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QuickHitRecord

Camera Cadence/Motion

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Like color science, cadence/motion can differ greatly from camera to camera. It's harder to spot and consequently it's not frequently discussed. But some cameras have 24P that looks an awful lot like 30P. So, strictly focusing on c​adence, which cameras look good to you, and which don't? Please post examples.

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I'll go first. 

 

I bought and then sold my FS100 because I thought that the cadence looked all wrong to me. Here's an example (not shot by me), which in all other respects looks good to me: 

 

 

On the other hand, I think that the hacked GH2 has great motion cadence:

 

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Guest Ebrahim Saadawi

I hear this term thrown many times on the forums but never seen an actual description of what it means. Even after searching. 

If two cameras take the same number of frames each second, and each frame is exposed for the same amount of time: wouldn't motion look 100% identical?

What's that "cadence" people speak of? 

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I don't like it on the d800, but on the canon 50d with ML hack it looks good (strange considering that the 24fps mode is just some sort of hack as the camera only does 30p). When you shoot h264 on the same camera it looks horrible so my guess it's something related to the encoding process.

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I hear this term thrown many times on the forums but never seen an actual description of what it means. Even after searching. 

If two cameras take the same number of frames each second, and each frame is exposed for the amount of time: wouldn't motion look 100% identical?

What's that "cadence" people speak of? 

 

If you watch the examples above, are you able to see the difference? It's easiest to see when there are people in motion on screen, at least for me. I'm not entirely convinced that anyone and everyone is capable of seeing it, just like some people can see more colors than others, and some projectors give certain people headaches. 

 

And it's equally tricky to define, but I'll try. It's how a camera captures motion, which I believe pertains to the amount and characteristics of frame-by-frame motion blur (i.e. shape of blur, opacity of blur, etc.). But I suspect that it might be something on top of that as well.

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it's mostly codec implementations that do this i reckon.

 

Since non i-frame codecs dont display individual frames, motion is usually more "smudged". All Sony cams look like this to me. Things like AVCHD are taking one complete image, then making, lets say the next 12 or so, by altering the full, or "I" frame. Oddly, the C100 is AVCHD but has great cadence.... there's always an exception ;)

 

Raw streams and ProRes streams tend to look great motion wise, but they're more like individual film frames, so they would.

 

It's often down to taste, I wasn't a fan of FS100 or GH2, but liked even the 550D, somehow I think Canon nailed it. RAW and I-frame codecs get rid of most of this issue though. 

 

Then it comes down to other factors, like colour and just the overall "look".

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When shooting 60P there are no cadence problems. Motion looks always good. It is a pity that all video systems and delivery methods are not there yet.

 

Arguable. But the arguments are hard to nail down. My Apple TV plays iTunes movies (indeed, as it seems, everything) as if filmed with higher frequency (like the 200Hz TVs). The images then look very clean and clear, but actors, even great actors suddenly can't convince anymore.

 

Also small movements sometimes look slightly sped up, but very fast movements (car races) lack any momentum.

 

Before he published his HFR Hobbit, Peter Jackson said you would get used to it within five minutes. Maybe. You get used to it because you eventually start to follow the story, but I for one will never forget it completely. For me it's irritating, for others not so much. Some see the 'clarity' aspect and say it's better. Different people have different perception.

 

This FS100 motion looks clearer to me than my BMPCC. I do see some barely perceptible judder. Maybe I'm just too much used to it as a long time cinema projectionist. This is becoming esoteric.

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I hear this term thrown many times on the forums but never seen an actual description of what it means. Even after searching. 

If two cameras take the same number of frames each second, and each frame is exposed for the same amount of time: wouldn't motion look 100% identical?

What's that "cadence" people speak of? 

 

I agree with you that the term cadence is somewhat confusing: In fact, I would I'd dare say that most of the "cadence" problems do not exist. They are simply a question of footage not properly shot or encoded.

 

Many, many videos on the web use fast shutter speeds in sunlight to compensate the lack of an ND filter, causing an akward cadence.

Some others use a very slow shutter speed in low light to compensate the lack of proper lighting, causing an akward cadence.

Some in camera codecs record "fake" progressive framerates that are actually interlaced or the footage is interlaced-deinterlaced in the NLE to fit a certain standard, causing an akward cadence.

Some other times, 23.976 footage is edited and encoded as 24p, which is not exactly the same.

And finally, some other times it's the players fault (though I don't own an Apple TV) or the encoded stream, or any of the absurd TV "image enhacements" of any recent TV set.

 

Under normal circumstances, any professional camera recording true progressive footage at a proper 180º shutter angle should yield that cinematic motion. And I can include DSLRs and midrange cameras, too. You don't see those "cadence" problems when you go to the movies, even though you see movies recorded (not filmed) with a mix of Alexas, Reds, C300s, C500s and even 5Ds. Because the footage is properly shot, conformed and handled throughout the whole workflow.

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If you watch the examples above, are you able to see the difference?

