APS Excellence in Physics Education Award
November 2019

Education Prize Logo
Science SPORE Prize
November 2011

NSF Logo
The Open Source Physics Project is supported by NSF DUE-0442581.

Switching the time column

Return to the Tracker forum
Login to post to this thread

Correcting the rolling shutter effect with adjusted time values
Axel Mellinger
2 Posts

Is there a way to use a different column as time stamp, and base the calculation of angle and angular velocity on that column? And could Tracker calculate derivatives of a quantity with non-uniform time steps?

Background: In one of our intro physics lab experiments, students are recording a video clip of a rotating disk. Tracing a point on the disk, they calculate angle vs. time and angular velocity vs. time. The webcam introduces a strong rolling shutter effect, which makes the (uncorrected) angular velocity appear to oscillate. However, this can be compensated by adjusting the time stamp of each video frame according to

t_corr = t - t_line * y

where t_line is the readout time for one line in the webcam image, and y is the vertical pixel coordinate. See here for how efficient this correction works: http://galaxy.phy.cmich.edu/~axel/PHY17x/Rolling_Shutter_Correction.mp4

At the moment, we use Logger Pro for the video analysis, which has, however, been discontinued, and we are looking into Tracker as a possible replacement. Is there any way this rolling shutter correction could be done within Tracker? Any suggestions would be highly appreciated!

Axel


Current Replies - View all
Re: Correcting the rollin...   (Douglas Brown - )
Re: Correcting the rollin...   (Axel Mellinger - )
Re: Correcting the rollin...   (Douglas Brown - )
Re: Correcting the rollin...   (Fernando Ferro - )
OSP Projects:
Open Source Physics - EJS Modeling
Tracker
Physlet Physics
Physlet Quantum Physics
STP Book