Super bumpy in the wind: OK?

Discussion in 'Cinestar 8' started by Steve Maller, Jan 21, 2013.

  1. Dan Coplan

    Dan Coplan Member

    Joined:
    Aug 8, 2012
    Messages:
    83
    Likes Received:
    1
    I have followed all the procedures for balancing the camera - pretty darn tricky especially with a camera as small and light as the T2i, but got it very close. I noticed after I did this flight that one of the forward facing gimbal shafts was higher than the other causing a slight twisting of the horizontal camera plate shaft and hence Dutch roll. But as far as balance is concerned, it should be pretty good. And I was very careful when installing the Radians and all three are near horizontal if not dead on.

    Steve - why would the optical center of the lens need to be center to the axis of the roll? I understand if you're actually doing shots that roll, but if the camera is meant to remain level, it doesn't seem to me like this would matter. And aligning the optical center with the axis could prevent side to side balance unless counter-weighted.

    I'll put the gains back up but that still doesn't account for the jumpiness and twitchiness I'm experiencing. That's what I'm finding very frustrating and need to resolve. Possibly defective or very unlikely?

    As for balancing, I find the whole system very crude, slow, and hard to dial in precisely. I would LOVE a lightweight plate with screws you could turn for at least two axes to fine-tune the position of the camera. Like on my Steadicam. Even though it adds weight, I did add a quick release plate which both allows for quick release of the camera (a godsend) and at least the ability to slide the camera back and forth in small increments. Or I could mount it horizontally for side to side adjustment. And it raises the camera a bit to help zero in the CoG for this particular camera.

    Any thoughts on why the Bootloader software isn't 'connecting to target'? I don't think this is the problem but it could be and I should be able to connect without issue.

    Thanks for all your feedback!

    Dan
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    Think about it...if the Radian on the roll axis is attempting to stabilize roll behavior and the lens isn't in the center of the axis, the video will end up "rocking", as opposed to rolling smoothly.

    And if your camera's CoG is not at the center of the lens (and few are), then move both the camera mount plate and the roll bar to one side or the other so that the entire gimbal compensates for the camera's CoG. Sounds complicated, and it is. I have trouble doing it myself, but once you get it right, it's not so hard to repeat it (when you change cameras).
     
  3. Dan Coplan

    Dan Coplan Member

    Joined:
    Aug 8, 2012
    Messages:
    83
    Likes Received:
    1
    Steve - interesting. In theory the Radians should compensate for roll and all being ideal, aligning the optical center with the axis shouldn't matter as the camera would always be dead nuts horizontal, but you bring up a good point and "ideal" is often as reliable as weather forecasters. Good point! Will add that to my list of stabilizing steps. Unfortunately, that still doesn't help me with my jumpy and twitchy gimbal...

    Dan
     
  4. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
    I have thought quite a lot about it, and to my logic the lens does not need to be centered. Picture what the roll radian is doing, or just watch what it does. It keeps the transverse gimbal bars level with the horizon. All the "rocking" happens above the roll pivot point. Whether the lens is centered or off-centered a bit should not matter. But for sure the left/right COG of your mass matters so that the servo's workload is balanced.
    As far as balancing the camera on the roll axis while maintaining a perfectly centered lens with a combo of camera plate and roll bar adjustment - I have not been able to do this with any of my cameras. Spent hours trying...So I've accepted an off-centered lens to achieve my balance point.
     
  5. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    One possible way to get the balance and keep the lens horizontally centered is to put weight in the tilt arm booms. Someone mentioned this on the forum in a post that they put lead in one of the booms. Of course that just adds additional weight but is an interesting approach.
     
  6. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    I'm no engineer, but I believe in theory, the best way to actually balance a camera would be to mate its CoG with the CoG of the copter itself. My assumption is that the copter's likely to rotate around its CoG, not that of the gimbal. And unless the copter's in perfectly level flight, some of the copter's movements (such as ascending/descending) won't be able to be stabilized. Maybe we're fighting a losing battle, but I think not, as there's plenty of buttery smooth video out there.

    Maybe I’ll just abduct Jeff or Tabb and make them show me their magic voodoo balancing secrets. :mad:
     
  7. Josh Lambeth

    Josh Lambeth Well-Known Member

    Joined:
    Jun 29, 2012
    Messages:
    1,313
    Likes Received:
    214
    Steve if you do this please let me know what I can do to help in that process. ;)
     
  8. kjetil tønnesen

    Joined:
    Aug 16, 2012
    Messages:
    417
    Likes Received:
    23
    if you lift the cameraplate up about 1,5cm then you get the spot
    mine cs gimble with sony 730 is perfekt balanced on roll and tilt

    it stays still wherevery i put the camera with belts off
     
    Steve Maller likes this.
  9. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18

    I think we all agree there, about finding camera COG. It's just that COG does not necessarily coincide with the center of the lens.


    on another thread by Tabb: "It is not a huge deal if the lens is not perfectly centered on the roll axis. It would be ideal that way but in practice most of my ships it does not line up perfectly either." -Tabb
     
  10. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    The Oracle Hath Spoken. Thanks. I missed that post.
     
