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How I Fought Jello With Gel + HERO4 - And Won

Discussion in 'Phantom 2 Discussion' started by herein2014, Dec 30, 2014.

  1. herein2014

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    Background

    I have been fighting with a persistent jello problem for about 2 weeks now. In case you are not familiar with it, jello is the wavy appearance that shows up in video when a camera with a rolling shutter and a CMOS sensor is subjected to high or low frequency vibrations as it is filming. My jello problem was very intermittent and barely detectable but I'm a bit of a perfectionist so I refused to settle for anything less than jello free video.

    I have a DJI Phantom 2 with the H3-3D gimbal and started out with a GOPRO HERO 3+ Black edition.

    Things I Tried That Did Not Work

    Gain Settings - Plenty of discussions around jello referenced gain settings so I tried various gain settings. None improved the situation and most had some other undesirable side effect (i.e. not flying straight, drifting at hover, slowly dropping, etc). In the end I went back into the DJI Assistant software and selected Default.

    Different Bushings - The H3-3D shipped with 4 sets of bushings, with the recommended bushings being the white ones and the rest being different levels of firmness vs. the white ones. I tried the harder ones and it made it worse, I tried the softer ones and the whole gimbal shook so bad it was hitting the underside of the Phantom. So in the end I went back to the white bushings.

    Prop Balancing - I tested the balance on all of my props and they were all already balanced. Just to be sure I went through 4 sets of props to see if it made a difference, my conclusion was that it was not the props.

    Motor Balancing - I took the props off and ran the motors at full speed without the props attached. The Phantom was rock solid no vibration whatsoever so I concluded the motors were properly balanced.

    Flying Slower - Some users have reported they only get jello at higher speeds so I tried flying slower. Certain maneuvers still resulted in jello no matter how slow I flew.

    Things I Tried That Helped

    Gel Insoles - I saw in a YouTube video that some users had had success with putting dampening material between the H3-3D gimbal and the Phantom's underbody. So I tried a few different types of materials and found the one that helped the most was a gel insole. I cut the insole to the shape of the H3-3D mount and cut out a hole for the middle of the insole for the gimbal to fit through then used slightly longer 3mm screws to screw the gimbal back on. Afterwards you will need to do an advanced IMU calibration so that the gimbal can compensate for the new addition.

    Make sure you check the clearance between the bottom of the gimbal and the ground after adding any material like this. I started out with an insole that was too thick and the gimbal hit the ground on landing because it was slightly lower than the landing skids.

    60FPS Frame Rate - The gel insoles eliminated about 95% of my jello but there was still a tiny bit remaining that would show up occasionally. I was able to eliminate 99% of my jello by increasing the framerate on my GOPRO HERO3 Black camera to 1080@60FPS. The problem with this is that I always take a picture every 5 seconds while recording so that I don't have to fly twice...once for video then a second time for pictures. The problem is the GOPRO HERO3 Black will only take pictures and record video simultaneously at 30FPS - which is where I was encountering the jello.

    GOPRO HERO4 Black - I was FINALLY able to eliminate 100% of my jello with this camera. I noticed in the HERO4's specs that it would shoot 720P@60FPS and take a picture every 5 seconds; something the HERO3 Black could not do. So I got the camera thinking I would settle for 720P as long as @60FPS I would have jello free video and a picture every 5 seconds.

    As a baseline I decided to take the HERO4 up in the Phantom and shoot at 1080P@30FPS + Picture every 5 seconds just to make sure the jello was the same before moving to 720@60FPS. Much to my surprise even though it was shooting at the same frame rate as the HERO3, the video was 100% jello free. The only thing I can figure is that since the processing speed of the HERO4 is 2x the speed of the HERO3 maybe the rolling shutter processes the image 2x as fast as the HERO3 - effectively halving the CMOS exposure time without actually increasing the frame rate.

    Wrap-Up

    If you have unbalanced props or motors I do not think gel or the HERO4 will fix your jello, but if you have eliminated every other source of vibration and have reduced it to the least amount of jello possible, then you may want to try the HERO4 if you are still not satisfied. I'm not certain I still need the gel insole between the gimbal and the Phantom, but my setup right now is so perfect I don't want to risk changing anything.
     
  2. Buckaye

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    Shoot.... Looks like I'll be getting a gopro 4 when I scrape up the extra dough :) lol
     
  3. knuckles

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    Did you ever try a lens filter? I thought a ND filter is supposed to help eliminate jello as it does something to shutter speed I thought. I'm sure I saw something like that in a video review on polar pro filters.
    http://polarprofilters.com/shop/frame-n ... opro-hero3

    I have that ND filter but I'm using a CP filter instead at the moment
     
  4. herein2014

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    I have that filter but I did not use it to try to eliminate jello. I did not consider using a lens filter a viable option. It comes with its own side effects such as having to counterbalance the gimbal, and it can be easily damaged during landing. I use the ND filter for certain effects, but putting it on for every flight and hoping it would eliminate jello was not a good enough solution in my opinion.

    Also I use this lens hood for cloudless days: http://www.samys.com/p/Action-Camera-Ac ... 48164.html and it completely eliminates prop shadow without changing the other characteristics of the video so I would not have been able to use the lens hood if I had to rely on a ND filter.
     
