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UV fireworks during Canada's 150th birthday in Ottawa

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#1 Hornblende

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Posted 02 July 2017 - 04:57

Today was Canada's 150th birthday celebration in Ottawa (and the rest on the country of course).
It was a tough day, the weather was merciless, hot and humid with frequent rain, plus lots and lots and looots of people in the streets!
At the end of the day everybody thought the firework show would be canceled because of the weather. Fortunately rain stopped and the show happened!
I jumped at the opportunity to take pictures of the event in ultraviolet light. I was expecting the fireworks to generate a fair amount of UV light, I was not disapointed and I am happy with the result! I had to push the ISO very high tho, otherwise I would be stuck at 30+ seconds of exposure and the fireworks would be smoothed out.

Gear: Canon 6D full spectrum - El Nikkor 80mm f/5.6 - Baader U
25600 ISO - f/5.6 - 2 to 4 seconds of exposure - custom white balance on with PTFE in sunlight

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BONUS: near infrared (830nm)
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Edited by Hornblende, 02 July 2017 - 05:01.


#2 Andy Perrin

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Posted 02 July 2017 - 05:18

It's interesting that the light isn't (false) colored. You used sunshine for the white balance, which suggests that either the light was so bright it's simply saturating the sensor, or that the UV has a similar spectrum to sunshine. Perhaps all the UV is coming from black body radiation (incandescence) rather than the luminescent chemicals that normally color the fireworks?

Edited by Andy Perrin, 02 July 2017 - 05:20.


#3 Hornblende

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Posted 02 July 2017 - 05:34

Indeed, the light saturated the sensor
I don't think the fireworks are "hot" enough to generate a sunshine like spectrum, my guess would be the emission line of the chemical elements used for generating colors, but you could be right.
However, now that I think about it, since the Baader U leaks a bit of infrared light there is a possibility that my UV fireworks are in fact IR fireworks. I hope not :(
At 25600 ISO and several seconds of exposure, strong IR sources could leak through, right? There is 12-13 EV difference between my UV pictures and my IR picture of the fireworks. Do we know how much IR is the Baader-U able to block?

Edited by Hornblende, 02 July 2017 - 05:46.


#4 Andy Perrin

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Posted 02 July 2017 - 13:37

Yeah, they could be IR, and I think we've already had a long thread about that where we showed that under extreme conditions like this, it does leak IR. You should check the old thread.

If it were the emission lines of the usual coloring chemicals, the results would NOT be white. Emission lines are called "lines" for a reason.

Edited by Andy Perrin, 02 July 2017 - 13:39.


#5 Andrea B.

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Posted 02 July 2017 - 14:52

.

HAPPY BIRTHDAY, CANADA !!!!!


We love you guys!!
I hope both countries can live thru the current US Trumpeter era. Oh geez. Sorry for that little digression. It's a bit crazy here and I'm not used to it yet. If ever.

****************

I daresay you have at least some near-UV in there at least around the 400 range given your 12-13 EV difference. But is it the fireworks? Or is it from the other lights and that purple glowing orb thing?

We know the BU can pass some IR. But it's a tough call to decide without further experiment whether 2-4 seconds @ ISO-25600 will produce that leak and if so, how much when recording fireworks.

The false colours are subject to mis-interpretation. Setting was Daylight WB, but you were not shooting in Daylight. And if the fireworks light is blown, even slightly, false color gets lost anyway.

Now I have to go see what the fireworks chemicals are. :lol: :lol: :lol:

I think the 830nm IR photo is very nice !!!!!! B)

*******
SEE ALSO:
http://www.ultraviol...y-of-fireworks/
Andrea G. Blum
Often found hanging out with flowers & bees.

#6 Andrea B.

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Posted 02 July 2017 - 15:34

Magnesium is used in fireworks. Magnesium combustion releases UV and Visible light.
Example: Sparklers
Sparklers are cheap and easy to find (around certain holidays), so would be a good test subject for fireworks UV photography to test filters.

I can find scads of material on visible emission spectra for elements. But cannot find any charts or tables for the UV range. Gotta be out there somewhere.
Andrea G. Blum
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#7 OlDoinyo

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Posted 03 July 2017 - 02:28

Good to see someone revisit this topic. The chromaticity is indeed very limited in the UV, as many of the coloring agents have few if any UV emission lines. The Mg emission is basically incandescent.

#8 enricosavazzi

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Posted 04 July 2017 - 09:19

View PostAndrea B., on 02 July 2017 - 15:34, said:

(...) I can find scads of material on visible emission spectra for elements. But cannot find any charts or tables for the UV range. Gotta be out there somewhere.
The NIST has data on the strongest emission lines of elements, including Vacuum UV, UV, VIS and NIR.

Select the element at http://physics.nist....lement_name.htm , then the Strong Lines button (or the Persistent Lines buttons for ionized or non-ionized states)
-- Enrico Savazzi

#9 Andrea B.

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Posted 05 July 2017 - 01:47

Enrico - thank you so much!! That is exactly what I was looking for.
Andrea G. Blum
Often found hanging out with flowers & bees.