GH2 24p Cadence "judder"...

[William Hohauser]

A couple of 24p judder tips:

There is a certain speed of camera movement that causes noticeable judder. It has to do with the visual information moving past the sensor in relation to the frame rate. A slightly slower pan will fix this but also a quicker pan can also reduce judder. You can get judder in 30p but as the frame rate increases the exact pan speed where judder is caused is reduced. And when it happens, it's less pronounced. At 60 frames per second (progressive or interlaced), judder is essentially eliminated.

Seeing judder also has to do with the perceptions of the viewer. The same pan rate on a landscape that produces disturbing judder will not have the same perceived problem if there is a person walking at the same pan rate in the center of the shot. The attention is on the person not the landscape especially if the person is close to the camera.

Compression sometimes reduces motion blur which increases the appearance of judder.

[Jeff Harper]

Right William, when following a subject, the background blur is not important.

I watch feature films shot on film and they all look the same, when following a subject the background looks like crap, but I only notice it because I'm looking for it. When I'm immersed in the film, though, I don't notice it. On the other hand, wide establishing shots, particularly outdoor shots, shot in film, will look relatively "bad" when they pan, there is no way around it, apparently. That is why they so rarely pan for those shots, I'm sure.

Question William: it would seem obvious, but I'm not sure. When doing a "moving" shot in 24p, where the camera is moved by hand or steadicam to get a shot, say of a bride's dress or of anything else, the judder problem will be no different, or will it? Is there a technique for doing moving shots that minimizes the problem?

[William Hohauser]

There might be a tracking speed that is not good for certain shots but as I understand it (and experienced it) judder is more obvious on steady pans or tilts than erratic hand held shots.

I forgot to mention that shutter speed is an important factor as well. Since cameras like the GH2 do not have a true film shutter speed but decimal increments, judder will happen in very slightly different circumstances. And a high shutter speed, which we might be tempted to use as a way to force DOF, can cause really disturbing judder in pans and action shots. Once again, following a subject reduces the perceived judder.

[Jeff Harper]

Thanks William, it's interesting that moving shots are not as affected. I do few moving shots and very little handheld, but's it's nice to know that it is not so bad as a pan. Good stuff, thanks. I thought I had seen some very elegant moving shots in 24pm but can't remember specifically.

[David Grinnell]

Also I don't think this was posted but having the shutter speed at 1/30 helped my footage out a ton as movement blurs instead of juddering along like you have shown...

[Steven Bills]

David, can you post some 1/30 tests?? Is it obvious that the SS is a lot slower?

I think some of the problem might be shutter speed. Maybe a hack with 1/48 would do the trick?? Because currently we have only 1/50, which equates to ~172 degrees, whereas 1/48 would be the real 180 degrees...

SB

[Sanjin Svajger]

I'm sorry guys but the video posted on vimeo looks bad. And that IMHO has nothing to do with progressive shooting. Pogresive definetly doesn't look like that. The judder in that video isn't consisten by far. Progresive judder should be consistent not on and of like this. And progressive judder looks a lot different then this. I just might go this far as to say that this is not progressive judder but it looks like droped frames. The video in the video stops for a moment a couple of times. That to me

Seriusly, am I the only one seeing this?

Have a look a this Alisters video: Progressive v Interlace and using the shutter to reduce motion blur - YouTube
@Steven: do us a favour and do another pan, and this time do it evenly. Put a rubber band on the handle of your tripod and pul on it. This will produce the most even motion without unwanted jerks. Like this: Best Camera Trick Ever! - YouTube
Then upload that again and give us the link. Also it would be best to look at the video in a NLE. Before vimeo compression.

[Don Litten]

No, I see it also but I'm not sure what to make of it.

William, if you do another test shot you can upload the native file to Vimeo. They will still compress it but the original file is not compressed and can be downloaded. We can view it that way.

[Pat Reddy]

I have tried 10 to 20 flavors of the hack so far, and some seem more likely to have this dropped frame look than others. I would recommend trying some of the hacks that have been released in the last two weeks. Also, the behavior of the camera may be affected by the lens you are using. Panasonic lenses with OIS are demanding more of the GH2's processor time for OIS and lens correction calculations, and the hacks push the processor to the limit. Some of the hacks, for reasons I don't understand, are choppy for the first few seconds of filming before they reach full data rates. You can see this if you analyse the files in Streamparser. Finally, the Panasonic OIS itself can often exhibit jerkiness. If you shoot with a non Panasonic lens and select the "shoot without lens" option in the menu, the GH2 will have a little bit more cpu available for the hack.

The various hacks and patches really boost the capabilities of the GH2 but none of them are without their limitations. To get the best one(s) for your purposes can require a lot of trial and error and may still mean that you have to adjust your shooting style to minimize problems. I have been able to get very smooth 24p pans. The hack I have used the most is the old Aquarius 2. I would recommend a specific newer one, but I have been trying so many I would have a hard time remembering which one is best for this. I'm still waiting for a really good HBR patch for 30p that will work on my Sandisk Extreme 30mbps cards and can handle busy natural scenery well.

Pat

[Andrew Rowe]

@Sanjin. Steven said the pan was smooth. It looked worse to me than 24p judder, which is why I mentioned the image stabilization early on, but the extra nastiness could be down to compression/streaming. Did you try turning off the image stabilization, Steven?

The difference between 1/50 and 1/48 is very slight and most UK features (X-Men: First Class, Kick Ass etc) are shot at 1/50 (with 172 degree shutter) to cope with the 50Hz mains frequency. If movement in features (and progressively-acquired PAL TV/video for that matter) were as bad as all that, then I don't think 24fps would remain the world's dominant, standard frame rate.

[Andrew Rowe]

Steven said the pan was smooth. It looked worse to me than 24p judder, which is why I mentioned the image stabilization early on, but the extra nastiness could be down to compression/streaming. Did you try turning off the image stabilization, Steven?

The difference between 1/50 and 1/48 is very slight and most UK features (X-Men: First Class, Kick Ass etc) are shot at 1/50 (with 172 degree shutter) to cope with the 50Hz mains frequency. If movement in features (and progressively-acquired PAL TV/video for that matter) were as bad as all that, then I don't think 24fps would remain the world's dominant, standard frame rate.

[Chris Medico]

Rolling shutter magnifies judder.

[Sanjin Svajger]

@Andrew: yes. I didn't saw your post. I'm totally beat today so I just scrolled over the thread and gave a very quick reply. As you can see from the writing:)

Anyway, this in not progressive judder. It's something else that can be almost 100% fixed. As all of you stated before; this hacks are a hassle. Does that judder happen when using the original firmware? I think that installing the original firmware and repeating the test should be your first logical step in figuring this out.

[David Grinnell]

Here is my 24p panning at 1/30 shutter speed...

https://vimeo.com/38248835

[Don Litten]

David, is that a hack or stock?