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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!
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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.
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#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.
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#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

#8 Andrea B.

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Posted 25 April 2017 - 07:07

Very quick comment. They are both forsythia as B. said. Look at the centers. There are short-petaled and long-petaled cultivars. See, for example: http://www.naturehil...orsythia-bushes

And -- excellent wavelength-to-color display. Matches my various findings over the years. Nice to see it displayed in a strip format for comparisons. But what do you mean by "not white balanced" ?? Just curious. :)
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#9 Mark

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Posted 26 April 2017 - 22:01

@Andrea: This is my error, albeit one I knowingly make in the absence of an equivalent term for this PP action. I understand its practically a misnomer to use the term 'white-balance' in regard to color correction of an image which is composed of wavelengths outside of the VIS spectrum (wherein there is by definition no 'white') - as in these UV images. Maybe 'invisible to visible color translation correction' would be better. "ITVCTC". Oh boy.

As I shoot in RAW, the coloration of the UV images I get SOOC are, well, quite inviting of PP'ing. Pointedly, my D750 captures ~365 nm UV with a highly saturated RED channel - though this isn't difficult to "white balance", especially since I've discovered how effective NX-D is with NEF files (go figure). For example, here is a sample from the above images before (left) and after (right) white-balancing in NX-D:
Attached Image: nonWB-v-WB.jpg

I know I could aid in this color-correction process by setting a custom in-camera WB, but since I shoot multispectral sets so often its just as easy for me to shoot in a default color space and do the adjustments in PP.

Also, if there is a more appropriate term I should be using... please let me know and I'll make sure to get it right moving forward.

#10 Andrea B.

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Posted 27 April 2017 - 08:48

Mark, sorry if I led you to believe that there was some error in your use of the phrase "white balance". There was not. We use that phrase for UV work just as we do for Visible work because "white" is that "color" which reflects all incident wavelengths, UV/IR included. :D

What I was attempting to ask is this: if your displayed images were "not white balanced", then what camera setting were you using? Auto, incandescent, direct sunlight?

(Your analysis of the red/blue ratios might perhaps be better done using Raw Digger to compare histograms of the RGB channel recordings. It avoids the all camera settings for white balance.)
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#11 Mark

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Posted 27 April 2017 - 15:45

@Andrea: I understand. I tend to operate under the standard definition of color being that which is in the [human] visible spectrum, with white being the sum of equivalent amounts of across the spectrum. Still, as you've seen, I do say things like 'white balance' in reference to invisible wavelengths. And I all too often say 'light source' when referring to UV and/or IR radiation, when I know it is not actually 'light'. I teeter between wanting to present with technically correct terminology, and just plain wanting to speak casually about really cool looking photos. I guess at least a modicum of consistency on my behalf would be nice :)

The camera setting I use while shooting RAW is, ?, I'm not actually sure. I think I have it set at AUTO1, or some such default preset. I've actually made and set custom presets for UV, VIS, and IR shooting, but that requires that I remember to go in and change the WB preset for each shot (when I shoot multispectral sets). I know its not really a lot of work (especially since the D750 has a dedicated button to load WB settings). But its just one more thing to juggle (and easy to forget) in addition to changing filters, "light" sources, exposure settings, focus, etc. And since I now have a pretty good, roughly standard workflow in PP, its easier to leave it on one setting and focus on other things while shooting. Besides, I figure that since I'm shooting RAW the in-camera development settings don't matter anyway, as the image data is not permanently changed in any way before getting the files onto my computer for PP. I actually find the workup of RAW files in PP a very satisfying experience. I never worked with film myself, but I might guess that my sentiment towards RAW PP development is akin to the experience of developing film in a dark room; which I've heard enthusiasts speak of with what sounds like a similar fervor.

I'd like to try Raw Digger, but last I checked it was a paid application. I don't contend in any way that it shouldn't be paid for - I'm sure it is deserving of pay - I just don't know that I have enough use for such an application at the moment to warrant the purchase. I'm sure I'll revisit it again if I find myself considering it often enough.

Edited by Mark, 27 April 2017 - 15:48.


#12 Andy Perrin

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Posted 27 April 2017 - 16:38

View PostMark, on 27 April 2017 - 15:45, said:

And I all too often say 'light source' when referring to UV and/or IR radiation, when I know it is not actually 'light'.

I think most scientists do use "light" for all types of radiation? That's why we qualify it with "visible" when that's what's intended. Otherwise it would be redundant.

What program is PP, by the way?

#13 Mark

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Posted 27 April 2017 - 17:57

@Andy: I work almost exclusively with research scientists and engineers - and I would be quite mindful not to allow myself the embarrassing misstep of calling > or < VIS radiation "light". But then, at work aren't we all mindful to be on our best game anyway? Maybe I just carry some of that over to the forums here in my after-work hours. I would of course like to hold this hobby of mine as a more casual, pleasant endeavor - hoping it never gets to feel like 'work', but instead keeps its fun for me.

