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Greetings from Žatec

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#1 Martin Zitko

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Posted 24 April 2018 - 10:56

Hello,

I've been lurking around here for a year or so and this site has helped me tremendously while working on my bachelor's thesis. Now I study Theoretical and evolutionary biology in the Department of Philosophy and History of Science of Faculty of Science, Charles University. Currently I work on my master's thesis that is going to be about ecological factors influencing ultraviolet signatures of plants. And since I learnt a lot here I also thought about giving something back if my work should lead somewhere. I consider this as my stepping-stone to my long-standing interest in appearance of plants.
This was one of the first plants i ever made a photo of, presumably Potentilla arenaria. I look forward to any suggestions in regard to my work.

Cheers, Martin

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  • Attached Image: net.jpg


#2 nfoto

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Posted 24 April 2018 - 11:42

Heartily welcome to UVP. You'll find a lot of stuff and discussions that should interest you here and we do hope you'll make your own contributions as well :D

The UV signature of your Potentilla arenaria is the "classic" one for this genus. However, many species do show their own variations over a common theme as regard the size and appearance of the UV-dark patches.

Your UV image is apparently severely underexposed. You should reprocess the raw file to bring details better out. Or perhaps make a new capture?
Bjørn Birna Rørslett, Ph.D.
Just call me Birna

#3 Andrea B.

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Posted 24 April 2018 - 16:49

Hello Martin and welcome to UVP. We will certainly welcome your contributions to the botanical section of our site if you would like to post something there.

Your studies sound so interesting! It is good to see someone considering UV in a thesis topic. We will be happy to answer any questions about editing or processing or anything else about UV matters. On UVP we use a standard "click-white" for botanical false colors so that the flower's or plant's look will be the same across different gear platforms. It has proven useful for bringing out the details of a flower's appearance in UV.


(A reminder: The photographer always retains ownership and copyright for any photographs posted on UVP.)
Andrea G. Blum
Often found hanging out with flowers & bees.

#4 Martin Zitko

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Posted 25 April 2018 - 23:18

Thank you for your kind words. I tried to go back and reprocess the raw file as you mentioned. I feel it's a little bit better. Though I will definitely try to take it again.
I am kind of ashamed because I never touched a camera before venturing into this project ... :rolleyes: I feel like I don't know what I am doing half the time.

I will be happy to make contributions to the botanical section, actually I am leaving for the south Balkan very soon and I hope I will make a bunch of photos there. Regarding the "click-white" ... Do I understand it correctly that one should make one referential photo of a white UV standard before every session and use this for the reference click-white clicking? (I didn't have it for this Potentilla session yet, so I used it kind of retroactively.)

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  • Attached Image: pot_ar2.jpg


#5 Andy Perrin

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Posted 25 April 2018 - 23:21

I love that reprocessed version. The flower really stands out against the dark background.

#6 Andrea B.

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Posted 26 April 2018 - 15:30

I feel like I don't know what I am doing half the time.

We ALL started out that way. You will learn!! Digital cameras make it easier because you get instant feedback. You can shoot hundereds of photos to test out how settings and filters all work, then just delete them.


Regarding the "click-white" ... Do I understand it correctly that one should make one referential photo of a white UV standard before every session

If you would like to standardize the output of your UV false color photos, then using a UV-stable white standard is the best way. I would suggest PTFE as the least expensive option. Look here for more information: <> Sticky :: White Balance in UV/IR Photography <>

If we know the details of a photograph, we can perhaps better help you? Usually we post the camera, lens and filter information along with the exposure data next to a photo.
Andrea G. Blum
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#7 nfoto

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Posted 26 April 2018 - 23:23

I had a look at your Potentilla photo. Besides the obvious underexposure, apparently there is massive flare or even a light leak on the right hand side. This could be a leak through the viewfinder, the filter mount, or lens/mount adapter.

A very quick (30 secs) fix and some brightening delivered this, which I guess is close to what one would expect from such a species and its growing conditions.

Attached Image: potentilla arenaria edit.jpg.jpg

I have removed the colour artefacts from the light leak.
Bjørn Birna Rørslett, Ph.D.
Just call me Birna

#8 Martin Zitko

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Posted 18 May 2018 - 19:31

Thank you all for your suggestions. (That's like a real magic, what you did with the photo :) ). I think it is really a light leak probably from the lens adapter because when I use my other lens, everything seems fine to me.This is a photo of Convolvulus holosericeus from F.Y.R.O.M. If you think it's good enough I could add it to the botanical section.

Visible image: Nikon D40, Optomax 35mm f3.5, ISO 200 1/40 sec
UV Image: Nikon D40, Optomax 35mm f3.5, Baader U-Venus-Filter 2", ISO 200 2 sec

Attached Image: con_hol.jpg

#9 Andrea B.

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Posted 21 May 2018 - 15:36

Hi Martin -- Yes I would very much like having your Convolvulus holosericeus in the botanical section. It is quite nice. And illustrates very well a UV absorbing visibly white flower. You can make the post and later I will review the format and make any minor edits if they are needed.

It has been rather busy on the forum recently (and in my "real" life). So my apologies for not responding sooner. :)

BTW, Martin, it is known that central bullseye signatures for a fixed species can be larger/smaller depending on altitude and geographical location. So you might want to look for those studies and look to see whether the authors have any suggestions for further research.
Here is one link to such a paper.
https://www.ncbi.nlm...pubmed/26909439
Andrea G. Blum
Often found hanging out with flowers & bees.