Dear Dr. Troscianko and collaborators,
First of all, thank you for creating the MICA and the QCPA! The prospect of being able to use UV-Visible pictures to analyze animal coloration is exciting.
I would like to use the MICA to analyze some UV-Visible pictures that we took in the lab some time ago with a UV-Visible lamp that we had at disposition at that moment: the OSRAM Ultravitalux Lamp spectrum and details.
I read the guidelines here on the website about illuminant spectra and I fear that the OSRAM spikey peaks will complicate the analysis as one of the symptoms of those peaks, the unnatural color, is clearly showing in our pictures (raws show a strong green bias).
I plan to ask Dr. Savazzi for the spectrum of the lamp and use that to calibrate the pictures, however I was wondering if there are any further steps I could take to model this illuminant in the MICA environment.
I thank you in advance for your attention! Best regards,
I’m really sorry I missed this question earlier! Actually I don’t think those peaks look too problematic. There are nice continuous emissions between the peaks, and the peaks are quite close together (a typical receptor will cover many peaks). I wouldn’t worry at all about this light source in terms of creating a decent cone-catch model. Just check the R^2 values it shows, and if these are low (e.g. <~0.97) then metamerism from the light source might be problematic.
The spectrum is all you need for creating the model.
Have a look at http://www.exo-terra.com/en/products/sunray_bulb.php for a full-spectrum solution
Hmm, the spikes indeed look problematic. Sorry for the late response, I only noticed this one just then. Do you have any way of testing if the cone catches from the MICA output correlate with manually calculated cone catches using spectral measurements? That would be my recommendation to quantify the issue. Depending on what you are aiming to measure and how, the nature of the bias introduced by the light may or may not be that big of an issue. If there is a systematic shift then you might be able to correct for it, or, if you are only interested in relative comparisons (i.e. X has 20% more UV reflectance than Y) just acknowledge that you are making that statement being aware of the bias. I guess Jolyon would have recommendations too. As you say, the best is to avoid such issues in the first place.
Apologies, the spikes are actually very narrow, so on second thought, I’d revise my consideration on them being problematic.
Hi Jolyon and Cedric! First of all I apologize for the late reply and I thank you very much for your suggestions! I tried what Jolyon suggested and the R^2 seemed to be particularly low, I do not have the values here at hand, but they were below 0.97 for sure. Therefore it might be a case of metamerism as Jolyon suggested. Just to be on the safe side in the future I decided to buy the Iwasaki eyecolour lamp but unfortunately it seems it has been discontinued. Would you have other suggestions for good Illuminants? I thank you very much again for your help!