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GH2 in 24p: noticeable "strobe effect" with any motion in frame?
  • mo7iesmo7ies

    Clearly, ANY camera that only samples time at 24fps will have visible motion artifacts.

    However, I find these to be more pronounced on the hacked GH2 than on any other 24p cam I used. Am I seeing things, or is it a reality?

    Not only in my own video tests, but also when I watch other folks' videos, everything looks Saving Private Ryan / Battle Royale to me.

    As if shutter speed was super high. Except it actually wasn't set that way! In my tests, I keep 180 deg shutter (about) with 1/50 at 24p. So then, why do we get that strobing, high-shutter-speed-like look?

  • 259 Replies sorted by
  • StillStill

    It's very simple. Try taking a photo of a falling object with a flash in strobe mode. The same effect. At settings of 25 fps, 1/50, double exposure occurs, as the frame is exposed twice. So we see a double contour. Either lower the shutter or on the post use RSMB plugin or something similar.

  • goannagoanna

    @falconking

    Thanks for contributing one of the few videos along with settings for that judder look we all know and love ;-)

  • falconkingfalconking

    I have tried many settings and hacks, but the strobing/judder refuses to go away. Even without the hacks, the result is the same. settings: 24h , 1/30th ISO 1250, cinema mode. take a look:

  • sicovdplassicovdplas

    I have strobing/judder on the bmc, it's WAY more visible then on the gh2, i'm not sure whats going on but 24p handheld is nearly impossile due to strobing accuring.

  • vicharrisvicharris

    I'll PM you the PSA on Vimeo so you can see what it all looks like. It's still a working edit. :)

  • matt_gh2matt_gh2

    Very cool - will definitely be running my tests with 1/30 - great suggestion.

  • vicharrisvicharris

    @matt_gh2 So far the only place it's come back to bite me on the ass is on a car shot I did. I had the camera on the front of the hood looking back with the SLR Magic 12mm and got some pretty bad rolling shutter. I knew it might happen but I needed the extra stops shooting with only street lighting at night. Looking back I should have shot it at 720p 60 and jacked up the ISO and clean it up in post. Learning lesson I guess. I don't mind the motion blur. The look of 1/50th shutter is ridiculous to me. Maybe 1/40th but I love the 30. On that PSA I was working on we did a scene with a guy running buy camera after a bus and I panned with him, tracking him. Looked fine to me. Looked like it does in the movies. Yeah there's motion blur and alot of it but that's what it looks like. Thanks for the test grade btw! Forgot to tell ya that.

  • matt_gh2matt_gh2

    @vicharris Very interesting re 1/30 vs 1/50. Will have to test myself. Are you getting good results for shots where 1) subject is moving and camera is on tripod 2) where cam is moving and subject is stationary, and 3) where both subject and camers are moving? In other words, any situations that give you trouble when using 1/30. Thanks

  • vicharrisvicharris

    @thankyou Shoot it at 1/30. I shoot everything at that now and it looks great. The blur looks like film. 1/50th kills me now. Just try and see. I have no idea why people are set on shooting at 1/50th here.

  • WodenDigitalWodenDigital

    Just watched this Vimeo test.

    Looks about right to me; taking into account speed of motion through frame, for a 50mm lens and guessing distance from subject.

    I am about to do a shoot with the GH2 so will see if I find any validity to this GH2 issue. I've had issues with RED when I first started using it as there is a hard line and a high resolution. It's not as forgiving and organic as film.

    Canon's and other softer acquisition devices will naturally even out this kind of issue, because the codecs are a bit of a mess.

    I'll know more after I shoot.

  • thankyouthankyou

    Hello, thank you everyone who has contributed to this topic. Could you please watch the example video:

    test from INHUMAN on Vimeo.

    (the password is personalview)

    and say that it is the same thing. This stutter kills me! (look at around 7th second of the clip). I used Cinema mode, 24p, 1/50 second, everything -2, (noise reduction 0), smooth, Flow motion v 2.02 patch, the lens was Nokton 25mm, 0.95.

    So what is the final conclusion on how to minimize this. Is it to set the shutter to 1/30 or to use HBR mode and 29fps.

