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UV Allamanda with UV Quad LEDs & NO filter !


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UV Allamanda with UV Quad LEDs & NO filter !

No filter on the lens...!

I have been working on this 'vision' for two years & the fruits of success are paying off, thankfully.

 

Sigma fp full spectrum camera, Canon 40mm pancake lens, NO filters.

The Quad LED has 365, 375, 385 & 395nm LEDs at 90watts.

SOOC WB only.

 

post-31-0-59746400-1618647230.jpg

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Some nice definition there. As you said elsewhere, focus stacking would be useful.

 

I assume this is indoors so that you can block out all other light sources.

 

Surely the 285nm LED is redundant, isn't it? The lens won't pass that frequency and the sensor won't see it. Wouldn't it be btter to replace it with a longer wavelength LED?

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Some nice definition there. As you said elsewhere, focus stacking would be useful.

 

I assume this is indoors so that you can block out all other light sources.

 

Surely the 285nm LED is redundant, isn't it? The lens won't pass that frequency and the sensor won't see it. Wouldn't it be btter to replace it with a longer wavelength LED?

 

Thanks Bernard, 285 is a typo...will change to 385nm...pronto..

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Yes, I saw that topic, but what I am curious to see is if there is more chromaticity with the quad LED. A 365 nm LED is quite monochromatic, and for some this makes "less pretty" images than under a broad UV source like sunlight or a flash.
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I like the with Baader U filter one better.

I am surprised by the amount of green in your led only shot. It reminds me of a 1.5mm U330 filter image.

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I am trying to sleep....but

How do we decide where the green is coming from ?

Visible light or Bayer dyes reaction to UVA ?

The yellow can be UVA reaction on Bayer dye ?

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Thanks Stefano

I understand now...

Quad LEDs with the Badder UV on the lens....

post-31-0-06427700-1618665536.jpg

Thanks. I expected more colors, it could be that the flower is not very UV-colored.
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I am trying to sleep....but

How do we decide where the green is coming from ?

Visible light or Bayer dyes reaction to UVA ?

The yellow can be UVA reaction on Bayer dye ?

 

Since the Baader venus image isn't strong in green, I suspect your Leds leak into visible range. The camera is much more sensitive there. So any amount would hit the image with the glow you are seeing.

Also seeing a very small 520nm bump in UV leds isn't surprising. My flood 365nm leds were only 520 when the original polycarbonate lens was on the front filtering out all the true 370nm peak.

Solving that problem was fun and should have asked for a partial refund, but I forgot about it. The company was going to fully refund me if I smashed them to bits with a hammer. That still seems insane to me. But now after mailing stuff off to China, I kind of see why.

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I have been waiting to get a Straight Edge Gen3 from Reed, but he seems to have run into difficulties with them.

These cut steeper at the 390nm end, so would be ideal for the Quad LEDs.

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Col, please tell me what your white balance was when you made the first Allamanda photo above? That's a good photo, but I am curious about the color. Does Sigma have a raw mode so that the photo could be analyzed in an app like Raw Digger?

 

I'm trying to recall how one of the converted Nikons works with no filters under UV light.

No filters under UV light generally would produce fluorescence if shot in the dark.

But were you inside or outside when you made the photo? Was there ambient Infrared? Ambient Sunlight?

 

My general understanding about LEDs is that they do not "leak" outside their waveband. However, given the nearness of 385 nm and 395 nm to the visible violet and indigo blue, there could of course be some violet or blue. This does not normally hurt a UV floral photo because the reflectivity (alternately, absorption) curve does not usually contain a "sudden" steep rise or fall.

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Andy Perrin
LEDs won’t leak unless they are the kind that incorporate fluorescent bits to intentionally extend the spectrum.
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They can emit light due to self-induced fluorescence (this is how I understand it), for example a blue LED does emit also red light (I saw this with a diffracton grating), but the opposite does not occur. I don't know how much this could affect the picture.
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LEDs won’t leak unless they are the kind that incorporate fluorescent bits to intentionally extend the spectrum.

Could be intentionally or unintentionally as the levels do not need to be that high compared to the UV-intensity.

It could be enough that some part of the LED's structure has weak fluorescence.

 

White LEDs are made with intentional fluorescence, but thos can be something different.

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Stefano, are you sure that’s what it was? Could it have been the secondary spectrum?

I saw it with the naked eye. I can even take a picture later. There is this big blue peak that becomes weaker and covers the green, red and probably infrared portions of the spectrum. Same with a green LED.
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Andy Perrin
Ulf, have you ever seen that happen in your own spectroscopy of LEDs? (Wouldn’t they intentionally avoid that?) Stefano, I believe you saw something, I’m just questioning the interpretation.
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Yes I have. It was from a cheaper Chinese LED where the plastic casing emitted a secondary spectrum around the LEDs chip.

I do not think I can find the spectrogram as it was a long time ago.

In general this might happen with any structure in the build in the illumination setup, part of the LED or not.

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Thanks everybody, I'll read it over again later when I return home.

 

Andrea, can you PM me your email so I can send you a DropBox

I WB on the grey background,

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Colin the easiest way to know if your Led setup is leaking into visible or IR is to just hold your hand held spectrometer thingy to it or near by and see if you have a 520nm bump. That would be my guess.
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Yes there is a very tiny leak up to about 500nm.

I have another Allamanda flower & tomorrow I will use a 410nm cut filter on the camera.

 

post-31-0-40349000-1618915202.png

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Interesting,

So it's most a 380nm light with tail up to 450nm. Not what I was expecting, but may acount for what we are seeing.

Many flowers get excited with 405 and 435nm light and emit light into the 500s.

 

I wonder what would be the exposure difference for your flower if you illuminated with your Led, but placed a Lp 475nm filter on your camera, like a wratten #8. Then see if its the same glowy green.

 

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There is one Allamanda flower in the yard, I'll bring it in tomorrow night & give it a go.

I have a 410nm long pass I'll see what I have at 475nm long pass.

I did look at the flower a bit earlier & saw no fluorescence by eye.

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