  5. hemorrhagic flyer

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    There in no "hoping" involved. An ND filter will eliminate jello because it forces the GoPro to use a slower shutter speed.

    This has been well-documented for a long time.
     
  6. herein2014

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    An ND filter does not always eliminate jello. The frequency of the vibration, the ND filter rating, and the amount of sunlight on that given day will all determine how effective the ND filter is. All an ND filter does is reduces the amount of light that reaches the CMOS. When the reduced amount of light is detected, the GoPro reacts by slowing down the rolling shutter to compensate for the decrease in light...if the amount by which the shutter has been slowed allows for the vibration to pass before the CMOS commits the image to memory then the jello will be eliminated; if the day is particularly bright or the vibration's frequency causes it to intersect with the new shutter speed...jello will still occur.

    This too has been well documented. There are plenty of reports of mixed success with just trying an ND filter, which is why I chose not to "hope" an ND filter would fix my issue. I haven't even mentioned the other side effects such as the impact of an ND filter in a low light scenario. If you are flying like I am strictly to get the best quality footage possible, then you only use an ND filter when it will improve the footage; not to hide problems with your setup.
     
  7. Buckaye

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    Great info herein2014! I learned a lot from this post.

    Thanks!
     
  8. ianwood

    ianwood Taco Wrangler
    Staff Member

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    Good write up. I agree that an ND is not the fix for vibration. It will hide the jello by slowing the shutter down but your image will also be less sharp. Curious to hear more about the gel insert. Can you link to the video? Maybe some pics of how you did it.

    I've been struggling with vibration in the cold. I've added foam earplugs into the vibration dampeners as some have suggested and that seems to have helped quite a bit. Looking for the last 15%.
     
  9. FpvDee

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    Thanks for the gel tip. I might try that… I get a little Jelly with my Hero3+ black when moving fast in bright sunlight.

    Just a heads up… Not al ND filters are created equal. the polar pro ones are terrible. Softens the image poorly. I've been using the snake river ND+CP filter and the glass is excellent!
     
  10. FpvDee

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    What was the brand model? you used? also how hard did you torque down the 3mm screws underneath? I'm thinking firm/snug would do it, but too tight it won't work.

    Also I don't think you'd need to re-calibrate the gimbal if your just adding gel between the mount and phantom, unless the angle gets off somehow, but if you torque evenly it should be level.
     
  11. Khudson7

    Khudson7 Guest

    Great info...about the gel and GP4...THANKS!
     
  12. herein2014

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    I torqued until they were just tight enough to start compressing the gel. I think the amount of torque needed would vary for each Phantom because the frequency of the vibration will be different for each one. You could try different amounts of torque but at that point you are pretty much turning the gel into a compression damper and it would take a lot of trial and error to find the perfect torque for each screw. Plus the slightest change and you have to start the whole process back over.

    All I did was add the gel, tighten the screws and did an advanced calibration. Anytime I remove the gimbal for any reason I always do another advanced calibration after reinstalling.

    Attached are pictures of the underside of my Phantom.I also included a picture of the nylon screws that I used to replace the original plastic pins. The screws are reusable vs. the pins.

    Here is a link to the gel: http://www.walgreens.com/store/c/walgre ... 04-product

    Here is a link to the screws: http://www.lowes.com/pd_139028-37672-88 ... facetInfo=

    Here is a link to the cap nuts: http://www.lowes.com/pd_139007-37672-88 ... facetInfo=
     

    Attached Files:

  13. FpvDee

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    Thank you so much for the detailed write-up. Those plastic clips really do suck. I might just use a zip-tie instead loosely looped.
     
  14. mendezl

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    hey herein2014

    What is that QR Code... your contact info? Good idea!
     
  15. jcknows0

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    I waited to make the GoPro jump as I knew the new model would be 4k and this is ideal for aerial video. This camera has the most amazing processing power I have seen in a form factor this size and once uncompressed and encoded to 10-bit, the video is unreal. That being said, I am deeply concerned about heat issues which will only be exacerbated in summer heat I made sure to get product protection on it as my first one died after less than a month strapped to a micro quad (BB was cool about it hence why I got protection for this one).
     
  16. herein2014

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    No idea, it came with it, probably goes to DJI's website. If I were to put my contact info I'd rather just put a phone number and email, few people ever seem to actually bother scanning QR codes.

    Well I have taken apart my GoPro HERO4 already and it does have a heat sink that the HERO3 did not have. In this video @ 2:40 he discusses the heat sink: https://www.youtube.com/watch?v=JyebWw7K_5Y so I assume GoPro even fixed that problem in the new version. I didn't bother with product protection, taking it apart to install my custom lens voided the warranty.
     
  17. cokeaddict

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    I have used 3 polar filters and none of them have any affect on quality footage.
    Gello is a thing of the past for me ever since I started using the filters. Personally I think you much have encountered a faulty filter.
     
  18. TuT

    TuT

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    The Hero 4 is also approx 10g heavier than Hero 3. This would affect vibrations with more inertia.
     
  19. mlsantos28

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  20. wkf94025

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    Nice post Herein2014. I will take the gel for a ride and see. Did I miss something on the nylon bolt and nut? Are those in place of zip ties and DJI retention pins? If so, on all 4 corners, or just front two, or ?

    Kelly