  11. Steve Maller

    Steve Maller UAV Grief Counselor

    Joined:
    Oct 30, 2012
    Messages:
    3,979
    Likes Received:
    807
    I may need more duct tape. And rope. And chocolate.
     
  12. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
    Haha, I need more of something!
    My lady has become an octocopter "widow" for all the time I spend tinkering and reading this forum. It's gotten a bit ridiculous. Someday (hopefully soon) these machines won't be so finicky. I'd rather spend time perfecting my flight techniques than the endless hours, balancing gimbal, props, gain settings, then dynamic motor/prop balancing, gimbal plate modifications, rubber bumper experimentation, etc...etc...Obsessed. I have given up for the time being on flying my 5dMII with any decent results. The cx760 though takes away most of the headaches, at least for me, but other than the BOSS stabilizer it's a terrible camera. And I sure didn't invest in a C8 to be flying around an AVCHD handicam with no manual control.
     
  13. Joe Azzarelli

    Joe Azzarelli Active Member

    Joined:
    Jul 13, 2012
    Messages:
    210
    Likes Received:
    26
    A good idea for a ladies t-shirt: "Cinestar Widow"

    Not to defend the CX760, but it does have some usable manual controls. I much prefer the look of the FS100, but for everyday video the 760 at 60p or 24p is nice.

    Joe
     
    Bryan Harvey likes this.
  14. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
    That WOULD be a good T-shirt - the shadow of the Cinestar looks like a giant spider or black widow anyway! ;0)

    Joe, not being able to lock exposure is a deal breaker for me. Often need to expose for the highlight and let everything else go dark or silhouette, but not possible with the cx760. Or simply panning across a scene with different exposures - not possible without an exposure "search" by the camera. Just waiting for the next iteration of Sony camera with the BOSS stabilizer and manual control!
     
  15. Joe Azzarelli

    Joe Azzarelli Active Member

    Joined:
    Jul 13, 2012
    Messages:
    210
    Likes Received:
    26
    Bryan
    Not sure I completely understand as I am able to manually control exposure using the wheel. Lock down the gain, set zebra to 100 and dial down the exposure. But since I am using the camera almost exclusively on the copter in daylight use, I have not tried to accomplish any special effects with challenging lighting. I just use the manual exposure to keep from blowing out highlights and pull up the rest in post if necessary.

    Good luck!
    Joe
     
  16. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
    Hi Joe,

    Unfortunately the cx760 only allows fixing two of the three parameters for recording an image. Whichever two you set, it defaults the third into auto mode. For example, if you set manual exposure and fix the gain (ISO), then the camera defaults to auto shutter resulting in unpredictable and undesirable auto adjustment of the shutter. I too only use the cx760 on my Cinestar in daylight. Not trying to do any trick photography. But even the most basic of shots require all the parameters to be fixed. Of course it's possible to get usable shots from the cx760, but its limiting for no reason. Too bad. Would have been just as easy for Sony to make the camera able to fix all parameters.
     
  17. Joe Azzarelli

    Joe Azzarelli Active Member

    Joined:
    Jul 13, 2012
    Messages:
    210
    Likes Received:
    26
  18. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,357
    Likes Received:
    1,161
    Joe:
    I've looked through all the materials I could find on-line and I can't see anywhere that describes the exposure modes and/or manual operation.

    What I've not been able to find on-line is the manual. But I did find this:

    On the front left of the camera you'll find a dial that functions as a manual control for focus, exposure, iris, shutter speed, AE shift or white balance adjustments, but only one at a time. The remaining settings run on automatic control. And while experienced shooters can tell you automatic features aren't perfect, their response time is respectable as long as the shooting conditions don't change too fast. Indoor and outdoor shooting returns quality video and stills. The indoor shots are grainier when at 24db gain, but the quality is still very reasonable.​

    So, it looks like Sony still doesn't get the need to be able to set everything manually, if I'm reading the above correctly.

    Andy.
     
  19. Bryan Harvey

    Bryan Harvey Member

    Joined:
    Nov 3, 2012
    Messages:
    227
    Likes Received:
    18
    Andy, as it has XLR audio inputs I'm 99% certain they would provide full manual controls as only semi-pro or pro operators would be using XLR's. now all we need is someone to hack it with a higher bitrate!
     
  20. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,357
    Likes Received:
    1,161
    Guess I'm just going to have to buy one, right?
    All in the name of science.... :)

    Andy.
     

Share This Page