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UltravioletPhotography

Helianthus (nectar guides)


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Yesterday I purchased this flower, hoping it had nectar guides. I was right.

 

Full-spectrum Panasonic DMC-F3

 

ZWB2 (2 mm) + chinese BG39 (2 mm)

 

F-stop: f/2.8, ISO 400, 1/8 s exposure.

post-284-0-03200500-1589805142.jpg

 

There is a little green flare in the bottom-left corner I have to fix. It is due to a slight light leakage.

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Andy Perrin
Stefano, when you redo the photo to fix the leak, you should expose for longer — I am finding this image really dim on both my phone and laptop.
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I usually use this settings to avoid overexposing bright things such as the sky and a paper tissue I use to set the WB. I will redo it at maybe ISO 800 or higher (the exposure is already at max).
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Stefano, that is a good foto if you open up the dark center area of the flower just a bit. I can show you if you grant me permission to download and alter your foto with a small shadow lift. Is that OK with you?

 

Helianthus (sunflowers), like Rudbeckia, have UV-dark central bulls-eyes. The amount of UV-absorbing area at the base of the rays ("petals") varies by Helianthus species. The false yellow in Helianthus sometimes intense, sometimes very pale. This example is quite lovely because of the two UV-light stripes on the rays.

 

Don't forget to flip the flower over and make a UV photograph of the back. It can be surprising. Sometimes there are stripes or false blue.

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Stefano, that is a good foto if you open up the dark center area of the flower just a bit. I can show you if you grant me permission to download and alter your foto with a small shadow lift. Is that OK with you?

There’s no problem.
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Don't forget to flip the flower over and make a UV photograph of the back. It can be surprising. Sometimes there are stripes or false blue.

I will try it.
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This one was taken today:

 

F-stop: f/2.8, ISO 1600, 1/8 s exposure.

post-284-0-80006600-1589914580.jpg

 

Believe it or not, this one below was taken before the photo above, using the same WB. I still don't understand why my WB changes if I change the ISO. It is quite annoying. I know the image will be dark.

 

F-stop: f/2.8, ISO 400, 1/8 s exposure.

post-284-0-01423200-1589914840.jpg

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Thanks, Stefano. I wanted to show you a bit of processing technique which I sometimes use to bring out the details of the reflected UV flower. I lifted the shadows a bit and slightly increased the contrast for the center. I applied a bit of sharpening to the center. This all has to be done carefully on the raw file for best results so that the dark UV areas are not overly brightened.

 

If for some reason you decide to study botanical photography instead of physics or math, you now have a start on processing techniques. :lol: :lol: :lol:

 

stefanoSunflower.jpg

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P.S. If the ISO is increased on your NEX Lumix then a noise reduction algorithm probably kicks in. I'm thinking this could potentially alter your white balance. I do not know if the NEX Lumix DMC-F3 has a noise setting which can be turned on/off, but do go look and see. On small point-and-shoot cameras, there are often a lot of JPG "improvement" algorithms to produce "best" results. Those are of dubious value for scientific work where you are trying to capture exactly what you see (or the filter/lens sees).

 

 

Editor's Note: Sometime I cannot think and type at the same time! Wrote NEX instead of Lumix.

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Don't understand the question.

 

Oh, I am a total AIRHEAD today!!! I wrote NEX instead of LUMIX!!! And then when David posted the link and I went and looked at it, I *still* did not see the typo.

:lol: :lol: :lol: :lol:

 

I will go correct that.

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Why "NEX"? Is that its complete name?

 

I think Andrea was hoping you got a Sony camera with interchangeable lens. The NEX line has an E-mount and APS-C sensor.

A new member self converted a NEX 5, and I think Andrea brain had that on the back burner, when she wrote this.

 

I think you should get a used Em1mk1 if you can swing it. The used price is down to $200. Add a Sigma 30mm art f2.8 for $100 and you would be able to get excellent results.

But that being said all Old Olympus cameras have weak UV filtering that I know of from the Em5mk2 and back. I haven't tested newer cameras. So you might also be able to get an old Olympus Pen camera for $50 now.

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