Shooting from a train. iPhone starts to roll?

Discussion in 'Movi Technical' started by John Chu, Jun 13, 2018.

  1. John Chu

    John Chu Active Member

    Joined:
    May 12, 2018
    Messages:
    106
    Likes Received:
    47
    Well, unfortunately, the freeze mode doesn't help. :(

    It still does the same thing:


    I will try to lightly grab the phone the next time I try this with the Movi.
     
  2. Steve Huether

    Steve Huether Member

    Joined:
    May 17, 2018
    Messages:
    96
    Likes Received:
    53
    I noticed the same with it mounted to my truck windshield last night in Movilapse mode... seems its a larger issue of how acceleration affects electronic gyro sensors I guess.
     
    John Chu likes this.
  3. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    I think that if one wants this shot leaving or arriving at a station, the solution is to put the phone on a monopod or shoot handheld. There is a tube steel barrier where the seats meet subway car doors (visible in the first post in this thread and at the beginning of the video two posts up). If desired, this could be used to brace oneself during acceleration/deceleration. I think that it would also be pretty easy to use a suction cup to stick the phone to the subway car wall or one of the windows (although I think I’d want to be in a pretty uncrowded car before doing this, and I don’t know whether the car’s vibration would be a problem).
     
    #23 Rorick Edge, Jun 15, 2018
    Last edited: Jun 15, 2018
    John Chu likes this.
  4. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    I’m hoping to test this tomorrow or Sunday. I’m going to use a 6S (no stabilisation) and a 7 (optical stabilisation) and shoot on a monopod, handheld and with a Movi. Might even bring along a suction cup mount. I’m going to do the test on the 7 line. Much of it is above ground and I want to see, in daylight, how the iPhone’s rolling shutter affects the footage.
     
    #24 Rorick Edge, Jun 15, 2018
    Last edited: Jun 15, 2018
  5. Steve Huether

    Steve Huether Member

    Joined:
    May 17, 2018
    Messages:
    96
    Likes Received:
    53
    Sometimes the low tech solution is the most reliable.
     
  6. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    Yes. With a GoPro or a Sony RX0, I would do this shot with a mouth mount. The head is a great natural stabiliser. Pity that mobile phones are such an awkward shape :)
     
  7. Steve Huether

    Steve Huether Member

    Joined:
    May 17, 2018
    Messages:
    96
    Likes Received:
    53
    I've seen a few mouth mounts hacked together for smartphones... definitely look interesting lol
     
  8. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    I’ll do a search. I think I’ll bring along my RX0 to do a comparison. For the mount, I use a GoPro Quick Clip and a GoPro mount to 1/4” 20 adapter. It works really well. The parkour/free running and surfing crowds have some pretty inventive ideas, mouth mounts being one of them.
     
  9. Steve Huether

    Steve Huether Member

    Joined:
    May 17, 2018
    Messages:
    96
    Likes Received:
    53
    Yea there some pretty good ideas out there. Mic Bergsma has a ton of GoPro oriented tips too
     
  10. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    Ha! Turns out there are several YouTube videos on how to make a mobile phone mouth mount out of a sheet of construction paper and tape. It might actually work, at least for a brief subway shot:

     
    #30 Rorick Edge, Jun 15, 2018
    Last edited: Jun 15, 2018
  11. Rorick Edge

    Rorick Edge Active Member

    Joined:
    May 11, 2018
    Messages:
    452
    Likes Received:
    81
    I’m now convinced that the mouth mount described in the video in the previous post will work. The same guy made a video that shows his younger brother using it. See the 06:12 mark to 14:32 below. Given how active the kid is (his older brother, who is filming, is into free running), it’s quite a bit more robust than I would have expected. It costs pennies to make; definitely worth experimenting with.

     
    #31 Rorick Edge, Jun 15, 2018
    Last edited: Jun 15, 2018
  12. John Chu

    John Chu Active Member

    Joined:
    May 12, 2018
    Messages:
    106
    Likes Received:
    47
    See Reason #8

    https://freeflysystems.com/movi-m5

    It can affect the professional versions too.. but the GPS feature can mitigate it.

    Hey..my iPhone has a GPS. ;)

    (But wouldn’t work underground anyway.)

    Anyway.. just needed the sanity check. Moving on. Rare use case scenario.
     
    #32 John Chu, Jun 16, 2018
    Last edited: Jun 16, 2018
  13. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,372
    Likes Received:
    1,162
    Correct : gravity and horizontal acceleration are the inseparable in that
    You are correct John -- you cannot easily get around the fact that accelerations, be they from gravity or other acceleration, are sensed as identical forces by the accelerometers and gyros. GPS can be used to assist in detecting the direction of horizontal motion and the rate of change of that can be used to infer acceleration, but I don't think GPS is really accurate enough (or can be detected changing fast enough) to null out the effects your Movi is experiencing.

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
    John Chu likes this.
  14. John Chu

    John Chu Active Member

    Joined:
    May 12, 2018
    Messages:
    106
    Likes Received:
    47
    Even though I said I was "moving on".... Here is my "solution" to the problem of the horizon rolling while shooting in the train:
    Unlock the roll, then “steer” the Movi slowly like you are driving a car to keep it level. (easier said then done though) So I just add a bit of counter steer if the phone starts to tilt and roll. It works ok during acceleration and deceleration. The operator is the A.I. for the Movi in this case. Touching the phone was a bad idea. (I tried it).
     
    #34 John Chu, Jun 17, 2018
    Last edited: Jun 17, 2018
  15. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,372
    Likes Received:
    1,162
    Definitely worth trying your approach, John. I suspect it will take a deft hand to get it just right but, with a bit of practice, it should work!

    Andy

    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     

Share This Page