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GH2 Stutter/Judder/Strobe issues discussion
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  • Matt, thanks for the input. I actually do that on some monitors. Don't take this the wrong way but I work work with footage, from different cameras, everyday. Been doing it for years. I know what 24p looks like. I'm not here to debate that in any way. I, and a few others, believe there is something a bit off with this particular camera. That's all. No big deal. It's a consumer product. What do you expect?

    I've been editing a civil war documentary on and off for a company over the last year or so. They started out with Canon xha1 cameras, I believe. The project was already picked up and just needed to be finished. Three quarters of the way through they had purchased a few GH2s and started using them as well. Now, battle scenes have a lot of movement. 24p looks pretty bad in that scenario anyway but the GH2 footage was dreadful. Actually to the point of one of the executives saying that he thought he was going to have a seizure. This was on a state of the art projection system, by the way. You could clearly see the difference. They came back to edit the footage and we decided to take all the GH2 stuff out. Next showing went off without a single comment and everyone was pleased. Except for the filmmakers who lost a lot of good scenes. Now, I know I didn't put one piece of technical information in this story but that's the way it went down. There was no comparison between the two when you saw it projected.

    I have no faith in the GH2 as is. I do have faith in the incredibly smart people working to hack it. From what I have seen, I do believe you could shoot and sell a movie with this camera. You would have to keep motion to a minimum compared to most others. Like I said earlier, most of the footage people are drooling over are static shots. They look great. Just not going to cut it in real business of selling your movie if it has a lot of movement, that is.

    Realistically, I doesn't bug me that much. I'm just another cheapskate looking for an inexpensive movie camera. But, I love the idea of the hack. If there is no way to overcome the look of the motion then I'll just pitch it and move on. Already did that with my first GH2. Just picked up another to see how the hack might affect it. So, sorry to disagree and I appreciate your help.
  • Loaded a few more stable hacks and ended up with the same results. Went back and changed my monitors to 48hz just to make sure. Looks the same. You can see it in the actual lcd on the camera anyway. I read on another post that the motion looks like old Charlie Chaplin films. I think that's a good observation. Though not really what's going on. Anyway, I haven't gotten any real response as to how the hack might alleviate this so I guess there is no real answer right now. I'm sure there will be more info in time. This topic always turns in to the same old " Hey buddy! That's what 24p looks like" type thing so I don't want to press it. So best of luck to you all and thanks for the responses. This is such a neat project so I hope it yields fantastic results down the road. I'll gladly pick up another Gh2 in the future if things in this arena change for the better. For now, this camera is just not ready for prime time. Though I know you can make a good film with any camera. Blah, Blah, Blah. ( Want to avoid the same tired arguments. )
  • @Dalefpf

    I hear what you're saying. I thought the motion of the GH2's 24p mode was poor from the start, and that comment in the manual about "after-images" was just weird. My first impression was that the LCD and the footage both looked sort-of like old silent film.

    Before you give up on the camera completely, can you try one more test? Shoot something using the 80% speed mode, which will give you a true 30 fps recording. Conform it up to 30 fps in your editing software and let us know if you still see the weird judder.

    Also, a reminder that if the shutter speed is longer than 1/25 the frame rate actually drops to accommodate it. You can sometimes inadvertently be shooting at a framerate lower than 24 fps this way.
  • @Dalefpf

    I don't get that is wrong with 24p mode in GH2.
    All that can be different is sensor scan method and speed. It causes jello and other weird things.
    If you are used to CCD or film it is very easy to notice.
    Fast small CMOS cameras can also have fewer jello.
  • @Dalefpf
    There are certain charts published by ASC regarding the judder avoidance. These charts rely pretty much on a "7 seconds rule"
    In a pinch for a 24fps footage shot at 180º shutter (1/50th of a second for GH2, I guess) the panning rate should be such that an object within a frame would move from one edge of the frame to another (left to right or right to left) in 7 seconds.
    One would assume that if you shoot at higher shutter speeds the timing changes accordingly, ie 14 seconds for a pan from edge to edge when shooting at 1/100th of a second.
  • I think there are two issues that affect this: 1) The 60hz refresh rate on most monitors. 24fps will never look right because it has to be telecined - the result is an uneven looking cadence. 2) When the GH2 codec runs out of bandwidth it just abandons encoding macroblocks - the result is that some movement will look like it is changing at a slower rate, like once every 1/2 second. This usually shows up only in parts of frames; you could have grass waving and water moving - the grass waving will look fine but the water flow stutters at 1/2 second increments. Somebody posted a video showing this. The hack helps a lot with this sort of thing.

