Light sources under infrared

Which lights pour out infrared and which emit almost none. Why an IR shot that works in sunlight can fail indoors under LEDs.

Infrared photography lives or dies by your light source. Some everyday lights pour out infrared, others emit almost none, which is why an IR shot that works beautifully outdoors can fall apart indoors.

Relative near-IR output. Thermal sources (top) are IR-rich; fluorescent and LED are not. Illustrative, not measured.

Sunlight: the main source

Sunlight carries roughly as much infrared as visible light, so it is the easiest and strongest source for IR work. Overcast softens it but does not switch it off. You still get usable infrared on a cloudy day, just less of it (Kolari, LifePixel).

Incandescent, tungsten, and halogen

Anything hot radiates a broad spread of light that reaches well into the infrared, so hot-filament bulbs glow brightly in IR. That makes ordinary incandescent and halogen lamps excellent for shooting infrared indoors (RIT).

Xenon flash

A xenon flash, whether a small speedlight or a studio strobe, puts out a lot of near-infrared, sometimes as much as its visible output. That makes it one of the best IR sources after the sun. To shoot pure infrared with flash you still put an IR-pass filter on the lens to drop the visible light, and note that some consumer flashes have coatings that cut UV and IR (RIT, Kolari).

LED and fluorescent: the indoor problem

Modern white LEDs make light with a blue chip and a phosphor coating rather than by getting hot, so they emit essentially no usable infrared (a tiny tail at most). Fluorescent tubes and CFLs are similar: a faint, spiky spectrum with almost no IR. Under either one, an infrared photo comes out very dim and hard to white-balance (IES, Kolari).

The upshot

For infrared, reach for sunlight, incandescent or halogen, or flash. LED and fluorescent lighting will leave you underexposed. The dividing line is simple: sources that make light by being hot are IR-rich, sources that use a phosphor are not.

A fun one: infrared you can almost see

A common demonstration: point a TV remote at your phone’s camera and press a button. The remote’s infrared LED is invisible to your eye, but it often shows up as a faint white or purple glow on the screen, because phone cameras only partly block infrared. It is a quick way to prove there is light around you that your eyes cannot see.

New to the spectrum? See the basics. To pick a filter, see the filter reference.