PP isn't a program/application, its just an abbreviation: post-process.

#14 Andy Perrin

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Posted 27 April 2017 - 19:43

@Mark, I'm an engineer, and I've never been corrected for talking about "infrared light" or "ultraviolet light" as opposed to "infrared radiation," etc. I think your colleagues may be a bit strict!

Edit: Google Scholar turns up 655,000 results for "infrared radiation" (using the quotation marks in the search), and 600,000 results for "infrared light." That's close enough that I think we can say they are synonyms. Corresponding results for UV are 1.77 million for "ultraviolet light" and 1.19 million for "ultraviolet radiation."

Edited by Andy Perrin, 27 April 2017 - 19:59.


#15 Andrea B.

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Posted 27 April 2017 - 21:02

Relationships in the universe are all relative, yes? So while ultraviolight radiation may not be "light" to some humans, it is certainly light to some non-human living creatures. And while UV may not be a "color" to us, it is a color to them. So you can draw the line here -- or you can draw it there.

Here on UVP, we typically use such terminology relative to the context of Ultraviolet photography. That may be a somewhat more casual or slightly different usage than at school or at work. Anyway, just use what terms you are comfortable with here. If we cannot figure out what you are saying, we'll ask. :D

These days my concept of "white" has expanded from the Physics 100 definition (learned all those many, many years ago!). I can only think of white now as Spectralon White. B)

Mark, I'm happy you are enjoying the conversion & editing of raw UV files. It can indeed be quite satisfying to extract a nice presentation of UV tones and false colours.

I figure that since I'm shooting RAW the in-camera development settings don't matter anyway.

If shooting a Nikon and converting in NX2, NX-D or View NX-Whatever (not sure what we currently have with View), then all in-camera settings are preserved and thus can be quite useful. For example, I've found that using in-camera ADL can give the shadows a boost in some UV photos. Also, I use a kind of near-uniWB setting which usually enables better focusing and also faster speeds (thus less noise). And I always use a Neutral Picture Control to reduce excess saturation (usually in the red channel, of course) because it is easier to see if you have captured details while shooting.

Many conversion apps can do a fine job of "reading" Nikon in-camera settings. Some apps do not do this so well (Adobe, I'm pointing at you!!). But the point is -->> a good choice of Nikon in-camera settings will help you get a better file even when using an app which does not support those settings.

[And we can make a similar statement for any other camera brand. Use good in-camera settings to make the shooting easier and to produce a better raw file.]

I think everyone probably already knows what I'm getting at here, but I try to sometimes elaborate a bit for any newbs who may be reading. Skip it if you've heard it all before!!!
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#16 Mark

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Posted 27 April 2017 - 22:32

@Andy: Its not so much that my colleagues are strict - we don't even work in the context of light physics (for the most part), so its not even a thing that it would come up. I just mean that I would personally be embarrassed to get something technically wrong in a pointedly technical environment. And thank you for that google result - the context is perfect for a coincidental conversation I've been having with a friend about how just because everyone else is doing [any given thing], doesn't make it right. I'm probably most hard on myself, in this and other contexts; but then I do justify that for the sake of self improvement (or at least trying to remain diligent in the pursuit thereof).

@Andrea: I wonder about RAW files and how images can be quantitatively analyzed. Aside from Raw Digger are there other applications you know of which can help glean a fundamental understanding of raw (or processed) image data. I'm not thinking anything in particular, just curious to learn what other ways there may be to look at the data.

#17 Andrea B.

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Posted 30 April 2017 - 09:34

Link to WikiP entry about Dcraw, an open source, free app: https://en.wikipedia.org/wiki/Dcraw
Link to Dcraw app: http://www.cybercom....~dcoffin/dcraw/

Most open source photo software (and some which are paid) is built over the Dcraw app. Dcraw itself is used on the command line (as we used to say in Unixland), i.e., in your laptop's Terminal app. Dcraw has several inputs to extract data from a raw photo file.

***********

....just because everyone else is doing [any given thing], doesn't make it right.

But it is important to remember that scientific definitions can be fluid. As we learn more, the original definition sometimes changes. Example in point: we still do not have a definite point of division between UV and Visible light, for example. 380 nm? 390 nm? 400 nm? After all, most of us can see a bit below 400 nm. I suspect that 400 nm is the usually accepted marker for radiation vs. "light" because it is a nice round number. :D

To a mathematician (....ahem....former mathematician?? ) the only well-defined terms and hypotheses are in mathematics. All the rest of you all are just a little vague in your definitions. :D :D :D

This is an interesting discussion, but enough for now of my 2$. (We can no longer write "2 cents" because of monetary inflation.)
Andrea G. Blum
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