NeuroMotive™ User’s Manual
LB-0336 Rev. 1.00
Page 24
Marker Threshold
To the right of the Marker Color Boxes are the Threshold Sliders. The numerical value of each threshold will
display when the mouse cursor hovers over a slider.
Color and luminance captured by
the camera change with ambient
and diffuse light present, and with
the area in the field of vision
occupied by the moving object.
Because of this, the marker color
and luminance may occupy a range
of values. The Threshold sliders
specify this range. If Luminance is
selected, the Threshold slider for
luminance is accessible. If Color is
selected, the Threshold sliders for
color can be adjusted. And if LED
is selected, both the Threshold
sliders for color and luminance are
available.
The Color Threshold slider specifies the degrees of tolerance in each direction of the color wheel from the marker
color (Figure 16). All color values greater than the marker color plus the color threshold, and less than the marker
color minus the color threshold are ignored by the software. Same holds on the greyscale if the image is non-color.
The Luminance Threshold slider specifies the tolerance on the greyscale (0 – 255) from the selected marker
luminance (Figure 16). All luminance values less than the marker luminance threshold are ignored by the tracker.
The LED Luminance slider value specifies the darkest value the tracker should consider. All luminance values less
than the LED Threshold are ignored by the tracker. And all those greater are maximized in brightness.
When using the Color Threshold sliders it is helpful to remember that the further to the right a slider is set, the
greater the range of colors that will be deemed to constitute the color value of the associated marker. When using the
Luminance Threshold, the further to the left the slider is set the less light is required to be above the threshold. This
leads to the possibility of false positives and the marker jumping around. When adjusting the sliders it is suggested
to use the Threshold view of NeuroMotive™ (
View->Processed Image->Threshold Markers
) to pinpoint when the
Tracking Markers appear. Using threshold view shows blobs that have been identified as potential markers. They
should be varying shades of grey and white against a black backdrop as shown in Figure 17. Adjust the threshold
sliders until only the markers are visible.
Figure 16 - Color, LED and Luminance Thresholds