 

Are they shot at the same frame speed? Is the shutter speed exactly 100% the same? Is the contrast in the shots the same? Is the encoding the same (are you watching the same quality h264 files? Nope, one is Vimeo, other one is Youtube, encoded into them god knows how)

 

Even motion that's EXACTLY the same will look different depending on the contrast of the scene. I don't buy this "different cadence" hogwash. The only difference in motion nowadays is the amount of rolling shutter (which is very important though)

 

When people do 3d animations INTO scenes shot with high end cameras vs low end cameras, is the motion rendering different? Nope as long as the rolling shutter is the same. I don't think ANY highend software has any settings for motion cadence except motion blur. So what is this "magic" people keep referring to?

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The motion cadence on blackmagic cameras is superb.

 

It does look good, from everything I have seen.

 

Oddly, the C100 is AVCHD but has great cadence.... there's always an exception ;)

 

Raw streams and ProRes streams tend to look great motion wise, but they're more like individual film frames, so they would.

 

I think that the C100 is a winner here as well.

 

And maybe you're onto something with the intra-frame argument, because I think that the stuff I've seen from the Magic Lantern raw cams looks pretty good as well.

 

Are they shot at the same frame speed? Is the shutter speed exactly 100% the same? Is the contrast in the shots the same? Is the encoding the same (are you watching the same quality h264 files? Nope, one is Vimeo, other one is Youtube, encoded into them god knows how)

 

I don't have the tests on my computer anymore, but I was clearly able to see the difference between the way that these cameras recorded motion when I owned both bodies. I did have them set up together at points, recording the same subject with the same contrast. The only thing I may not have been able to match exactly was that the FS100 could record at true 1/48 shutter, while the GH2 was set to 1/50. But the GH2 was the one that looked way better to my eye.

 

The clips that I have posted above reflect what I was seeing with these cameras. I see a difference!

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it's mostly codec implementations that do this i reckon.

 

Since non i-frame codecs dont display individual frames, motion is usually more "smudged". All Sony cams look like this to me. Things like AVCHD are taking one complete image, then making, lets say the next 12 or so, by altering the full, or "I" frame. Oddly, the C100 is AVCHD but has great cadence.... there's always an exception ;)

 

Raw streams and ProRes streams tend to look great motion wise, but they're more like individual film frames, so they would.

 

It's often down to taste, I wasn't a fan of FS100 or GH2, but liked even the 550D, somehow I think Canon nailed it. RAW and I-frame codecs get rid of most of this issue though. 

 

Then it comes down to other factors, like colour and just the overall "look".

 

Those are ALL-I, not just i-frame codecs :)

Every blueray movie we watch has lots of p- and b-frames between i-frames, but you usually don't experience those cadence perception problems. That's just how MPEG works since the DVD days. Or even older Video-CD times.

 

If motion cadence problem is actually the frame jitter, then you can test it experimentally.

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To expand on it, let's take 24 frames or one second at film rate.

 

With film you have 24 full images, motion blur is kept in each image, not smeared netween them.

 

With ML 5D raw, Alexa Pro Res, Red Raw, Blackmagic cameras etc, you have 24 distinct images, individually compressed either losslessly or mildly lossily. Motion blur is kept within each image.

 

With AVCHD and other Long GOP CODECs, the I-frame image is divided into pools of pixels for analysis across time. only some frames are whole, the I frames, the rest refer the different pixel pools to the I frame and usually to a frame in the middle of the group too. In order to remove data the codec only moves what it has to. Your one second may have only two complete images, the rest are created as best can be from the other frames, with huge changes causing pixellation and blocking due to so little data headroom.

 

On top of this, the red-channel resolution is quartered, and the blue channel halved in 4:2:0, so the spatial resolution for movement is cut down, as well as the temporal resolution.

 

In short, the plastic movement you get from many implementations of such long GOP CODECs reflects the methods use in compression.

 

Motion blur is also smudged and blurred by chroma sub-sampling (4:2:0:) and by interframe compression.

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Those are ALL-I, not just i-frame codecs :)

Every blueray movie we watch has lots of p- and b-frames between i-frames, but you usually don't experience those cadence perception problems. That's just how MPEG works since the DVD days. Or even older Video-CD times.

 

If motion cadence problem is actually the frame jitter, then you can test it experimentally.

 

Yes indeed, I think the problem is capturing and compressing like this. For delivery it 's clearly fine, very efficient in fact and Blu-Ray look ace to me, no such motion problems.

 

Truth is, these codecs were really optimised for delivery... capturing with them is a compromise.

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I'll go first. 

 

I bought and then sold my FS100 because I thought that the cadence looked all wrong to me. Here's an example (not shot by me), which in all other respects looks good to me: 

 

 

To me it looks like a combination of a terrible image stabilisation (especially when she walks @0:24) and slow shutter speed. So when the camera is handheld, every second you get a smooth motion followed by a hard drop - not very pleasant.

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