed of your movement goes down.

So for filming in 24fps mode a 1/50th shutter speed = slow movement of drone, or gimbal, is the best way to avoid jittering.

Hope this helps.

 

[human001]

Thanks for the reply.

I do understand most of the ND filter usages, however, I'm concerned with the slight jittering at 24fps.

I got out the morning and shot this:

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It was shot at 24FPS, 1/50 and ISO100 using an ND16

I still see jitters/stuttering in the trees. Pretty much everything from mid-frame and below.

I also shot further tests and I still see the jitter. The other tests were:
24FPS 1/50 ISO100, normal mode, ND16 = jitter
24FPS 1/50 ISO100, sport mode, ND16 = jitter

30FPS 1/60 ISO100 cine, norm and sport mode, ND16 = all smooth

50FPS 1/100 ISO100 ND16 = smooth

Am I just seeing things here, or is this a normal product of 24fps with drones and somewhat fast movement?

 

[Kilrah]

24fps will always have jitter when displayed on a computer display that's running at the standard 60Hz since it's not a whole multiple. You need a display set to 24Hz refresh (or a whole multiple of it) for it to show correctly.

30fps happens to be half of 60 so each frame is just displayed twice, but 24 isn't so the computer has to show some frames too early and some too late to align with the display refresh and that's what looks jittery.

Doesn't matter if the footage comes from a drone or anything else.

 

[human001]

Ah ok that makes sense now. I never considered the refresh rate. This would explain jitters at 24/48fps.

Thanks

 

[hiflyer201]

Truthfully I didn't see a jitter on my monitor.

 

[Joe Foreman]

Thanks for the reply.

I do understand most of the ND filter usages, however, I'm concerned with the slight jittering at 24fps.

I got out the morning and shot this:

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It was shot at 24FPS, 1/50 and ISO100 using an ND16

I still see jitters/stuttering in the trees. Pretty much everything from mid-frame and below.

I also shot further tests and I still see the jitter. The other tests were:
24FPS 1/50 ISO100, normal mode, ND16 = jitter
24FPS 1/50 ISO100, sport mode, ND16 = jitter

30FPS 1/60 ISO100 cine, norm and sport mode, ND16 = all smooth

50FPS 1/100 ISO100 ND16 = smooth

Am I just seeing things here, or is this a normal product of 24fps with drones and somewhat fast movement?

To my eyes this is normal amount of jittering for 24fps at that speed and subject matter, whether it's acceptable to you I think is a preference at this point.

I agree with the point about the monitor you're viewing it on making a difference. I find the same footage can look significantly different depending on whether I'm watching it back on an LCD vs Plasma vs DLP Projector. There are so many variables at the end of the day it's what you (or your client) find acceptable.

Ultimately you want this whole process to be enjoyable and if you find you can't focus on the pleasures of flying @ 24fps due to the perceived jitters, maybe it's not the right format to be using?

 

[jowlymonster]

I must be going blind as I couldn't see any difference in the clips and I'm not sure what jitter you're referring to!

 

[Yogi053]

I must be going blind as I couldn't see any difference in the clips and I'm not sure what jitter you're referring to!

Same here, then again, my eyes are 26 years older than yours!