Knowledge Base

Lighting Conditions

General

Generally, for optimal tracking it is important that the contrast between the subject and the background is as good as possible. For marker tracking, EthoVision XT needs to be able to distinguish the different marker colors. For both issues, the lighting conditions play an important role.

• It must be bright enough. A low light intensity can result in a suboptimal contrast between the animal and the background, and therefore tracking might not be optimal. Furthermore, a low light intensity makes it difficult to separate different colors. When it is not possible to use strong illumination in your setup, try using fluorescent marker colors with UV lighting.
• It must be even. The light source should be diffuse, for example, a shaded fluorescent tube or globe-type incandescent bulbs. This way, the contrast between the animal and the subject and the intensity of the marker color are the same throughout the arena.
• Shadows must be avoided. To avoid shadows, do not point the light directly at your animals, but instead toward the walls or ceiling. Use several lamps to obtain an even illumination.

Full-Spectrum Lights

For optimal color separation, illuminate your setup with lamps that approximate daylight in frequency distribution of wavelengths, that is, have a full-spectrum range. There is no technical definition of "full spectrum," therefore it cannot be measured. However, to compare full-spectrum lights you can directly compare spectral distributions.

In practice, full-spectrum lights can be recognized from two parameters:

• High Color Temperature (measured in degrees Kelvin). Usually higher than 5000 ºK. Values of color temperature around 2500–3000 ºK are typical of "warm" color lights (yellowish), for example incandescent bulbs.
• High Color Rendering Index (expressed as percentage). Higher than 95. A value of 100 represents the ideal or natural light.

Source: EthoVision XT 19 Help - Using Digital Video, Noldus Information Technology