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Anybody have some alabaster? WB in fluor photos?

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#41 Andrea B.

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Posted 05 March 2020 - 17:14

I became/am curious about the actual paper shown. It seems to be neutral in the UViVF photo.

But, yes, the gypsum is also interesting as related to alabaster. The gypsum doesn't seem to be completely neutral.

Added later: Or vice versa. See next.
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#42 Andy Perrin

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Posted 05 March 2020 - 17:20

View PostAndrea B., on 05 March 2020 - 17:14, said:

I became/am curious about the actual paper shown. It seems to be neutral in the UViVF photo.

But, yes, the gypsum is also interesting as related to alabaster. The gypsum doesn't seem to be completely neutral.
Doesn't that depend on which thing the white balance was done on? The gypsum could the the neutral one and the paper tinted?

#43 Andrea B.

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Posted 05 March 2020 - 17:32

Yes, of course.
My interest is this:
If we could measure by how much either the paper or the gypsum is "off" as compared to Spectralon, then maybe we could develop a useful white balance adjustment for everyone to use who cannot afford the UV Innovations fluorescence standard. When I was experimenting earlier with the UV Innovations targets, I tried to coorelate the WB results to one of the in-camera settings like Daylight or a K number, but neither could be used. Too far off.

The paper would probably be easier to use than gypsum powder or solutions.
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#44 Ninjin

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Posted 05 March 2020 - 17:33

View PostAndrea B., on 04 March 2020 - 19:57, said:

Am I understanding correctly that Canson watercolor paper is useful as both a UV-induced visible fluorescence standard as well as a reflected UV standard??

I can not say if this is useful as any standard.. May be.
I'm doing balance this way - for UVIVF, on this 'target' - paper.
It works pretty well for me, but I don’t have a 'professional target', so I can’t compare how well.

For reflected UV - PTFE this is the best target, of course. But these paper samples are very close, and can be used as a background: for photo of luminescence, for reflected UV, IR and IR luminescence. The background will be +_ the same everywhere.

Test UVIVF:
Left - RAW, right - white balance NX_D on paper No. 4.
If you see how this situation can be improved, please say..

Attached Image: 1uvlumwb.jpg

The big sheet and the round target - PTFE (thanks to Cadmium).
My paper samples:

1 - "For oil and acrylic" paper FABRIANO.
2 - Оrdinary Russian standard for watercolor.
3 - Сanson Arches France for watercolor.
4 - LANA "Aguarelle Grain fin".
5 - Canson (Grain).
6 - Canson Montval.

As a background for paints and for the target for balance - I use paper sample № 5 usually. The gypsum sample on the first test was also painted on paper № 5
Other samples of paper are slightly different, you can see on this test a few.
I think this watercolor paper is called - 'cotton cold pressing', but I do not know for sure.


Vis - reflected UV (S8612+U360):

Attached Image: 2visuvwb.jpg


Paper № 4: Vis->UV->UVIVF

Attached Image: 4.jpg

Edited by Ninjin, 05 March 2020 - 17:36.


#45 Andrea B.

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Posted 05 March 2020 - 17:41

P.S. I found a local source for that paper, so I'll give it a try. Why not? :grin:

Part of the problem with fluorescence targets is that so far the only existing ones are "tuned" to a particular peak wavelength (around 365 nm).

The good thing about reflective targets such as Spectralon and to a slightly lesser extent PTFE is that they are stable (or almost stable) across a very broad range of light. I'm thinking we won't be finding anything similar for UViVis fluor. But that's probably OK as most of us are using 365nm illumination for UViVF.
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#46 Andrea B.

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Posted 05 March 2020 - 17:43

Ninjin -- THANK YOU for posting this information. It is all very interesting and useful. Even if the paper is not the "perfect" target for white balance, it appears to be quite useful as a background. I will try to test some paper against Spectralon and post what I get.
If I can measure, in some way, the difference between Spectralon and some paper, this will be useful to all of us I hope.
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#47 colinbm

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Posted 06 March 2020 - 03:26

Question please...
Does Spectralon show white in UVIVF & Steve's PTFE shows as dark orange ?
Cheers Col

#48 Cadmium

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Posted 06 March 2020 - 05:08

Colin, I hope this helps answers those questions.
Here is my test using Canson Watercolor Paper, Spectralon (white 99%, gray 75%, and black 02%), PTFE 1mm thick, and WhiBal gray card.