  • thankyouthankyou

    .

  • goannagoanna

    @Jim_Simon Thanks for replying. I'm glad somebody has noticed. This put a lid on the mystery.

    (Quiet popping of champagne corks)

  • goannagoanna

    @Jim_Simon

    These results show that motion artifacts are determined by sampling rates and the rate at which the image sequence is up- sampled during reconstruction. A very simple and easily implemented filter mitigates this annoying visual artifact. Because high-resolution displays require severe data rates, finding the sweet spot for sampling and reconstruction will have important consequences for electronic displays and image communications systems.

    The paper certainly doesn't mention a filter in the way we're used to; perhaps they are referring to filtering more like an algorithm which might determine the up-sampling of a given piece of video. In any case, the paper's terms of reference do not include the actual building and deployment of the judder remedy they allude to.

  • Jim_SimonJim_Simon

    Well...what filter?

  • goannagoanna

    Motion artifacts are determined by sampling rates and the rate at which the image sequence is up-sampled during reconstruction. A very simple and easily implemented filter mitigates this annoying visual artifact

    Objects in nature tend to move in smooth trajectories. When motion is sampled by a video camera and reconstructed on a display that natural smooth motion can appear to be jerky and irregular.

    ....

    The moving object in world coordinates jumps across the frame of reference in discrete static steps. During the reconstruction the eye is smoothly pursuing the motion across the frame of reference. The pursuit eye movements match the average velocity of the moving object in nature. The reconstructed object, however, only moves relative to the scene at the sampling rate, i.e., when the image changes.

    from Judder-Induced Edge Flicker at Zero Spatial Contrast
    by James Larimer, Christine Feng, Jennifer Gille, Victor Cheung. Article first published online: 5 JUL 2012

    Download PDF -286KB

  • GH2avidGH2avid

    Hi guys, I'm about to shoot with the GH2 using a jib. I'm planning to use Driftwood's Sedna AQ1 with Sandisk 64GB 95MB/s. I've read somewhere on these threads that shooting VMM 80% helps a lot with the judder issue when the camera pans. I'm trying to test this out but haven't noticed any improvements yet. I'm wondering if my post production workflow is wrong?

    I'm transferring the MTS files onto my macbook pro HD and converting the files with 5DtoRGB batch. 5DtoRGB reads the VVM 80% files as being 23.976 so following on from LPowell's note that the files are actually recorded at 29.97 fps (and don't need to be sped up in an NLE) I'm telling 5DtoRGB to encode them at 29.97. Is this the right workflow?

    Or should I import them into AE and interpret the frames as 29.97? If so, how do I export the MTS files from AE so that I can then transcode them with 5DtoRGB?

  • driftwooddriftwood

    Wait for Canis Majoris Day AM...

  • MisterJMisterJ

    @driftwood Yes, but what You think about Cluster 6 compared lets say Sedna AQ1 in 24H mode? I think that Cluster has les strobing effect and still, it does not have any of that bothering 'tweening' problem. I've been testing these two hacks side by side last two days and think that Cluster 6 has advantages in motion = bit faster pans and tilts before strobing is visually there.

  • RobertoRoberto

    In AVCHD there is no user control with these 'tweening' prediction frames

    If there really is just one nutshell we could put this stuttering 24p problem in, I like this one the best.

  • AstroAstro

    @driftwood Yep agreed...I like the feel of all Intra best for 24P, so thats mainly what I shoot with, I just pan and adjust the shutter accordingly. As I mentioned earlier ..if there is a lot of motion and movement and it looks too juddery on 24P, then 29.97 works for me, other than that I really love the image quality of 24P.

    As far as 24P goes I shot some footage the other day for a music vid and it was hard to believe that type of quality can come from such a small and relatively cheap camera....just amazing and holds up very well in post.

    A question (even tho I have done many tests) is there really much difference between the contained bitrate All Intra settings (such as Quantam 100) and the higher bitrate ones (such as Crossfire etc...)?

