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Request: Please read UVIVF Sticky


Andrea B.

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https://www.ultravioletphotography.com/content/index.php/topic/1247-nichia-033a-uv-led-shiny-metal-test-for-visible-output/page__view__findpost__p__7184

 

In 2015 when I showed this example of visible light leak from a Nichia UV-LED torch, I did not show the photos in its raw colors. I'm going to go try to find them and look at them in Raw Digger. If this view is enlightening (pun??), then I'll post one into the UVIVF Sticky.

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If I didn't miss any, I clicked on every link, and they all open. Some pages open with a lock (the emoji is not supported it seems), others with a ⚠️ (I am on a smartphone).
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If I didn't miss any, I clicked on every link, and they all open. Some pages open with a ������, others with a ⚠️ (I am on a smartphone).

 

Ops, double post.

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Great article, Andrea. Very useful to me as I'm just starting down the fluorescence path for my winter project (where darkness is an advantage). Here are my comments.

 

1) I'm reluctant to put another task on your shoulders, but how about extending the article to include UVIIRF and VIIRF? There's far less info. around about these than there already is for UVIIF.

 

2) Perhaps add something about using bandpass filters over the lighting source to get diferent output colours.

 

3) UV-LED Flashlight (aka Torch) - suggest updting this to refer to newer torches which UVP members like, such as Convoy and Nemo.

 

4) "Flash It is possible to induce visible fluorescence with UV-flash. However, if the fluorescence is dim, then a longer exposure under a steady UV-lamp or UV-LED torch may be necessary." - another approach is to leave the shutter open and use multiple flashes (as ell as multiple flashguns).

 

5) I agree that WB is a real issue so I was interested to read your comments. But $875 for a UV Gray card rules it our for most of us. We need another standard. You indicate that using the camera's Daylight WB has drawbacks, but it may be the only pragmatic approach for most people.

 

But that only works for UVIVF, not UVIIRF or VIIRF. In the absence of anything else, I am using the one and only rock I have in the house (a cut and polished rock intended for use as book-ends, bought in the US on my first trip there some 40 years ago!) which fluoresces white in UVIVF and seems to flouresce across the NIR range under both UV and visible excitation (which I can tell from my tri-colour exposures).

 

So perhaps a specific type of rock might make a good WB standard?

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UVIIF is a mis-type for either UVIIRF or UVIVF ! I seem to have developed a serious habit of missing keys when I'm typing.

 

In the penultimate para. above, UVIIF should have been UVIVF - I've edited it.

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Colin - if you find your rock and it does the job, let me know. We could at least have a standard for the two of us! (I remember many years ago when standards were a hot topic in computing there was the saying "The great thing about standards is that there is one for everyone.")
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.

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Damon, thank you for the linkie check.


 

Bernard, thank you for your comments. Very useful.

 

(1)....how about extending the article to include UVI-IRF and VI-IRF

As always, any member here is welcome to write up an article about any topic. Birna and I will read it over and approve it for a Sticky. For example, I ask Andy to write about SWIR. Keep any article simple and informative. Link to examples posted on the forum.

 

(2)....bandpass filters

Thought I had something about bandpass, but will amend as needed.

 

(3)...refer to newer torches which UVP members like, such as Convoy and Nemo

Yes.

 

(4)...flash...another approach is to leave the shutter open and use multiple flashes

Would like to see an example. Repeated flash tends to blow out areas, but if the flash is dialed down and repeated, then it could be useful.

 

(5)....$875...UV Gray card. We need another standard. You indicate that using the camera's Daylight WB has drawbacks, but it may be the only pragmatic approach for most people.

We certainly do need an inexpensive standard for UVI-VisF !! This has been discussed more than once. So far nothing has been found to be useful.

My own experiments suggest also trying the lowest value K setting on your camera.

 

So perhaps a specific type of rock might make a good WB standard?

Does your rock happen to be alabaster? This has been suggested as a white fluorescing standard. I haven't seen any experiments about it yet. Remind me if it is in any of your posted photos, please.

 

White balance for UVI-IR fluor.

Emitted infrared light is recorded as a "false color". So white balance, per se, is not defined. Can IR fluor be standardized similarly to how we standardize our reflected UV photos for the botanical section? Perhaps, but I'm not sure just how.

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(4)...flash...another approach is to leave the shutter open and use multiple flashes

Would like to see an example. Repeated flash tends to blow out areas, but if the flash is dialed down and repeated, then it could be useful.

 

So perhaps a specific type of rock might make a good WB standard?

Does your rock happen to be alabaster? This has been suggested as a white fluorescing standard. I haven't seen any experiments about it yet. Remind me if it is in any of your posted photos, please.

 

White balance for UVI-IR fluor.

Emitted infrared light is recorded as a "false color". So white balance, per se, is not defined. Can IR fluor be standardized similarly to how we standardize our reflected UV photos for the botanical section? Perhaps, but I'm not sure just how.

 

Re. the flash, multiple flash is only used if the single-flash image is too weak, so blow out shouldn't be a problem.

 

Re. the rock, my knowledge of rocks is at the same level as my knowledge of botany. So I don't know what the rock is. But images provided below.

 

Re. WB for UVIIRF - yes, I agree that this is false colour so you can't define a "correct" WB. But as you say, standardisation is the objective.

 

Now, here is the stone:

 

Visible image. The area around the concavity near the centre is what I'm trying to use as a white standard. But the colouring does vary, which means I am still getting variations between UVIVF, UVIIRF, and UVIIRF depending on exactly where on the rock I've set the WB point - but an evenly-coloured rock should overcome this:

 

post-245-0-29352300-1607027045.jpg

 

UVIVF - this was an early experimental shot and I can't remember what WB setting I used. The EXIF says "Manual" - it may have been against fluorescing white paper, which I subsequently discovered has no red in it!

 

post-245-0-67457800-1607027178.jpg

 

UVIIRF merged tri-colour image (exposures made at 750, 850, 1000 nm) - this has been WBed to make the central section white.

 

post-245-0-88915600-1607027330.jpg

 

VIIRF (comment as for UVIIRF):

 

post-245-0-00137200-1607027365.jpg

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Andrea, the so called Nemo is made by WANFIRE.

https://www.ebay.com...ecAAOSwQ3le6EV-

Even if the "Nemo" is quite powerful the data in the eBay-link above is exaggerated and not really true.

For the facts, look at earlier posts. The main data is found here:

https://www.ultravioletphotography.com/content/index.php/topic/4051-convoy-s2-has-a-challenger/page__view__findpost__p__37933

 

Search for Nemo for other findings.

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Bernard, this rock appears to be Agate.

 

 

I think you're right, Colin. Apparently Agate is composed mainly of Chalcedony and Quartz. I have separate samples of both, and both show some fluorescence.

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What ever Nemo is, its the best we have for our $$$ & its brand name is 'WANFIRE', that is what I was bringing Andrea's attention to.

I fully agree with you. All you say is true, Colin.

Thank you for pointing out the brand name. that was new for me too.

 

The product specification from the seller is just a bit exaggerated. I wanted people to know that the numbers given are not exactly true even if the torch still is very good.

I have bought five of them for me so far and like them very much.

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