Ink or paint that can only be seen by......

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vaguestleek

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Fernando
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Hello,

I am in need of a ink or paint that can only be seen by a camera flash. Or maybe LEDs that can only be seen once there has been a flash. Basically anything that is invisible to the human eye and appear visible on a image once a flash has been applied.

I have been searching for hours and haven't found anything, yet ;/

Thank you,

F
 
I'm not aware that there is such a thing. Flash is just white light... albeit very brief in duration, but white light nonetheless - it has no special properties and therefore anything that shows up under flash woudl just as easily show up under any white light source.


The closest you'll get is something highly reflective that you could aim a flashgun at... similar to the reflective material seen on car number plates etc. That would react to a directional burst of light on the same axis as the camera lens, but it wouldn't be invisible under normal conditions... it just wouldn't be reflecting back at the camera.


If you want something to only show under special lighting, you're better off with fluorescent material and black light. A paste made from washing powder and water reacts well under black light, but dries invisible under white light. You can also get security marker pens that are invisible under white light, but fluoresce brightly under black light.
 
It depends on the circumstances where you'll be using it, the material you want to apply the effect to and whether you're on with the effect being visible to the naked eye after the flash has gone off. You'll need to explain a bit more about what you're doing.

In a dark environment there are phosphorescing materials that will emit light as a result of the flash exciting them. I'm not sure if the effect is visible on the flash, but it's certainly visible to the naked eye afterwards. I've seen this effect triggered by a flashgun with 70 year old phosphorescent paint in an old air raid shelter (when originally applied this would have been an effective emergency light if the power failed).

A high visibility reflective material under a light cotton fabric would probably reflect strongly under a flash but not be noticeable in the absence of another strong light source.
 
Try working in the non-visible ends of the spectrum. There are paints, etc with UV traces or IR traces in them. Then use a flash or strobe light which is UV or IR (depending on your paint!), and grab image with a camera. You could apply filters to the camera lens to only see the target wavelength.

Be aware that camera sensors are often less sensitive in the non-visible part of the spectrum, and some camera sensors have IR blocking filters on the sensor.

I work in industrial machine vision, and we regularly use IR light sources and apply an IR pass filter to the camera so we can work covertly if required, and it means that we are not affected by changes in ambient lighting.

I hope that helps, but as you will be aware from domestic solutions here and into the world of commercial imaging, don't expect anything cheap!!!
 
there are colours that are almost invisible to the naked eye when against a white background. A light yellow on a white background is very difficult to see in small amounts , though a blue light improves its visibility. This simple trick is utilised here.
 
Looks like they managed to achieve what you are proposing with this campaign:

http://www.mirror.co.uk/news/technology-science/technology/your-child-eye-cancer-use-4774686

"When you take a photo of the poster using the flash, reflective particles embedded in ink printed on the pupil mean that it appears bright white instead of black." - not sure of the exact details but it sounds like something bespoke rather than something widely available. Maybe worth investigating further...
 
what do you want it for?
You can get UV active inks/ paints or reflective film.
I know someone that made number plates using reflective white, reflective black and IR blocking film (very slight pink but otherwise clear). When a gatso flashed it just showed white and no numbers. When hit by a IR light from the ANPR systems it came back black. No one ever spotted the non standard nature.
 
Fluorescence is distinctly different to luminescence but you can purchase luminous paint and markers which react to flashlights or a bright light. It's worth searching on eBay etc.
 
There is a technological solution, but it's not cheap. You need a powerful image projector with a very fast light switch rate (such as a powerful flashgun) which is activated very briefly by a camera flash. So you can for example project words onto the side of building, and with a short flash duration nobody will see them, and nobody will be able to photograph them, except someone using flash.
 
chris malcolm said:
There is a technological solution, but it's not cheap.
Click to expand...
When you say there *is* a technical solution, are you implying that this device (1) exists, and (2) works as described? It sounds somewhat far-fetched to me, but I'm more than happy to be proved wrong.
 
StewartR said:
When you say there *is* a technical solution, are you implying that this device (1) exists, and (2) works as described? It sounds somewhat far-fetched to me, but I'm more than happy to be proved wrong.
Click to expand...

No it will work, its the old 'subliminal message' technique. There are countless old TV broadcasts (not necessarily in the UK) that had a single frame of something else inserted in the pre-title or title sequence, that were missed by 'normal' viewers, but if you played the material frame by frame you would see it.
 
The cynic in me can't help thinking that the OP will reappear (he hasn't been here since his first and only post) with a solution to the question.

The helpful chap that hides behind the cynic tells me that something reflective worn behind something slightly sheer will show on photos taken with flash but be pretty much invisible under normal lighting conditions (in the same way that some celebs are "(?)accidentally" snapped with their underwear showing under their evening attire.)
 
Mr Perceptive said:
No it will work, its the old 'subliminal message' technique.
Click to expand...
Yes, I understand that. It's the technology I don't believe. A projector that can project an image bright enough to be photographed using a flash? How many watts is that then?
 
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