UVIVF (with and without Jupiter Logic Uranium Marble), and Visual.
UVIVF shots were WB on paper. Visual was WB on SRS-99.
Attached Image: Canson_UVIVF_and_Visual.jpg

Reflected UV. White Balanced on SRS-99.
Attached Image: Canson_R_UV.jpg

Canson Warecolor Paper:
Attached Image: Canson_Watercolor_Paper.jpg

#49 colinbm

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Posted 06 March 2020 - 06:05

Thanks Steve.

#50 Ninjin

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Posted 06 March 2020 - 06:55

Andrea, thank you! I am very interested to see any the results for UVIVF balance.

#51 Ninjin

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Posted 06 March 2020 - 06:59

Cadmium, Thank you so much!! I am very happy to see your result. This is the first time I see a comparison with Spectralon.

I think - your UVIVF balance looks the same in color as in my test.
PTFE looks a little darker, - however, IF I turn up the brightness in your photo, I can see that the PTFE color is very close as in my test.
I suppose - the color is calibrated the same. Just a lighting difference, probably. I used 2 filtered convoys and very close.

Attached Image: 3visuvwb.jpg

Your reflected UV sample looks a more violet.
But may be a difference in paper. Have you tried balance on the PTFE?

I will try to find the packaging from the version that I used.
Thank you so much again, you really helped!

[upd]
These two. №5 and №4 in the paper test. It will be the most white.
Attached Image: 6.jpg

Edited by Ninjin, 06 March 2020 - 07:27.


#52 Cadmium

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Posted 06 March 2020 - 08:30

Evgeniya, I did try white balance on the PTFE 1mm, and it was very close to the Spectralon.
Do not worry that your results are different than mine. Such tests will have different results with everyone.
Your visual and reflected UV are very similar to mine. I am white balancing on the Spectralon, and my PTFE is a little bit dirty it seems, more than yours is maybe.
I was also using NX-D for all these I did here, like you.
My torches are filtered, other than that? I am using a D-610 stock with lens barrier for these, instead of the D7000 UVIR I used for the reflected UV shot.
I am using a group of 7 filtered Convoy that have the parabolic reflectors removed for no beam hot spot.
Such a group has no hot spot and doesn't require a long exposure. Powerful, soft, and no light painting required for these shots.

I don't know if my Canson paper is the same, but it was all they had that was water color type, and they had various sizes of that same Canson Watercolor Paper.
It is very nice paper, and very white in UVIVF.
The paper was the only white material to white balance with in the UVIVF photos.
I don't have the $800 target that Andrea has, I have ordered the UVIVF dive target however, just to try out. It is a very cute target.

And now what everyone has been waiting for: :tongue: (these little faces are really fun)

The Jet Propelled Monster Seven Nichia 365nm Whammer Jammer with SLC (Soft Light Conversion) and U-340 2mm filteration:
Visual:
Attached Image: Convoy_7_Visual_1080.jpg

UV-only using La La U:
Attached Image: Convoy_7_UV_1080.jpg

Edited by Cadmium, 06 March 2020 - 08:42.


#53 Ninjin

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Posted 06 March 2020 - 10:06

View PostCadmium, on 06 March 2020 - 08:30, said:

different

So your result is ✿ not different ✿ - that’s the point.

Your filtered light 365 nm comes from the convoy to Spectralon and is reflected almost 100%. The filter on the camera lens blocks 365, + no luminescence of Spectralon = Spectralon black. OK.

But PTFE is brown - so it is the color of luminescence. Right or I was wrong?
This means - that it does not reflect 100% in UV, part goes into luminescence and the color of the luminescence should be the same.
..If you have the same light, the same PTFE material, and the same material for determining white balance -
The color of any luminescence should be the same.
So this is important - that’s the whole point. There is a goal from the tests - set the balance for to determine the color of luminescence equally..

[upd] This cool device from convoys impresses immediately ;-)

[upd2] Although it seems to me Spectralon is also not completely black.
Could Spectralon have a very weak luminescence like PTFE? It can be very weak, like 1% or less, but I think it is.

Edited by Ninjin, 06 March 2020 - 11:14.


#54 colinbm

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Posted 06 March 2020 - 10:25

@ Ninjin
This video explains ' brown '.
Brown has troubled me since kindergarten & now it is all clear...
https://www.youtube....h?v=wh4aWZRtTwU

#55 Cadmium

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Posted 06 March 2020 - 16:54

