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UVB 309nm in Various Fluorescence


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Up-graded the UVB 309nm LED light to 12 LEDs with 40 watts of power. With a second one to finish tomorrow.

Following is a variety of photos of various UVB 309nm induced fluorescence.

 

First is a picture of the new set-up with U325c filter glass.

 

post-31-0-33991300-1626269491.jpg

 

 

Second is Three Rocks in Visible Light.

 

post-31-0-49057500-1626269524.jpg

 

 

Third is Three Rocks in UVB 309nm Induced Visible Fluorescence.

 

post-31-0-66653600-1626269606.jpg

 

 

Fourth is Three Rocks in UVB 309nm Induced 410nm to 1000nm Fluorescence.

 

post-31-0-97672000-1626269679.jpg

 

 

Fifth is Three Rocks in UVB 309nm Induced UVA (Baader U filter on Camera) Fluorescence.

 

post-31-0-31039900-1626269705.jpg

 

 

Sixth is Three Rocks in UVA 365nm Induced Visible Fluorescence.

 

post-31-0-93943100-1626269734.jpg

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40 Watts of power, that a powerful UVB LED lamp!

 

The middle rock (blue in visible light) seems to change a lot between UVA and UVB. The rock on the right looks almost the same.

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Hi Col, I did some fluorescence of Yooperlite changing the wavelength of UV I used and looking at how the visible fluorescence changed. For the middle rock especially, I got a similar effect to you - redder and darker at 310nm vs longer wavelength UVA.

 

The thread is here - https://www.ultravioletphotography.com/content/index.php/topic/4087-yooperlites-specimen-uvf/page__view__findpost__p__39656

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Thanks Jonathan

The middle blue rock I know, it is Sodalite.

Yes Yooperite, looks nice, I haven't seen one yet.

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You might actually have some UVBiUVAF (uvb induced UVA fluorescence) in that middle rock.

That will be a first here.

Very cool.

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Thanks Toni & Thanks to Dave for suggesting the UVB I UVA Fluor.

It will be interesting to see how this develops & finding other reactions in this region.

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I am looking for a filter that cuts off before the BaaderU say 320nm & transmits below 300nm, that is passes UVB & below.
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The transmission in the PDF seems a bit too optimistic.

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Andy Perrin

The transmission in the PDF seems a bit too optimistic.

Don't know why you'd say that, it compares pretty closely to what Jonathan measured.

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Yes Jonathan's 55% transmission is insignificantly different than the pdf 60% transmission.

 

Even if the real transmission was 40%, you still couldn't really tell the difference on a camera for one that would be 60%.

1 stop difference would be 30%, 2 stops is then down to 15%.

 

So if the tested filter was 60% transmission at 1 second. Than a 30% transmission one would need 2 seconds exposure. At 50 to 55%, your less than a 1/3 stop and your exposure would be more impacted by the distance of your light source or the angle of the sun light.

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I think a lot of those would look a lot better with some white balancing. Might make them less scientifically accurate but at least everything won't be swamped in blue.
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Don't know why you'd say that, it compares pretty closely to what Jonathan measured.

Well I said that because that would imply the filter doesn't leak at all

 

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Andy Perrin

Well I said that because that would imply the filter doesn't leak at all

 

Nope, it does not imply that. The problem is that the scale in both Jonathan's graph and the PDF's graph are linear scales, but our cameras and eyes are logarithmic. On a linear scale, you can NEVER read the OD of blocking for out of spectrum stuff. It's just too small to be visible unless the leakage is huge. This is why we use log or diabatic graphs when we want to show that information. The graph in the PDF is not misleading provided you understand that linear graphs all have this limitation.

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Also seeing UVB in sunlight, as Jonathan said, is not easy. OD 4 isn’t enough.

 

With the above I mean that even if you have a good blocking (like OD 4), a filter may still leak.

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Nope, it does not imply that. The problem is that the scale in both Jonathan's graph and the PDF's graph are linear scales, but our cameras and eyes are logarithmic. On a linear scale, you can NEVER read the OD of blocking for out of spectrum stuff. It's just too small to be visible unless the leakage is huge. This is why we use log or diabatic graphs when we want to show that information. The graph in the PDF is not misleading provided you understand that linear graphs all have this limitation.

Oh, I see, thanks for explaining.

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I think Yooperlite and sodalite are the same thing.

 

There seems to be more light in these frames than mere fluorescence from the rocks. It appears that ambient light might be reflected.

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Ok, Invisible Vision 308nm. Yes, I have one. Yes, I'm glad I bought one. Do I use it every day, no. My transmission data is similar to the manufacturer data and well above their minimum peak transmission quoted on the spec sheet (40%).

 

All filters leak. Whether it is an issue depends on how you use them and your application. In bright sunlight, using a camera with the Bayer filter still present on the sensor, I got evidence of leakage of IR with that filter. The with 'Bayer filter on the sensor' is important, as we know that the Bayer filter blocks a lot of light in that 300-320nm region. This will accentuate the effects of any leaks at longer wavelengths. Would this be different with a monochrome camera conversion? Probably, as that would have greater UV sensitivity in that region, while not having much change to IR sensitivity.

 

If I were to use this filter indoors in the dark, with a 302nm UVP lamp which has some small peaks at other wavelengths, would this 'leak' be a problem? Probably not. But if I were to do that, I would test for leaks and see if it is a problem as I do with any new combination of camera, lens, filter and light.

 

One other thing to mention, Invisible Vision make and sell equipment for some pretty specialised imaging applications. That filter is not really aimed at people like us sticking them on what is in effect a normal camera and trying to take pictures in sunlight. As such it is being used in a way the manufacturer didn't design for when we do that with it, and we should take that into consideration when looking at the results from it.

 

Spec sheets and numbers are one thing. Real world experience with a filter is another.

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Thanks Jonathan

At this stage I intend to use the UVB 309nm LEDs for UVA & Visible fluorescence, with my 'full spectrum' converted Sigma fp.

I am very tempted to make a mini 'dust free' lab to remove the sensors' cover glass & replace it with fused silica, to hopefully improve the UVA reach.

Then if that is successful, then getting a Sigma fp converted to full spectrum mono.

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Just to run it past here...I also have some UVC lights for, UVC I Vis Fluor, Is it possible to do, UVC I UVA Fluor ?
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Just to run it past here...I also have some UVC lights for, UVC I Vis Fluor, Is it possible to do, UVC I UVA Fluor ?

 

Much harder. As your UVC light is Mercury right?

If it was an LED with narrow band , than maybe. But a Mercury bulb, even the germacidal low pressure ones give off all the Mercury lines. So from your bulb you will get too much contaminated 365nm line.

 

Unless you buy an even more expensive narrow 254bp filter to place on the Mercury bulb.

 

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Hi Dave.

Yes I have Mercury UVC, but I have been making some UVC LEDs to try out too.

I have 265nm & 275nm UVC LEDs sets as well now.

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