Hello,
I was wondering how I can \”see\” polarized light. And if mica Toolbox could work to analyze and quantify that.
I am interested in this because the flowers of the system I am working on (spiral gingers, orchid bees, and hermit hummingbirds) seem not to interact directly with pollinators by color. I think the color is secondary since bee-pollinated flowers can be red or have complex patterns (red flowers are typically known to attract hummingbirds in temperate systems). Hummingbird-pollinated flowers can be yellow (typically thought to attract bees in temperate systems). So I think I can figure out something by modeling polarized light.
Thanks,
Pedro Juarez
Sounds like a fascinating hypothesis!
The toolbox could certainly be modified to work with polarised light, though with some small customisation. First, you’ll need to take three or more photos with a linear polarising filter at three different angles (as close to 0, 45, and 90 degrees as possible). Then you need to create your own customised camera configuration file in ImageJ/plugins/micaToolbox/cameras
It might look something like this if you want all 9 slices saved, i.e. RGB for all angles (you’ll need to replace spaces with TABs and save the text file):
Photo R G B alignCh1 alignCh2
polarised0 1 2 3 0 0
polarised45 4 5 6 2 2
polarised90 7 8 9 2 2
In practice you might not be interested in the interaction between polarisation and colour, so just save the green channels:
Photo R G B alignCh1 alignCh2
polarised0 0 1 0 0 0
polarised45 0 2 0 2 2
polarised90 0 3 0 2 2
Then generate an mspec image, selecting the camera configuration file you’ve just made, and measure the calibrated images across all these angles and you’ll be able to work out the degree of polarisation and angle of polarisation in e.g. a spreadsheet from the image measurements. If you want to convert the images to avian double cone sensitivities (or any other cone-catch) that’s doable too, though again requires a little customisation, and the 9-channel RGB configuration at the top.
The evidence for polarisation vision birds is still by no means clear (possibly bound up with however their magnetoreception works), so it’s not immediately obvious that hummingbirds will be using it for flower detection. But inverts often have excellent polarisation vision, and e.g. butterflies use polarisation cues when finding host plants etc…