4 replies to this topic

[enricosavazzi]

Just a quick shot of unidentified crustose lichens that can be found everywhere on old stone drywalls on the island of Öland. They form visually featureless flat crusts that are white also in VIS in the dry state. They become somewhat less VIS-reflective when wet, but I have no comparison shot.

Mosses and other lichens on the same stone surfaces, in contrast, are UV-dark when dry. My guess is that, as far as UV is concerned, either absorption or reflection of UV in the surface layers is a good adaptive strategy to protect the living tissues underneath. In the VIS and NIR, a reflective (or white) surface could also be adaptive in lowering the temperature of the tissues during periods of high solar irradiation.

Full-spectrum Sony A7 II, Baader U, AI Nikkor 24 mm f/2.8. Somewhat underexposed to avoid saturation in the white areas.

[Andy Perrin]

I have taken many lovely lichen photos on the stone walls we have in New England everywhere also. They tend to show in bright purples in the false colors.

[Adrian]

This is really interesting. I have been doing some research on lichens recently, and have done some of my own UVF images, but as yet no UVR. Apparently lichens contain a variety of chemicals actually known as "lichen substances" which can act as sun (UV) blockers to enable them to grow in northern/Arctic regions. I understand research is ongoing by skin care companies about their possible use in sunscreens.
I would be really interested in seeing a visible light/UVR pair of images.

[Andy Perrin]

Adrian, scroll down here:
https://www.ultravio...dpost__p__12467

[enricosavazzi]

I noticed in shots at other locations that lichens are sometimes UV false blue. The lens I used to shoot the BW image I originally posted is not really good to produce UV false color, but it does indeed look like these lichens are not producing false blue but just a spectrally neutral bright reflection. I will try with a "real" UV lens when I have the chance.