Evgeniya, The White Spectralon (SRS-99) when shot in UVIVF is also ever so slightly brown. This can't be seen in these photos, but it can be seen with the eyes.
The White Spectralon is the exact same brown color as the PTFE 1mm, except much darker, almost black.
Compared side by side using 365nm UV, there is a faint color difference between Spectralon White and Spectralon Black, the black version has no faint brown color, it is totally black.
"Brown", as Colin has pointed out in the video, is really orange, very dark orange, which could be very dark orange/red I suppose also.
However, neither the White Spectralon or the PTFE 1mm is being used for white balance in the UVIVF shots, they can't be, they are no where near white,
so instead I am using your Canson Watercolor Paper, which you recommended, because it looks very white in UVIVF.
Again, I didn't know there was any other kind of Canson Watercolor Paper, I even asked the people in the store,
so I have no idea if the paper I have is different than what you have, but this paper I have seems to work rather well as a UVIVF white balance target.
Again, using my eyes, and that is what we try to duplicate when white balancing UVIVF, we usually would want the photo to accurately look the same as how it looked to our eyes,
the Canson Watercolor Paper looks very white to my eyes when illuminated with 365nm UV.
That pertains to Andrea's original question:
"Am I understanding correctly that Canson watercolor paper is useful as both a UV-induced visible fluorescence standard as well as a reflected UV standard??"
I would say that the Canson paper I have is definitely the best UVIVF white balance target I can think of, but I either sent Andrea my white fluorescence paint or I can't find it to compare,
but regardless, the Canson Watercolor Paper is very white in UVIVF.
I would say the paper is not exactly white in reflected UV. Here is a comparison, reflected UV (La La U), white balanced from RAW using PhotoNinja, using PTFE 1mm (left) and using Spectralon (right),
there is no real difference, but this does show some slight color in the paper.

Attached Image: Canson_Watercolor_Paper_LaLa_U_Ninja_PTFE_1mm_vs_Spectralon_1280.jpg

Edited by Cadmium, 06 March 2020 - 17:49.


#56 Andrea B.

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Posted 06 March 2020 - 18:40

Steve, you beat me to it! :lol:
Good experiment.
(No, you didn't send me any white fluorescent paint.)

**********
Could Spectralon have a very weak luminescence like PTFE? It can be very weak, like 1% or less, but I think it is.

Remember when using Spectralon that it is very easy for Spectralon to reflect another object's fluorescence**. (Spectralon itself is not fluorescent.) I had a problem with my Spectralon reflecting some fluorescence from white painted bricks in an experiment a couple of years ago.

**********
The Jet Propelled Monster Seven Nichia 365nm Whammer Jammer with SLC (Soft Light Conversion) and U-340 2mm filtration

AWESOME !! :cool: :cool: :cool:

**********
**Spectralon is a diffuse reflector. Any incident ray is scattered in multiple directions.
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#57 Andrea B.

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Posted 06 March 2020 - 18:44

I should remind everyone that white balance alone is not always sufficient to produce accurate colours. You also need a color profile for the camera which includes the lens, filters and illumination used.

Added: However, I cannot figure out how you would make a color profile for UViVF.
UViVF certainly does present interesting problems to solve with respect to white balancing.
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#58 DaveO

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Posted 06 March 2020 - 23:37

Just when you thought you knew all about Spectralon have a look at this

UV exposure of Spectralon
http://hep.ucsb.edu/...vcontampfte.pdf

Ho hum
Dave

#59 Cadmium

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Posted 07 March 2020 - 00:18

Andrea, Correct, I didn't send you the paint, I found it today, hiding. It is SO BRIGHT WHITE! I have not compared it to the paper in a photo yet.
I think I will wait until I get the dive card, so maybe tonight, or this weekend.

Good point about Spectralon reflecting, but the spectralon is not reflecting anything here, I have put the white and blak next to each other, and there is a tiny bit of brown detectable in the white compared to the black,
the black is definitely more black than the white, this doesn't show up initially, you have to compare them together. They both look black if you don't compare them.
However, this is not important in UVIVF, because we can't use spectralon for UVIVF anyway. The brow also shows up if you look very close at powdered PTFE also. I have no idea what the brown comes from.
I have a small can of powdered PTFE, it is black in UVIVF, but if you compare and look close you can see hints of brow. Nothing is as black as the Spectralon Black, it is really back, more than any other black.
Again, this doesn't matter in UVIVF, what does matter is how white the paper is. It looks very white to me, but what do we compare it to really? Just to everything else I guess, and visually it looks white to my eyes.
Would be good to compare it with your tester.
My dive card is probably not as good as your tester.

#60 Andy Perrin

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Posted 07 March 2020 - 04:19

View PostDaveO, on 06 March 2020 - 23:37, said:

Just when you thought you knew all about Spectralon have a look at this

UV exposure of Spectralon
http://hep.ucsb.edu/...vcontampfte.pdf

Ho hum
Dave
That article is from 1993...I wonder if the recipe for Spectralon has been revised since then to remove the impurity.