I have been working on creating a custom cone-catch model for my system and I believe it has been pretty successful. However, when converting the cone-catch to an RNL chromaticity and measuring the mean X and Y values, I have only been able to get a mean X value. I believe that the lizard model I used is a trichromat but I thought it was still possible to get both an X and Y mean. In order to try and solve this issue, I added a luminance channel through the LW channel (based on the literature of my system, a lizard) and then was able to get both the X and Y means. I just wanted to double-check that this was a valid way to get that Y mean value. If I was interested in then measuring luminance, could I just use that Y mean as the luminance channel for the pattern and luminance measurement?
Thank you so much for all the help and for the great program!
Heya Kelly,
Please note that a visual system with n cone channels will have n-1 opponent channels as per the RNL model in it’s chromatic (original) form. Therefore, your model needs to produce both, an X and a Y opponent channel. If it doesn’t, then you might have an error in your visual model files (e.g. wrong order or naming of channels). Please also note that the luminance channel is processed separate for chromatic (traditional RNL model using all cone channels) and achromatic contrast (using the achromatic adaptation of the RNL model as per Siddiqi et al.). I hope this clarifies it. The easiest way to make sure the files are setup correctly is by using already functional trichromat files in the toolbox and substitute the values with those of your new system. That way you can be sure that formatting, naming etc. are likely without error.
Cheers,
Cedric
Heya,
Glad I could help. If you want luminance expressed as the % of cones stimulation the cone catch value of your luminance channel is the value you are after (not the same as luminance). If you re interested in the luminance as per the objective amount of light there is independent of what photoreceptor you point at it (given your light measuring device is not sampling the entire spectrum unlike a spectrophotometer), then the mean RGB value of your .mspec image is a better proxy. The pattern parameters in the QCPA distinguish between these two cases (i.e. parameters with ‘L’ = ‘Luminance’, parameters with ‘SL’ = ‘Siddiqi Luminance a.k.a. Luminance RNL a.k.a. Luminance JNDs a.k.a. Luminance delta-S’).
Cheers,
Cedric
Hey Cedric!
Thanks for the help, I think I figured it out.
In my past work I have only been using bluetit visual systems that already came with the luminance channel in the model so I never had to add one manually. Now that I have the lizard one, I added a luminance channel post cone-catch model and then ran the RNL-chromaticity. It worked great and now I have an X and Y mean! However, I just want to double check that when I want to calculate the luminance value, would I use that cone-catch model and select the ‘lum’ channel to get the luminance value?
Thank you so much!!