Introduction to Infrared Photography

The short answer: infrared photography records light just beyond the red end of the visible spectrum. Digital sensors can see that light, but every camera has a hot mirror filter in front of the sensor that blocks it. To capture infrared, you either put an infrared filter on the lens of an ordinary camera and use long exposures, or you have the camera converted by replacing the hot mirror. Foliage reflects infrared strongly, which is why leaves turn white. After a color swap in editing, the sky turns blue.

I was invited to present to the Santa Clara Camera Club on the subject of Infrared Photography. This was a great opportunity to share some of the topics that I’ve been working on in a new format. Thanks to Tim Cuneo, Luke Lang, and all of the members of the Santa Clara Camera Club for their hospitality.

I streamed the presentation to YouTube. The recording is below. For my first stream, it went off relatively well. Unfortunately, I didn’t capture the Zoom meeting audio in the stream/recording. This missed the introduction for the first 3 and a half minutes and the great participant questions. Feel free to skip the first 3 and half minutes of me staring ahead and saying nothing. 🙄 I did try to repeat most of the audience questions in the answers, so hopefully, you should have enough context.

You can view the presentation deck with my notes.

What Is Infrared Light?

Visible light has wavelengths from about 400 nm to 750 nm. Digital sensors capture a wider range, from about 350 nm to 1000 nm, which includes some near ultraviolet and near infrared. A hot mirror filter in front of the sensor blocks that extra IR so normal photos look normal.

There are three ways to capture infrared:

1. Infrared film, which is sensitive to both visible and infrared light.
2. An infrared filter on an unconverted digital camera. The filter blocks most visible light, which lets more infrared through than the hot mirror would otherwise allow.
3. A converted camera, with the hot mirror replaced by an infrared filter, an ultraviolet filter, or clear glass for full spectrum.

Styles of Infrared Photography

• Traditional infrared uses a 720 nm filter. It passes a small slice of red plus infrared. Foliage turns white, and a color swap in editing gives a blue sky.
• Black and white infrared can be shot with a range of filters, either as a monochrome JPEG or as a raw file converted in editing.
• Deep infrared uses a filter at 800 nm or higher and records infrared only. It’s usually converted to black and white, with inky black skies and water and white foliage.
• Color infrared uses filters from about 470 nm to 665 nm and keeps some visible light. After a color swap, skies are blue or teal and foliage is yellow or orange. Most of my color infrared is shot at 590 nm. It requires a converted camera.
• Full spectrum uses a converted camera with clear glass. Images have a red or violet cast, and lens filters let you shoot any other style.
• Chrome mimics Kodak Aerochrome film, which was discontinued in 2009. A dual band filter gives red or pink foliage with less editing. It requires a converted camera.
• Ultraviolet needs a full spectrum camera and a UV pass filter. It isn’t infrared, but it uses the same equipment and techniques.

Unconverted or Converted?

An unconverted camera is the easiest and most affordable way to start. You probably own everything except the filter. It covers traditional, deep, and black and white infrared. Use a quality 720 nm filter, such as the Hoya R72, Kolari Vision standard IR, LifePixel standard IR, or Tiffen #87. Long exposures show the flaws of cheaper filters. Expect 5 to 30 seconds at 720 nm in daylight, and several minutes for deep infrared at 800 nm or more. You need a tripod and a remote or self timer, and moving subjects will blur.

A converted camera opens up every style and shoots at normal shutter speeds, so you can work handheld. You can add external filters with a higher cutoff than the conversion. My 590 nm camera also shoots 720 nm, 850 nm, and black and white with lens filters. The tradeoffs are cost, a voided warranty, and a permanent change. Most people convert an older or used camera rather than their main one. See What Camera Should You Convert to Infrared?

Lenses and Hot Spots

Many lenses produce a bright hot spot in the center of the frame in infrared, converted or not. In general:

• primes are better than zooms
• vintage lenses are better than modern ones
• wider apertures are better than smaller ones

Research a lens before you use it. The Infrared Lens Database is a good place to start. If you already have an image with a hot spot, see How to Fix Infrared Lens Hot Spots.

How to Shoot with an Unconverted Camera

1. Shoot in midday sun. Harsh, full sunlight is ideal for infrared. Clouds, shade, and the golden hour all reduce contrast.
2. Compose before adding the filter. The view is hard to see once the filter is on.
3. Use base ISO and aperture priority. The histogram works normally in infrared.
4. Open up the aperture. Diffraction starts sooner in infrared than in visible light. Use one stop wider than your usual landscape aperture. If you don’t know it, use three stops wider than the lens’s smallest aperture, for example ƒ/8 on an ƒ/22 lens. See Diffraction in Infrared Photography.
5. Focus after adding the filter. Infrared focuses differently than visible light. Don’t trust the focus scale or a DSLR’s viewfinder autofocus. Use live view with magnification or focus peaking.
6. Shoot raw. The image on the camera will look very red, and that’s normal. Raw gives you full control of white balance in editing.

How to Edit Infrared

In Lightroom and Photoshop, the white balance slider runs out at 2000 K (or 50,000 K in the other direction), which isn’t enough range for infrared. Fix that once per camera with a custom profile made in Adobe’s free DNG Profile Editor, with white balance calibration set to -100. See Create an Infrared Custom Profile. Other editors may not need one. Then:

1. Apply the profile.
2. White balance on something neutral: white, gray, or foliage, which appears white in infrared. There is no single correct Kelvin value for infrared.
3. Add contrast with contrast, clarity, curves, or dehaze. Infrared captures a narrower range of wavelengths, so it has less natural contrast.
4. Optionally, swap the colors in Photoshop with a Channel Mixer adjustment layer. In the red output, set red to 0 and blue to 100. In the blue output, set red to 100 and blue to 0. My free Photoshop Actions automate this.
5. Fine tune the colors to taste with Hue/Saturation.

For more detail, see How to Shoot and Edit Infrared with Any Camera.

Related

• How to Shoot and Edit Infrared with Any Camera
• Five Pitfalls to Infrared Photography
• Free eBook on Infrared Photography
• Live Streams

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