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Forsythia, maybe?

Multispectral
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#1 Mark

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Posted 20 April 2017 - 01:34

I'm taking a guess here on what this may be - and my guess is some species of Forsythia. I was surprised a search on the forums here didn't return any hits on that keyword. I clipped this twig with a bunch of flowers on it yesterday from a bush, about six feet high, in my sister's back yard here on the east coast of Massachusetts. These shrubs are common around here, and coming into bloom right about now.

I used a different setup than my usual to shoot the following multispectral set. For this set I used distance to remove the background from all of the shots. I also shot the UV and UVIVF images with LED only sources (as opposed to the fluorescent BL-B's I usually use). I still need to work on my technique, but I think its getting a little better.

All images: Nikon D750 [broadband mod]; 50mm Nikon Series-E + 20mm extension tube

VIS: 425nm longpass/GG435 longpass/Kolarivision IR-block stack; Sigma EF-500 DG Super flash; f11 / ISO320 / 0.6s
Attached Image: 04-19-2017_00-13-49.jpg

UVIVF: 425nm longpass/GG435 longpass/Kolarivision IR-block stack; 1 @ MTEU303+U340 & 1 @ MTEU303+FL02; f11 / ISO320 / 5.0s
Attached Image: 04-19-2017_00-10-09.jpg

UV: Asahi ZRR0340; 1 @ MTEU303+U340 & 1 @ MTEU303+FL02; f11 / ISO320 / 2.5s
Attached Image: 04-19-2017_00-25-25.jpg

IR: Xnite-830; 850nm Evolva LED torch; f11 / ISO320 / 0.25s
Attached Image: 04-19-2017_00-33-51.jpg

One additional note: This was my first opportunity to use two MTEU303 torches as my UV source. From this I learned that the gold color cast I've been seeing in my UV images using the MTEU303 torch is not actually from the torch itself, but rather from the U340 filter I put on the torch. The fluorescent BL-B I've used in the past does not generate this color. Pointedly, the second MTEU303 I now have, with an FL-02 filter on it, does not do this. Only when I put the U340 filter on either of the MTE torches does this color cast result. I'm not saying anything for or against it - its just an interesting effect (for now).

#2 Andrea B.

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Posted 20 April 2017 - 05:08

Yes, this is one of the Forsythias. Although it is a bit more orange than I typically see? Usually the flowers range from a pale, lemony yellow to a rich saturated yellow. This one has a bit of a Cheeto cast. :lol:

The fluorescent, glittery stripes on the petals are so cool! Don't you love surprises like that?

I have some UV Forsythia photos from past years which I've never gotten around to posting. Someday soon, I hope. You should make a UV-signature post with yours in the botanical section!
Andrea G. Blum
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#3 nfoto

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Posted 20 April 2017 - 07:53

The genus Forsythia is correct. Narrowing down to a specific species might not be possible though. These ornamental plants are mostly cultivars.

I have a large Forsythia at the entrance to my home. Still not coming into bloom as the spring so far has been very cold. My previous UV captures of it are very similar to those posted in this thread.
Bjørn Rørslett

#4 Mark

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Posted 22 April 2017 - 17:07

Now I'm second guessing my Forsythia guess. From my own backyard I snipped a small branch from what looks, at a glance, like the same kind of plant. But up close I see now the petals are a different shape (more typical of Forsythia?), and the UVIVF signature may be different. Do Forsythia species/phenotypes vary this much, or are these two (here and above) actually not both Forsythia?

While the IR image is comparably devoid of any interesting, contrasty features (IMO), the VIS image shows this one to be the more typical pale yellow Forsythia should be (?). And the petals are long and thinner as they should (?) be as well.
Attached Image: 04-22-2017_02-08-02_vis-ir.jpg

The overall UV reflectance looks essentially the same as the other plant. But the UVIVF view does not show the fluorescent stripes seen in the other plant. Also, the petals appear to have some kind of stain on them (?); which just happens to be fluorescent as well.
Attached Image: 04-22-2017_02-08-02_uv-uvivf.jpg

I wonder if that staining is perhaps mold, because I did pick this after a day or two of overcast skies and rain. Or maybe its just pollen, washed and smeared about by raindrops? I would re-test this today, but its still wet and raining here, so it will be another couple/few days before everything is dried out again.

#5 nfoto

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Posted 22 April 2017 - 17:42

Still Forsythia. As I already posted, there are many cultivars on the market.
Bjørn Rørslett

#6 Mark

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Posted 22 April 2017 - 19:11

@ All: Relating to the gold color cast in the UV images I referenced above, I've found that this is a function of the camera's interpretation of different UV wavelengths. Whether it develops in PP as gold/other is of course a function of white-balancing, particularly since I am not generally not standardizing for colorimetric comparisons, but rather for aesthetic presentation in any given capture. This series (not white-balanced) shows the Forsythia subject shot with a modified Nikon D750 + AndreaU-MKII filter, under UV wavelengths from 365 to 390 nm (unfiltered 5mm UV LEDs). Note that the last two images are 365 nm from two different MTEU303 torches, each fitted with a U340 filter. The chart below is just for a visual quantitative comparison, to get an idea of how much each differs, as a measure of the blue:red ratio.
Attached Image: 04-22-2017_12-28-48_LED-test.jpg

Attached Image: chart.gif

So, I found the gold color cast was from using two distinct UV wavelengths, where white-balancing one would lead to the gold color of the other (given my personal white-balancing preference/technique). For UV images I'll probably stick to either a single wavelength LED source, or a more continuous spectrum UV source (e.g., fluorescent bulb). For UVIVF images though, I'm happy to dump as much UV on a subject as I can get!

#7 Andy Perrin

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Posted 22 April 2017 - 21:31

Mark, I took advantage of the gold cast with this photo, assuming it's the same phenomenon (two light sources, torch and sunshine, in that case):
http://www.ultraviol...dpost__p__15467