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Lines in GoPro footage

Discussion in 'General Discussion' started by mindbend, Sep 17, 2013.

  1. mindbend

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    See reference video showing problem:
    [youtube]http://youtu.be/kuhYCuokwjA[/youtube]

    http://youtu.be/kuhYCuokwjA

    Problem:
    GoPro footage sometimes shows "scan lines" (horizontal lines) when used on the Phantom with the Zenmuse gimbal.

    A week after getting the Phantom/gimbal combo I crashed it with the Hero 3 (Black). It was after this that I first noticed the "scan lines". I figured the crash caused the problem, so I eventually got a new Hero 3 (Silver). Sure enough the problem showed on that one too.

    Possible Causes:
    Not sure. Doesn't seem to be the camera, since the problem shows up when using two different Hero 3 cameras (one Black edition, the other Silver).

    The gimbal most certainly was affected by the crash. It seems to generally work in the sense that it stabilizes the GoPro, but just yesterday (a month after the crash) it started this awful screeching. That can't be good. Could a damaged gimbal somehow be causing this issue of showing lines in the GoPro footage?

    What about the electronics inside the Phantom? Could these be affecting the GoPro? If so, how?

    I tried switching out the black carbon rotors for the original white ones that come with the Phantom. This seemed to help quite a bit at first (see clip #3 in my sample footage). But clips 1 & 2 (shot the following day) show the problem.

    The rotors affect the problem but don't seem to be the actual cause (since the problem didn't exist when I initially flew the Phantom).

    It doesn't seem like anything with the helicopter (other than the rotors) is the actual culprit because I have been able to duplicate the problem without having the GoPro connected electronically to the Phantom and without the gimbal turned on.

    Light seems to be a factor. I'm not sure I've had this problem on overcast days. Seems like heavy direct sunlight plays into it. Almost like the Gopro's exposure is being affected by the rotor spinning. BUt then why doesn't everyone have this problem?

    It doesn't appear to be the camera because the problem shows up on at least one other Hero 3.

    Another possible factor is the little spongey things that connect the gimbal to the Phantom. In my crash, I lost three of the four spongey things (the dark black stiff ones). I then used the dark gray ones. Doesn't seem like that would make much difference though.

    Things to do:
    Need to test other variables. The 1440x1080 footage looked good, but will it every time? What about 1440 at different fps? Not sure yet.

    Need to try seeing if I can mount GoPro to gimbal without the back part being plugged in. In other words, can I jury-rig it so the gimbal works, but the GoPro isn't plugged in to the electronics. That way I could narrow down potential culprits.

    ---

    Any ideas? Anyone else experiencing this? Any solutions? Thanks!
     
  2. Netwarrior

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    Yup, Those lines are very common when the sun is in such a position 10:00-11:00 and 1:00-2:00 or that it is causing the prop shadows to break up the sun flare on your GoPro lens at a similar frequency to your GoPro shutter speed. Think of a photo flash or strobe light on a CMOS sensor. Very common on Phantom GoPro footage. Only solutions are to film when the sun is higher or lower or point your lens away from the sun to avoid sun flare. In your second clip you can see barely any shadows. Hence the lines are gone. It's frustrating because the sun position must be in just the perfect height and angle for the lines to appear.


    Sent from my iPhone using Tapatalk - now Free
     
  3. boat chaser

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    +1 netwarrior, I always try and shoot in the morning or afternoon to avoid this from happening.
     
  4. UTR

    UTR

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    Reading the GoPro it has a continuous scan rather than reading a frame at a time it just keeps rolling the scan around which contributes to a lot of the jello at 30 fps without anti vibration mounts etc I get horrible jello but at 60fps I hardly get any. I imagine that if you run at 60fps you will get a different result to 30fps (just watched your vid again and that's what you've done 24 vs 48). Plus you will get shadows at different speeds obviously during manoeuvring. You might try jut angling your camera down a bit. The only other thing I would do is make sure you have your power supply filtered to eliminate any electrical noise from your motors.
     
  5. PTCX

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    You can eliminate those lines by using a ND (Neutral Density) Filter.Grades of .6 and .9 seem to work best.

    If you're using the GoPro in it's waterproof case I recommend the Snake River Prototyping BlurFix SO 3 adapter for use with 55mm filters.
    SRP also does a Micro 52 adapter that fits the naked GoPro HERO 3 but it is too heavy for use on gimbals.
    Some gimbals may be able to be tuned to handle the extra weight but I have not got that far into the gimbal tuning yet.

    I am using a press on adapter with a glass ND filter from Polar Pro that is light enough but is not as high quality as I would like.The filter is built into it,so it can not be changed for a different grade of filter.Also it has slots cut into the back of it that lets light in and that causes reflections on the back of the filter and looks terrible.Those slots can be covered with an 'O' ring to solve the problem.
     
  6. martcerv

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    The ND filters do really help to reduce this, though with the gimbal you are limited especially the DJI one as they recommend not to add any extra weight to it.

    I use the SRP filters but am not getting the DJI gimbal because of them being too weak to hold any filter adapters, not only is it good for this and also giving smoother motion plus reduce jello. They also help to protect the lens in case of a crash, I have recently tried out the polar pro filters and as PTCX says the quality isnt that great. They do tend to wash out the image much more then the better filters I use with the SRP adapter but also have a tendancy to get a real bad reflection when its very sunny and they are needed most.