    Plus strangely enough some of the longer GOP (cluster etc..) settings seem to produce a better image in HBR. (Although I have some more tests to do on that) Do you have any all Intra settings that you would recommend as being great in HBR as well?

  • driftwooddriftwood

    @bannedindv Exactly. Motion will always look better in Intra - my Intra settings are set pretty high to keep the IQ up too. Yes its costly in bitrate, but what do you want? Shit?

    Optical distortion has been with us since the very first day a photographer shot movement. With the GH2 we are without all the neccesary shutter speeds to perhaps compensate motion unlike higher end cameras but Intra will render the best possible motion. Period. 'Tweened' is in my opinion the wrong analogy being used for predictive frames and motion vectors - this is an animator's term of working in pairs of frames. In AVCHD there is no user control with these 'tweening' prediction frames - we are reliant on prediction of the h264 alogorithms. Tweening in animation is eventually rendered to full frame. On the contrary, i frame only is constant full frames - it records what it sees. Just try and get your shutter speeds and panning adapted to the frame rate. That's all.

  • bannedindvbannedindv

    No one here seems to be thinking about GOP1 - shoot intraframe, it looks so so so much better for motion.

  • MisterJMisterJ

    Thanks for the info and great tips @LPowell and @Astro!

    That is exactly so as Astro mentioned. Intra-hacks are great in detail and detail can take you a long way. Myself I shoot a lot of static shots and there detail is the key feature. But it's good to have different kinds of approaches what hack is trying to do. And there I think LPowell has done a great task.

    And @Driftwood too. Speaking of witch I've done some testing with Driftwood's latest Cluster 6 and it's really promising. Best thing in that hack is that you get really great quality 2k mjpeg so it is easy to jump from 24H to mjpeg 30fps when you are shooting handheld(I always use shoulder rig). With that setting I can shoot in situation where I need to pan from person to another and so on. And that 24H looks just great with modest datarate. Great setting for documentary filmmaker or such. As Flowmotion is too.

    Well monitoring material is tricky thing. I'm on my summer vacation and don't have the best monitoring with best videocards at the moment. So I've looked material via my home-edit and then used my Home tv-screen witch has 24p -support. In home-edit I have only 60hz monitors, but tv-screen gets it quite close.

    Cheers, misterj

  • AstroAstro

    Wow...The thread came back to life....LOL!!

    I am one of the ones that had complained earlier on this thread about excessive strobing (even using the latest hacks) I will be happy to post some of my earlier clips showing small sections of the original MTS files for anyone who says they have never seen this...or its totally normal, or curiously that no one ever posts any examples etc...

    For me tho I have noticed it mainly panning the camera when there is higher contrast...black letters on a white or yellow background, trees against a blue sky...that kind of thing.

    Anyway for me the Driftwood all Intra or Flowmotion 2 hacks produce such a beautiful image that I am very happy with, so I just use workarounds for 24P...(shoot on overcast days, dont pan fast....or not at all) keep human motion so its not too extreme) etc..

    I really think if you plan to pan the camera a lot or are shooting sports its probably better to use 30P frame rate...as the problem is not really there, I have done countless tests on this BTW...at all relevant shutter speeds in 24P, and using several hacks as well. Also as LPowell pointed out 30P probably has a more fluid feeling on 60hz monitors, so its less troublesome overall and thats a fact.

    Bad juddering with the camera in 24P almost looks like the object is jumping back and forth slightly as the camera pans past (even quite slowly), its easy to see and very easy in higher contrast footage.

    But for me...I have more or less put it to rest, I know what the weaknesses are with 24P and I just work around them. I have never used a Red, but I have studied a lot of Blu Rays that were shot at 24P on the Red...and yes it is there too, but I would say its definitely less. As I mentioned earlier I saw it on Ghost Rider spirit of vengeance when the camera was panned over hi contrast rocks (similar to the GH2, but not quite as bad)....at 1hour 6mins....and other films too.

    Personally tho...I have ended up using the all I frame hacks for 24P, mainly cause I love the detail and Flowmotion for more movement on 24P...and 30P for everything else. You just handle the camera very very carefully in 24P (use shoulder rig) and so on. Cheers

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