  • I think the grass looked good because it was covering less space from frame to frame and could be covered by motion vectors. The water moved farther from frame to frame and probably couldn't be covered by motion vectors. At that point the codec probably decided to use intra-frame encoded macroblocks but didn't have the remaining bandwidth to cover them, so the macroblocks were "skipped". I've noticed that with the hack, there are much fewer "skipped" macroblocks than with the factory codec settings.

  • I notice the judder effect in high budget movies (at the theatre) as well, sometimes more so then others depending on the action in the scene or the size of the projection itself. I'm guessing that whether you have a digital projector or reel-to-reel it will always playback at 24 frames per second when at the movies. From my limited experience our eyes cannot differentiate anything above 60fps and even 30fps still looks fairly smooth in my opinion, but 24fps is a motion picture standard. I guess the majority of people don't notice the difference between all these refresh rates and/or don't care.

    To me as long as it doesn't suspend your disbelief or deter your interest, the frame rate game isn't so important if you're not concerned with slow-motion playback.
  • There have been studies that show that the 24fps rate, because it is visible, actually contributes to the psychology of suspension of disbelief. Narrative videos "feel" different at 30fps than at 24fps.

  • Some optical stabilization (antishake) systems could result in stobe-like output during panning.
  • I am wondering if some if this concern actually revolves around the different ways that people convert their original files, and how hard it is for some computers to accurately handle a smooth playback of certain MTS footage. Just an idea.
  • As strange as it sounds, I've noticed a dramatic difference between televisions that have a 240hz refresh rate over those which display at 120. It seems almost "too smooth" or different, at least for a monitor. I'm not completely sold on it but then again I've never had one for myself. Maybe it's force-of-habit from watching last gen televisions.

    Anyways, I think you'll always see judder in certain scenes when filming at 24fps. Your eyes will always catch it if you're looking for it in the first place. When filming at 30fps or higher it's less noticeable if not apparent altogether.

  • For me the issue is not 24p, but whether the 24p on the GH2 looks juddery compared to other cameras like the GH1. To me, the GH2 is very slightly less smooth. I'm sure that some people will see 24p slightly differently than others. For example, some people see rainbows in projection TVs, others do not.
  • There are several separate factors mixed in together in this GH2 judder issue. To those who say "that's just what 24P looks like"
    For that guy, clearly something wacky is going on. But I personally don't think it is anything to do with the camera - it's somewhere in the decode/edit/playback workflow. However for others of us, that clip played completely normally with none of the double image seen in those screengrabs.
  • @Dalefpf

    I agree with you the studder is more pronounced in the GH2 24p footage. Hacked and Unhacked. Shot some steadicam footage with gop3 and about 47mbs the other day. Didn't notice the judder/jitter till viewed on 46" screen. Didn't show up on my 28" calibrated computer screen. Looked at some old GH2 unhacked footage, it was there. Checked some 5D Mkii footage. It wasn't there. When I get a moment, I am going to go shoot some similar steadicam footage on the 5D Mark II to compare. I'm guessing it is going to be there. I may also fire up a projector to see if it shows up there but guessing the same results will show as with the 46" TV. I do not see the judder at 60p nor do I always see it at 24P. I'm guessing it is more pronounced/noticeable during different types of shots/conditions.
  • If I can find the time, I plan to use After Effects to scan the motion of a dolly move and see if all of the frames are moving the same amount. It seems to me that there is some unevenness. I'm also curious whether shooting at 1/60th of a second vs 1/50th. I know that's breaking the rules, but I'm curious if it might work around the overly smeared motion. Has anyone else looked into this?
  • Ran a few more tests today but still no progress. I don't want to come off the wrong way but do you guys really not see the jerky motion and constant strobe when you pan? Regardless of of monitor settings and such. I can see it plain as day on the lcd as I'm filming. I know the proper speeds to pan and I know what 24p looks like. I'll be shooting on a Canon in about 2 hours from now and I'm looking forward to it at this point. The GH2 kills Canon in every way except for this which is so frustrating. I keep boxing this thing up and then pulling it back out to test it again because I'm just so dumbfounded by this. The fact that many people don't complain about this leads me to think I'm crazy. But, I know cameras and do this for a living full time. Fu*k me, I guess. Just can't stand being bested by this damn camera. Okay, I'm done. Rant over...... Thanks again for all replies and helpful comments. Best of luck to you all.
  • @Dalefpf

    You are so strange.
    GH2 runs internal screen at 60Hz as I can understand.
    And it also do not output proper 24p via HDMI.
  • @Dalefpf

    I can see it clearly as well. When recording in 24H the LCD looks like it's updating at about 12-16 fps. When I first got the camera I thought I was looking at the old silent film rate of 16 fps. I'm suspicious that Panasonic is doing some tricks to make the 24h output look more like "cinema with afterimages" as it says in the manual.

