Do the invisible inks/dyes that show up under blacklights show up in UV photographs?

[LiveWild]

Simply put do  UV cameras, or cameras that operate with only UV light, pick up dyes that are florescent even with out a black light to expose them? The dyes I'm talking about are common with 'invisible inks'( google image search for reference), but are also used for tattoos (reference), and even some hair dyes (reference). 

 

The best example of what I hope to achieve is this Wikipedia photo that shows two photographs of a man with sunscreen one normal the other UV. As anyone tried something similar but with those kinds of invisible inks mentioned above?

[colinbm]

Two different techniques are involved here.
For the fluorescent dyes, you need a UV light of 365nm to light up the dye, you only need a normal visible light camera to take the photos.
For photographing the sunscreen on a human, you need a camera that can 'see' in the near UVA sunlight.
Some normal unconverted cameras can still see this UVA light with a Badder U filter on the lens to block out the visible & near IR light.
 

[OlDoinyo]

If the ink is excited by near- UV, then it will appear dark in a reflected UVA photograph even if it is colorless in visible light. If the excitation is in UVB or UVC then this may not be true.

[colinbm]

9 minutes ago, OlDoinyo said:

If the ink is excited by near- UV, then it will appear dark in a reflected UVA photograph even if it is colorless in visible light. If the excitation is in UVB or UVC then this may not be true.

This is very dangerous, Do not expose humans or any living creature to UVB or C !

[Andy Perrin]

Colin, I don’t think he said anything about exposing humans to UV-B or -C. Just ink on paper presumably. 
 

Probably we should try the experiment (in UV-A) and see if the ink shows up. 

[Fandyus]

11 hours ago, colinbm said:

This is very dangerous, Do not expose humans or any living creature to UVB or C !

No living creature should be exposed to UVB? Have you heard about mammals making vitamin D from the sun?

Edit: Or, like, UVB lamps for reptiles? To keep them healthy?

[colinbm]

35 minutes ago, Fandyus said:

No living creature should be exposed to UVB? Have you heard about mammals making vitamin D from the sun?

Edit: Or, like, UVB lamps for reptiles? To keep them healthy?

@Fandyus, please don't mis-quote me !
There is no UVB in Sunlight or very minimal, depending or the definition that you use !
It is what causes Sunburn. The UV lights that we use are many times more powerful then what the Sun gets through our atmosphere.
Do you have reptilian skin ? Then don't shine it on yourself !
I challenge you to measure 310nm from Sunlight from your location, but not on top of a high mountain.
Here is one definition, some are longer & some are shorter.......from Wiki
 

PS, those Reptile light boxes tell lies too.

[Fandyus]

@colinbmSorry if it seemed like I was misquoting you. It just felt to me like it was a little too final of a statement. I am quite sure that (upper) UVB can have certain benefits for certain living creatures sometimes, even if it's a force to be reckoned with.

Although, looking at your chart, I get why you would say this. But there is quite a lot of confusion about where what part of the UV spectrum begins and ends, and I have seen "UVB" be connected to vitamin D production in mammals many times. I am not actually sure what precise range of wavelengths helps with this or if it is "UVB" according to your chart.

[Lou Jost]

Wavelengths most effective for generating Vitamin D in mammals:

 

https://www.pnas.org/doi/10.1073/pnas.2015867118

 

This article contains a long discussion of risks/benefits of UV-B exposure to humans and describes UV-B irradiation experiments on human subjects. One point they make is that UV-B is several orders of magnitude more damaging than UV-A, but UV-B is much more effective than UV-A for vitamin D synthesis.

 

Another article shows that UV-A plays only a minor role in Vitamin D production, showing that exposure to UV-B is not merely optimal but actually necessary for adequate Vitamin D production, if a person is not outside for very long periods:

 

https://www.nature.com/articles/s41598-017-11362-2

 

Safety is not discussed much in the latter article.

 

 

 

 

 

[lukaszgryglicki]

Hey, in this forum sometimes there are too many (IMHO really) warnings about something (UV-B) that u'r exposed to almost every day. And this is end-of-disussion - I don't want flame wars - I just see too much of this. I'm very well OK playing with UV-C and don't see any reason for .... whatever. Ignore me.

[colinbm]

@lukaszgryglicki
Ignoring warnings that are universal is very foolish.
You are a loose cannon !

[Andy Perrin]

Lukas, people get skin cancers nearly everyday as well. The warnings aren’t needless, especially if people decide to play with more intense sources of UV-B than sunlight. 

[Foxfire]

With the main topic - a bit more broadly, as i've observed with flowers and other things, UViF may give a hint what will appear in reflected UV images, but sometimes also not - you may get a surprise. 
Here are two UViF-Vis-UVR comparisons: a sunflower and a maple leaf with black spots (caused by fungus Rhytisma acerinum). Based on UViF image, with the sunflower it can be kind of guessed what will appear in UVR, but with the maple leaf the UVR is surprisingly featureless, spots disappeared.  So, it seems to depend on some factors. Maybe if the color is coated with something, it does not appear in UVR, cause UV does not penetrate deeply.

 

 

 

 

[LiveWild]

On 10/2/2023 at 1:59 AM, Foxfire said:

With the main topic - a bit more broadly, as i've observed with flowers and other things, UViF may give a hint what will appear in reflected UV images, but sometimes also not - you may get a surprise. 
Here are two UViF-Vis-UVR comparisons: a sunflower and a maple leaf with black spots (caused by fungus Rhytisma acerinum). Based on UViF image, with the sunflower it can be kind of guessed what will appear in UVR, but with the maple leaf the UVR is surprisingly featureless, spots disappeared.  So, it seems to depend on some factors. Maybe if the color is coated with something, it does not appear in UVR, cause UV does not penetrate deeply.

 

 

 

 

 

This is kinda what I was looking for. The lack of black spots on the leaf is what I find concerning. Any recommendations for testing this method's viability with out breaking bank?

[Andy Perrin]

The thing is, I'm not sure there is any direct relationship here between what appears in fluorescence and what appears in UVR — it may be just that the same chemical that makes the dark part of the UV bullseye also has a UVIVF response (if it's an absorptive mechanism). But other chemicals may not have that UVR response but still fluoresce.

[Andrea B.]

Any area which absorbs UV light to produce an emitted visible fluorescence is going to appear dark under a UV-only filter. This is inherent in the very definition of UV-induced visible fluorescence. But using visible fluorescence as a "predictor" of what you might see in a reflected UV photo? No, you can't always do that because the relationship is not 1-to-1. That is to say, visible fluorescence implies a dark UV-absorbing area, but a dark UV-absorbing area does not necessarily imply fluorescence. This is happening in the sunflower photo.

 

There is some correlation between the sunflower fluorescence and the UV-absorbing bulls-eye. But It is quite obvious that not all areas of the sunflower's UV-absorbing bulls-eye region emit fluorescence. And it is also important to note that the areas which do fluoresce, do not do so at the same intensity (or color, either). For example, the sunflower pollen fluoresces more brightly than the fluorescent areas of the petals closest to the disk. To complicate matters, any emitted visible fluorescence also produces reflected light - possibly reflected by non-fluorescent areas of the flower. 

 

As for the leaf, both the leaf and its fungus absorb UV-light to produce red fluorescence. So the UV-only view of the leaf will not (cannot) distinctly show the fungus spots. The fungus spots absorb more visible light than the leaf does, so the spots appear dark in the Visible-only view.