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Infrared, ultraviolet, and full spectrum: the basics

A plain-language intro to where infrared and ultraviolet sit on the light spectrum, how they differ, and what full spectrum means.

Updated

New to all of this? Here is the short version of what infrared and ultraviolet photography are, and how they relate to ordinary photos.

shorter wavelength · higher energy longer wavelength · lower energy Ultraviolet Visible Infrared ~10 nm 400 nm 700 nm ~1 mm UV photography Normal photography Infrared photography Full spectrum = ultraviolet + visible + infrared Illustrative, not to scale
Where each kind of photography sits on the spectrum.

What is photography?

Photography is a way of capturing images, and these days it is usually done digitally. Most photographs record the world the way our eyes see it, using the band of light we call visible light.

What is infrared (IR) photography?

Infrared photography records light from the infrared band, which sits just past the red end of what our eyes can see. That light is around us all the time. We just cannot see it, but a camera set up for infrared can.

What is ultraviolet (UV) photography?

Ultraviolet photography records light from the ultraviolet band, which sits just past the violet end of visible light. That puts it on the opposite side of the visible range from infrared.

What is the difference between IR and UV?

They sit on opposite sides of the visible band. Infrared has the longer wavelengths, just beyond red, and carries less energy. Ultraviolet has the shorter wavelengths, just beyond violet, and carries more energy. (Ultraviolet is the part of sunlight behind sunburn.)

There is a practical upshot for photographers. Because infrared’s longer wavelengths scatter less in air, infrared tends to cut through haze and hold up over distance. Ultraviolet’s shorter wavelengths scatter and get absorbed more easily, so they do not carry as far through the atmosphere.

What is full spectrum?

Full spectrum means all of it at once: ultraviolet, visible, and infrared. A full-spectrum camera has had the filter that normally blocks UV and IR taken out, so the sensor can record the whole range. From there you choose what to capture by putting a specific filter in front of the lens.

Want more on shooting infrared specifically? See What is infrared photography?. When you are ready to pick a filter, head to the filter reference.