    I just did a bunch of tests panning in 24H vs. 1080i, 720p and MJPG modes. The 24h panning is definitely a lot more strobed. This is not just the difference between 30 fps and 24 fps - I've been dealing with that for years. This is something else.

    What's the current status of the "1080 progressive" patch in ptool? is it worth trying this to get a viable high-res alternative to 24H?
  • Are we sure this isn't just post workflow? I too noticed this upon reviewing footage from a recent casting/broll shoot -- great, I thought, I'm going to look like sh*t. But when I actually imported the files into AVID instead of just watching them through HDMI, problems gone. Anyone else had a similar experience -- seems to me once you get in in a NLE that handles 23.98 you're fine.
  • @dalefpf try two things: first find in this topic my suggestion on panning rates and follow it. Do you still see strobing motion in your footage? Do a review on a powerful enough computer (plays fine on a 2009 MBP, also on a 2.66 Quad core duo Windows 7 desktop) If you are on Windows, use WMP, not VLC for a playback. DO not judge based on the viewfinder.
    Secondly, do all of the above but turn off the autofocus or put it into a single mode, rather than c mode.
  • There is something funky about the GH2 that looks more stroby than a GH13..... I don't know what it is either but something is weird.

    I haven't bought a GH2 only played with them... just found out about the hack so now will consider actually getting one or 2 or 3.

  • @JDN

    It could very well be post workflow, I don't know. That would be great, in fact, as it would be fixable. I use FCP7 log&transfer to ProRes422 for most projects. I also use 5DtoRGB to convert footage, though this is still in the testing phase. Should I be considering a different workflow?


    This 24P artifact bugs me but I put it down to small stuff. The posterization/banding and CMOS jello were much bigger issues to my mind. The first seem to be greatly improved by the firmware hack and the second unchanged (and endemic to most DSLRs). Still, I think the GH2 is a fantastic camera. Every camera system includes some kind of tradeoffs. For me, the GH2 is the sweet spot. I'd like to try to dial in the look as much as possible, but I certainly wouldn't stop using it just because of slightly weird motion on pans. In most types of video work, if your audience is thinking about the pans and judder, you have a much bigger problem...
  • Hey guys, I'm on set now and just handed the gh2 off to another cameraman to get his thoughts. Going to let him shoot a bit on break and look at it projected later. I'm convinced it's not a computer problem. My computers are plenty fast but thank you for the suggestions. I'll bouble check what mode it is in. Thanks again.
  • How about this for a test - rig up several cameras to the same tripod head and outfit them with either the same lens or lenses that will give the same equivalent view on a given sensor. So you could have GH1, GH2, 5DmkII, whatever else, and then shoot a series of panning shots. Do it at various speeds, and if you perceive a difference, show us a split screen with the GH2 on one side and the camera you feel has better motion rendition on the other.

    I think the perception of motion is a tough topic for many, only some of us really notice whether the cadence feels right or not. You even hear people saying things like 'most viewers can't tell the difference between 24p and 30p' - well to me it's the most obvious thing in the world. Some people leave motion smoothing interpolation enabled on their 120hz/240hz televisions whereas I find it utterly unwatchable. Even with it turned off, I can see a difference in how my 24" Dell LCD renders 24p versus my 40" Samsung LCD, even bluray at 24hz (and I prefer how it looks on the Dell, unfortunately).

    It wouldn't explain the discrepancies some are seeing in GH2 vs. GH1 motion, but as for digital image acquisition in general, some have theorized it's the difference between electronic and mechanical shutters that accounts for part of what makes film look like film and digital look like digital. You even see this in RED's "magic motion" feature on the Epics; they seem to acknowledge there's more than one way for digital sensors to render motion, and have given people some options. Who knows what the GH2 defaults to?