The first two tools are used to mark the first and last frame for analysis, and the green tick tool to start analysis
Analysis: Two measures of movement are analyzed. Both methods report the difference between successive frames.
Comparison of methods:
- For each frame, the
difference in position of the first light/dark interface is
determined. The measurement can start either at the light or dark end
of the line (Menu Options | Begin at ...). A value of -1 indicates no interface found.
- The mean square of the differences in intensity at each pixel along the line is calculated
- Method 1 provides a measure in pixels, and so can be converted to actual scale
- Method 2 is much more sensitive than method (1).
- Method 2 is sensitive to changes in light intensity, but this is much less true of method 1
- If the target drifts slowly, neither method gives much change compared with sudden movements, eg muscle contractions
Page written by Chris Elliott (firstname.lastname@example.org) 29 Sept 05