Forum 2018-08-06T22:58:13+02:00
Keyframes position ...
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Keyframes position aren't recalled correctly  


Eminent Member
Joined: 5 years ago
Posts: 30
22/08/2020 6:31 pm  


I'm trying to shoot some video clips where I'd want to have the subject stay in the center of the frame while the slider moves. I'm using a three axis setup I self built using three Nema 17 motors. Motors are calibrated and saved as my default setup.

As you will se from the attached video clip, the subject (in this test the Marshall amp logo on the speaker cabinet, low quality shoot just for test purposes...) doesn't remain the the same position I have saved in the start and end keyframes during the movement.

Also, looks like the three motors aren't moving simultaneously, rather, looks like the slide is the first one, then pan, then tilt.

I'm also still having issues with the slider controls like I told you in another post of mine (they are still behaving awkward when I try to do some small adjustments, it seemed to be fixed but it's still there, either in video and timelapse mode, buttons are OK).

I'm on iPhone XS, iOS 13.6.1, Pine app v 3.1, Pine FW 3.0

Any ideas?



Video: Test video shoot



Black Forest Motion Moderator
Joined: 6 years ago
Posts: 111
22/08/2020 8:03 pm  

At the beginning of the video, it looks like you are manually moving to the keyframes by pressing and holding the keyframe icons. In this case, each motor will always move at its own best appropriate speed. So in this case, the motors will always stop movement at different times. I think I explained it in a previous post already. It is not recommended to do any filming sequences by moving to the keyframes manually. Always use the play button to properly start and stop the filming sequences. 

At the end of the video it appears you operate the video movement in loop mode? 
Are you trying to achieve that the Marshall logo always stays in the center of the image? If so, many things need to be right:

First, the location of the slider in relation to the object of interest (marshall logo) needs to be exactly parallel.
Then the motor ease values will affect the movement. Setting all to 0% will help here but might introduce shacking and vibrations.
Your slider might have backlash, which will affect the final slider positions after each loop.
Maybe the pan unit (especially if mounted to a ball head) might shift position over time...ball head not 100% tightened and gets loose.

Unless your motors skip steps, the keyframe locations of the motors itself should not change (excluding the mechanical effects mentioned above). Maybe you need to set a higher motor current and work with 0% energy save if the motors might skip steps.

For the issue with the slide controls in the app, I don't think we can do much. As I explained in a previous post, we are limited by the resolution of the slide controls of Android and iOS. We have 100 steps that these slide controls can distinguish. And if you have the motor speed at a high value, each one of these slide control steps, gets larger - resulting in the smallest speed increment the motors will react to. When you decrease the max motor speed, each of the slide control steps gets smaller, and your motors will start moving earlier with a smaller speed.