I recorded a shot using a slider that runs parallel to a furnishing, and there are some issues with the final take. There was some vibration, which is no problem at all, but what is bothering me is that the slider goes slightly upwards, then downwards, just to finally go upwards again. It is slight, but it is there and I need to delete it before finishing the cut.
I have tried with mocha and the various stabilizing options in AE, but I am yet to find a solution to delete that undesired motion and make the slider run perfectly linear and parallel to the furnishing. So, what can I do about it?
I suggest creating a 2-pixel-wide mask at the middle of the footage that reveals the vertical position of the furnishing. Use Stabilize Motion with a 2-pixel-wide-tracker on the masked layer and capture the vertical motion, then apply it.
I am not sure I am following you. I have my composition with the footage. How do I create the mask? Do I create a solid of 2x1px, or do I have to duplicate the footage layer and use a mask on it? Do I have to pre compose it?
I reckon that I have to use said mask as the tracker's target, haven't I?
1) Create a new comp (Comp1) using your footage
2) Create a few pixels wide, vertical mask slice.
3) Create a new comp (Comp2) using `Comp1`
4) Stabilize Motion in Comp2
5) Copy Anchor Position of `Comp1` layer in Comp2
6) Return to Comp1 and paste on to the footage layer.
That should stabilize your footage* vertically.
*(I'm assuming the `furnishing` you have captured has an upper edge with enough contrast)
For instance, if your footage is 1920x1080, a rectangle mask of 2x1080 positioned at the center of the frame will reveal only a slice of a video frame so the motion tracker will capture the vertical movement only.
Lets say the background is white and the shelf is red. You said the shelf moves up and down while the slider moves across. When you playback the footage, the masked image will look like a thermometer indicator moving up and down. If you track the upper red edge, you'll capture the vertical motion of the shelf.
I find myself with another problem, though. There is a slight increase and decrease of velocity at the beginning and the end of the shot, which isn't a problem, but there are also variations in the speed through the movement. Now I need it to have the same velocity during the 10 seconds of its length.
I am going crazy with the time stretch tool, so I wonder if there is a less complicated and more precise way of doing this.
About the velocity issue; I don't know any easy solutions for that.
I suggest using Time-Remapping tool instead of Time Stretch.
(I am assuming you are able to locate the exact position of the slider camera by eye observation.)
Lets say your footage has 100 frames.
Enable Time-Remapping and add key frames at frame 1 and 100.
Jog to the point where you think the slider camera is at the middle of the slider path and add a key frame there.
This key frame should be at the 50th frame if the footage was captured with a constant slider speed. Move the key frame to the 50th frame to fix the time shift.
Repeat this procedure for sections between frame (1-50), (50-100).
If the problem still exists, repeat for sections (1-25), (25-50), (50-75), (75-100)...
You get the idea... Repeat until you go crazy.