• Ultraviolet Photography

Evening primrose (Vis, UV, UVIVF, SWIR)

Fluorescence Infrared Multispectral SWIR
6 replies to this topic

#1 Andy Perrin


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Posted 02 July 2019 - 19:21

This seems to be an evening primrose (of which there are a number of species) or something like that. It was photographed around midnight, so I suppose it is living up to the name.

Cameras: Sony A7S for visible, UV, and UVIVF, TriWave Ge-CMOS for SWIR (1500-1600nm)

Lighting: halogen for visible and SWIR, filtered Convoy S2+ for UV and UVIVF

Filters: for UV, S8612 1.75mm + UG11 2mm (although none was really needed since the torch is filtered also, but it's my standard stack)
for visible and UVIVF: BG38 2mm + Hoya UVIR cut
for SWIR: 1500nm long pass from Thorlabs (FEL1500)

Attached Image: _DSC2360 visible UVP.jpg

Attached Image: _DSC2363 UV UVP.jpg

[note: do not give me any grief about the damn white balance. My EYES don't even see the same colors as the rest of the board, how do you expect me to get it right? I made it look pretty.]
Attached Image: _DSC2361 UVIVF UVP.jpg

SWIR (1500-1600nm)
Attached Image: yellow flower focal stack SWIR crop_res.png

The SWIR patterning is quite interesting as it has aspects of the UV pattern here too, but is not identical, as the SWIR shows a dark bulls-eye at the center which is not there in UV. Also the anthers are very reflective in the SWIR photo. We should probably keep in mind that this is just the 1500-1600nm SWIR band -- I have not investigated other sub-bands of SWIR yet:
Attached Image: compare UV SWIR UVP.jpg

#2 Cadmium


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Posted 03 July 2019 - 00:47

Some pretty interesting glittery stuff going on in that UV shot!

#3 Andy Perrin


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Posted 03 July 2019 - 01:12

Yeah, I thought that was the conical cells that people are always going on about in these parts?

#4 Mark


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Posted 04 July 2019 - 21:39

There could be some correlation of the dark areas in the SWIR images with higher water content levels. It may be interesting to photograph, in SWIR, a series of a given subject (e.g., a leaf) at different stages of hydration.

#5 Andy Perrin


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Posted 04 July 2019 - 22:06

Mark, I suggested that in the other thread (on daisy fleabane) but what’s stopping me is that the flower shrivels up as it dries which will make it hard to photograph petals.

#6 dabateman

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Posted 05 July 2019 - 00:12

Yes most flowers will close or fall apart when they dry out. I have a collection of dry flowers now.
The one that stayed in place was my daffodils. But the wild ones are all gone now. You may be able to buy one.

#7 Andrea B.

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Posted 06 July 2019 - 16:11

Andy, we can't give you any grief about the fluorescent WB
because we've never quite figured out what it "should" be. :D :D :D
We can standardize fluor WB if shot under certain conditions using the Target thingie,
but that's about it. So rest easy.

The Evening Primrose in UV shows iridescence on its 4-part stigma.
Conical cells are typically on petals or rays where they serve various functions.
That is a really good UV photo of this flower!

The SWIR signatures prove interesting-er and interesting-er the more you post.
Andrea G. Blum
Often found hanging out with flowers & bees.