9 replies to this topic

[Andy Perrin]

This flower, which I'm initially categorizing as a daisy fleabane, showed unique patterns in all four bands that were tested. The visible, UV, and NIR responses are well-known, but I'm not sure the SWIR response (1500-1600nm) has been visualized before. As can be seen below, the ray petals seem to be light gray, and the disk is very dark, with white flecks. My intent is to get a filter wheel soon and make "true color" SWIR photos using three sub-bands. This flower is high on my list of ones I would like to see in color SWIR!

halogen, Sony A7S, Noflexar 35mm/3.5, BG38 2mm, F16 1.6" iso80
contrast adjusted


ConvoyS2+, Sony A7S, Noflexar 35mm/3.5, S8612 1.75mm + UG11 2mm, F16 iso1000 15"
saturation boosted, contrast adjusted


halogen, Sony A7S, Noflexar 35mm/3.5, generic 1000nm longpass, F16 iso100 2"
contrast adjusted


halogen, TriWave Ge-CMOS, Kowa LM12HC-SW 12.5mm/1.4, 1500-1600nm Thorlabs filter, F1.4 gain=0.5 0.033"
focal stacked, denoised, contrast adjusted, sharpened

Edited by Andy Perrin, 12 June 2019 - 16:34.

[JMC]

Thanks for sharing Andy. I wonder if water levels are a factor here, with darker parts of the image corresponding to more water?

[Andy Perrin]

Honestly I don’t think that’s the case. It’s certainly like that in the leaves (you can even see where the water is blocked in leaves), but here you can see the flower head has both black and white disk flowers (I hope that is the term— the white dots on the center edge I mean) and I doubt the hydration level is all that different between them. Trying to attribute everything in SWIR to the water absorption is probably a bad idea.

I could try an experiment? I could leave one to dry out over several days and see if the colors change.

Sugar is dark in SWIR, and also other things with -OH bonds. I wonder if that is related.

Edited by Andy Perrin, 13 June 2019 - 14:32.

[JMC]

You're probably right Andy. What little I know about SWIR (and it is only a little) is from what I have seen from it being used for skin imaging, where water level is hugely important. No reason at all why other components shouldn't have a huge impact on absorbance. As you say, alcohols and sugars with OH groups could be a factor.

Looking forward to seeing any other experiments you do.

[dabateman]

Andy,
Interesting, you maybe correct in thinking its the sugars a dry out test would show that if you can keep it flat.
After my recent spectral test I think the sugars play a large part in the darkness we see with UV.

[Andrea B.]

Very interesting! I don't recall any floral SWIR photos here by anyone else. (Corrections always welcome by me!) So you might be opening up an whole new area! Cool!

That is indeed one of the Erigeron species. The stem and leaves must also be looked at to determine which one. Your UV and IR photos correspond to what I've seen with Erigeron. No particular "patterning". Although as Birna (PhD botanist) has so often reminded me, lack of a "pattern" constitutes a pattern. Usually I get a dark false blue with Erigeron.

These three are common in the Northeastern US.
Erigeron annuus [Daisy Fleabane]
Erigeron strigosus [Rough Fleabane]
Erigeron philadelphicus [Philadelphia Fleabane]

Added: could also be Erigeron pulchellus

If you could get a photo of the leaves and stem, then I could perhaps nail down the ID and give this Erigeron a place in the Botanical section. It would be good to have a SWIR there. I'm always in hope that the photos will prove useful to someone someday. Indeed, we have had the occasional PhD requests for a UV floral signature. So at least some students have benefited.

[Andy Perrin]

Quote

Very interesting! I don't recall any floral SWIR photos here by anyone else. (Corrections always welcome by me!) So you might be opening up an whole new area! Cool!

Yes, I think all the SWIR flower patterns are undocumented so far, except by me. While it is kind of fun to have this whole area to myself for the moment, I do hope eventually other members will join me in SWIR. If nothing else, I would love someone to swap technical info with.

[Andrea B.]

I could certainly see myself getting into a bit of SWIR. Once I'm resettled out west, that is. There I'll have a whole new set of flowers to play with. I've documented some of them on a couple of desert trips, but now I'll get to cover them more deeply. So why not include SWIR in the Vis, UV, Fluor and IR documentation?

If you would enjoy it - and if you have time - you could write up a SWIR Sticky for UVP covering the basic gear and basic processing. If you do, then I'll "pin" it in the reference section.

[Andy Perrin]

Another example. This may not be the exact same species, the ray flowers look a bit different to me.

The SWIR was done with the Wollansak 25mm lens this time.

Edited by Andy Perrin, 01 July 2019 - 23:48.

[Andrea B.]

This one could be Erigeron philadelphus, which typically shows some pink.

Again the open disk flowers have the SWIR-bright anthers/pollen. Quite interesting.