My research focuses on predation risk in burned versus unburned areas, particularly looking at the Western Fence Lizard (Sceloporus occidentalis) and its ability to background match dark burned substrates after a wildfire. To quantify color overlap, we took photos of lizards in the field and utilized the Quantitative Color and Pattern Analysis (QCPA) framework within the micaToolbox plugin in ImageJ to account for how avian predators view the lizards. This allowed us to generate color maps illustrating the lizard’s camouflage effectiveness against substrates. However, I am specifically interested in measuring the “darkness” of lizards in the photos.
What in the RNL metrics represents luminance would this be saturation? From our current output, we get X(red-green wavelengths), Y (yellow-blue wavelengths), and Saturation. So would the “darkness” be the saturation metric? Also, to verify, would the dbl channel in the bluetit model be the luminance? To add, we are not incorporating UV vision.
Heya,
While saturation is inherently linked with brightness perception, it doesn’t equate to measuring brightness contrast per se. The RNL equivalent you are looking for is the luminance delta-S value that can be calculated between two stimuli based on the luminance channel’s stimulation.
Note that, unlike chromaticity, this can’t be calculated for an individual stimulus. To get an approximation of the perceived brightness of an animal, you would indeed be interested in the relative stimulation of its luminance contrast detecting channel (e.g. the double cone in birds).
Cheers,
Cedric