    Here is an example of some flying with and without a filter on 2 consecutive flights this has been graded but shows full flights. You can see the effect of the ND filter on the props here quite well, the lines in the video are simply shadows off the props and these are distorted with the rolling shutter sensor at high shutter speeds. With the filter you will see how it blurs the props and they are almost invisible, this does the same to the lines in the video. They are no longer as visible due to this blurring but at very high shutter speeds that a gopro gets in good light it pretty much ruins the image.

    [youtube]http://www.youtube.com/watch?v=E34obz9qcTw[/youtube]

    Here is another showing with and without a filter side by side but here my mount had some issues so I will redo these tests next time the sun is out. This video is protune cam raw ungraded just to show the effect of the filters with no incamera adjustment or grading myself in post. Both these next 2 videos have a bit of jello as my 2 camera mount was not great at this point and I have got it much better since and so will do some better filter comparisons on the next nice day, it was also very windy on these flights.

    [youtube]http://www.youtube.com/watch?v=mMZ-UvIEEto[/youtube]

    Here is a video showing the Tiffen filter in the SRP adapter and the Polar Pro filter. Both were clean and the polar pro was actually just taken out of its packaging prior to this flight, you can see the big quality difference between these.

    [youtube]http://www.youtube.com/watch?v=XlfLsvuN86A[/youtube]

    The Polar pro reflection was there on all my flights with both their ND4 and ND3 filters when its sunny. When the sun wasnt out on other tests there is no issue with the reflection but the main point of the filters is to use them when its bright and sunny and so far all my polar pro tests have been pretty poor in such conditions. They do have the advantage of being smaller and lighter but the other issues hurt them so much I wouldnt use them outside of these tests. I also dont think they would do much to protect a lens in a crash, it would be better then nothing but not by much. DJI do say that you should not add anything to their gimbals and so it may also be a better option to get a gimbal that can handle more load then the DJI and its the only reason I havent bought one yet.
     
  7. RedFishChaser

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    Great topic as I have not ventured into shooting GoPro footage yet. I want to shoot with my Sony Action Cam AS15 instead of my GoPro1. I don't want to get the GoPro3 as the Sony produces better images. They use Carl Zeiss lenses! Top of the line lenses besides Nikon Nikkor's.

    Thanks for all that great info!
     
  8. martcerv

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    The sony is a better camera then the hero1 he also has, but the Hero3 black is easily a better camera and it also uses a Sony sensor though a slightly better one then in the Sony action cam.

    So between those 2 cams he has access to the sony would be the better camera I would think. The lenses on the sony are zeis by name but far from the high end cinema lenses they make and unlikely to be any better then what is in the current hero3 black.
     
  9. Piso Mojado

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    Matrcerv: fascinating videos! By what mechanism does a ND filter eliminate the rotating propeller images?

    Thanks!

    Memo
     
  10. martcerv

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    The ND filter reduces the amount of light coming to the sensor, this then slows the exposure and causes the propellers to become blurred. Its only in very high shutter speeds that you see the propellers clearly and due to the rolling shutter sensor this also causes the strange distortion you see I the props. However the props look on camera so will any shadow that comes from them onto the lens and how it reduces the visibility of such lines in footage when sunny.

    Depending on the light you will want to have different strength ND filters to try and get the best possible control over the shutter speeds.
     
  11. mindbend

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    Thanks for everyone's input and help on this. I believe I've confirmed that it is indeed the rolling shutter effect. I built a hood out of cardboard. So far, so good, but I need to test more in varying lighting conditions. I'm also gong to implement the ND approach somehow.

    Here's to hoping they release a GoPro with global shutter to eliminate this! All my best stuff is ruined because of it. I was even filming a little segment for a feature film and we reviewed the footage only to find it completely useless. It was very embarassing and frustrating. At least I know what the problem is, so that's good.

    Thanks again!
     
  12. edunwody

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    Pretty bummed out I can't use my filters on the Zen. The filters really make a world of difference.

    E


    Sent from my iPhone using Tapatalk
     
  13. Quadro

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    Wow!

    Thanks for posting your test videos. Were you flying two GoPros side by side?

    If only I'd found your Tiffen ND v Polar ND test sooner, I could have saved myself the cost of a pair of Polar Pro NDs (naked and waterproof mounts) from B&H. Perhaps I can return them for credit toward a TIffen ND + adapter setup.

    Not sure a global shutter is possible at the GoPro size, but perhaps someday we'll see an adjustable ISO setting with a minimum speed of ISO 25.
     
  14. mindbend

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    For anyone who cares, the cardboard hood I built works great. I've been using it for months now. Also, the Hero3+ is much better at dealing with exposure than the regular 3. For me, the regular 3 would increase/decrease exposure on the fly when I didn't want it to. You'd see random exposure adjustments that ruined shots. The 3+ so far seems to settle in on an exposure and keep it until it really needs to adjust.
     
  15. OI Photography

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    Interesting, thanks for sharing that. Does that seem to happen even in steady lighting?
     
  16. Phantom Lover

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    The lines are from the props giving shadows to the gopro lens. Try a lens hood. samys camera carries it. a ND filter with help slow down the shutter and help with jello effect but the hood is the solution. http://www.samys.com/p/All-Products/OCD ... 48164.html
    hope this helped. it solved my problem. I don't use a filter but i can try that to see if it helps as well with it. Let me know on the findings.