Ultraviolet
Ultraviolet (or UV) is the spectrum of wavelengths shorter than those of visible light.
They start at the end of the visible spectrum at around 400nm and extends down as far as 10nm. However, the atmosphere begins to block UV light from 315nm and is completely absorbed by 280nm.
Applications
Aside from a plethora of scientific uses, filming in ultraviolet presents some interesting creative opportunities for filmmakers.
Some insects and animals are capable of seeing into the UV spectrum. Emulating their vision can reveal striking patterns on plants that are otherwise invisible.
Viewing this spectrum is also useful in evaluating the effectiveness of protective products such as sunscreen or sunglasses – they will appear black if they’re working as they should.
Lastly, some people also think that ghosts and spirits can be seen in this invisible realm, though we’ve yet to see evidence ourselves…
Luminescence
Some things are only visible in UV. But sometimes things can react to ultraviolet light, absorbing and re-emitting it in the visible spectrum.
Fluorescence is when the object stops glowing once the UV source is no longer present. Surprisingly, there are loads of animals and even minerals that flouresce under UV light.
Phosphorescence is when it continues to glow after the UV source has gone out, re-emitting the light slowly over a period of time. Glow-in-the-dark stickers are a great example.
Also worth mentioning for clarity is bioluminescence. This is where an organism glows by its own chemical process and is not dependant on a source of UV.
In all three cases, as the emitted light is in the visible spectrum – no special equipment is needed to film or photograph, just the absence of other light such as in a dark room or at night.
Is it safe?
Despite our atmosphere blocking the most harmful UV rays, it’s still possible to get burnt by the sun.
In the same way, caution must be excised if using artifical UV light sources. Some of these output wavelengths which not only burn skin but can damage eyesight or even blind.
Appropriate eye protection needs to be worn when using artifical UV light sources.
FAQ
What is ultraviolet?
Ultraviolet is part of the electromagnetic spectrum beyond violet in the visible spectrum. It starts at around 400nm and, fading
What does ultraviolet look like?
Ultraviolet, as the name suggests, produces purply images. This will be stronger or weaker depending on your white balance, and in post-processing you’ll probably want to neutralise this colour cast, often resulting in a greyish tone with pops of different colours depending on the UV reflectivity of objects within your scene.
How do I film in ultraviolet?
If you simply want a fluorescent effect that’s often associated with ultraviolet, then any camera will work. You just need a UV light source (and preferrably some eye protection) and you’re good to go.
If you’re after the real UV spectrum however, you will need a camera system that is sensitive to ultraviolet light – and prepare yourself for underexposure. Even in direct sunlight or with artifical sources, ultraviolet light is scarce. You’ll need slower shutter speeds for photos and, for filmmaking in particular, expect to crank your ISO right up, even in broad daylight.