Infrared Techniques with Digital Cameras

Capturing color—from the olive tone of a model’s skin to the deep red of the desert sand—can be essential to producing a strong photograph. But there’s a whole range of light beyond the visible spectrum of a standard snapshot: Using infrared light, advanced photographers are creating innovative photographs from everyday scenes—and with a few simple steps, you can do the same.

Discovering Infrared and Its Applications
Astronomer William Herschel discovered infrared light, invisible to the naked eye, back in 1880. Infrared light lies just below visible light in the electromagnetic spectrum, meaning its wavelengths are closest to that of the color red—and it’s easy to remember when you know that most infrared waves come from the “heat” of thermal radiation.

The first infrared photograph was produced in 1910, and more than one hundred years later, photographers are still using this scientific discovery to expand their visual horizons. And this technology is certainly not limited to the realm of the still photograph: Art curators, for example, use infrared light to explore and document the authenticity of paintings; scientists to enhance weather and satellite photographs; researchers to study animal, insect and plant behavior.

Infrared photography is a surefire way to create great photographs from ordinary subjects, and it can be done with film or digital cameras, with a black-and-white or color image as the base. Best done in bright daylight, infrared photography is a great way to enhance subjects in images captured between sunrise and sunset, the two “golden” times for light. While infrared photography was possible with film cameras, it required expensive, hard-to-find film and difficult developing procedures. New digital technology, however, makes it easier than ever to spice up a photograph with a infrared light: All you need is a simple, inexpensive filter and a little time.

How to Choose an Infrared Filter
An infrared filter is a piece of glass that attaches to the front of your camera lens, much like the ultraviolet filters that come standard with many cameras. To get started, you will need to buy infrared filters and perform a few tests to determine your digital camera’s particular sensitivity to infrared light. The images in this article were shot with the Nikon, but all digital cameras have infrared sensitivity because their sensors are receptive to light outside outside the visible spectrum. Results will differ from camera to camera due to the mechanics of different models.

Once you’re comfortable with the camera, you can begin experimenting with different types of infrared filters. Tiffen makes a number of filters, as do Wratten, Schott and Hoya. The range of numbered filters allow you to capture light at different wavelengths within the infrared spectrum, as you can see in the image below. There are two main types of filters used for infrared photography: translucent (red), which allows in some visible light along with infrared light, and opaque (seemingly black), which allows no visible light to enter the lens. As the filters move from visible to infrared light, the proportion of visible and infrared light they let in changes: The Tiffen Red 25 filter lets in some visible light along with infrared light; the Tiffen 18A filter lets in slightly less visible light along with infrared light; the Tiffen 87 filter lets in only visible light.

The translucent or “false” filters (#25, #29 and #70) filter out some of the visible light but allow enough through to focus. The opaque or “true” filters (#18A, #89B, #88A, #87, #87C, #87B and #87A) cut down so much of the visible light that you’ll need a tripod, and you must pre-focus the camera before putting the filter on. At the same time, focusing your camera with the “true” infrared filters and ensuring good depth of field are less of a problem with digital cameras, because the small sensor allows for greater focusing latitude.

The translucent red filters produce interesting effects in both color and black and white, and they can be used for action photography. Since they allow some light from the visible spectrum into the image, infrared filters make for dramatic color effects when you adjust them in Photoshop.

The opaque or “true” infrared filters are better suited for black-and-white imaging, but some subtle effects can still be obtained in color. You will need a tripod to use the opaque filters—again, you’ll need to focus before putting the filter on, and the shutter speeds are typically very slow. Unlike the translucent filters, the opaque filters completely cut out the visible light where the visible and infrared parts of the spectrum overlap, resulting in long exposure times.

There’s a great deal of controversy about “true” versus “false” color in the infrared photographic community. In fact, there is no such thing as “true” or “false” color—after all, infrared filters are making invisible light visible, so anything we produce in color or black and white is an interpolation. You can’t hear the high-pitched whistle that a dog hears, nor can it be described. It can, however, be recorded and interpolated, so that we have an idea of the quality of the sound causing the dog’s reaction. The same is true with infrared film: We can only guess what the infrared spectrum looks like, and any images we get out of the process are merely visual representations of non-visible light.

Determining Your Exposure
Due to variances in sensors, digital cameras will be sensitive to different parts of the infrared spectrum, and individual models will require certain exposures and filters. The simplest way to check your exposures is to run a test: Set your aperture at a relatively high depth of field, and bracket each frame in several stop intervals to see which works best. Bracketing requires that you take a series of exposures at different shutter speeds. Since you’re not paying for traditional film, I recommend running a widely-spaced bracket.

For this article, I used three filters, two of them opaque and one translucent (red). I began my tests for each filter at the correct setting of 125/f9.0. Then, I put the filter on took frames with my shutter set to 1/60th of a second, 1/30th second, 1/15th second, 1/8th second, 1/4 second, l/2 second, 1 second, 2 seconds, 4 seconds, 8 seconds, 15 seconds and 30 seconds. This was done for each filter, and the times were recorded.

It was relatively easy to determine which of the images had a “normal” exposure (“normal,” of course, being a relative term with infrared photography). In many cases, several of the bracketed exposures made for great-looking pictures—so even if you run a test for each filter, always bracket as well. I found that exposures longer than four seconds produced noise in the image, but even this effect was pleasing in color.

Subjects reflect infrared light differently, and the variations between exposures can be a fascinating experiment. To see which exposures and filter combinations are going to work with your camera, simply import the exposed images into a database program like Extensis Portfolio, Canto Cumulus or, in the case below, Nikon’s Capture software. The biggest problem you’ll encounter? Choosing from among the many images you like!

As mentioned above, the red visible filters (#25, #29, #70) allow enough visible light to pass through the lens, so you can use your hand-held camera and get spectacular results. In the illustration below, a Tiffen Red #25 was used on a bright day at 250th of a second at f/5.6. The normal exposure without the filter would have been 1000th of a second at f/5.6.

 To adjust the exposure after the shot is taken, bring the image into Photoshop (or similar image-editing software) and select “auto image adjust.” Using an image correction program, you can achieve the soft, diffuse lighting associated with infrared photography, but you can also achieve a stunning color array—a “false” color that is truly attractive.

Opaque and Translucent Filters
As mentioned earlier, opaque filters are designed to screen out almost the entire visible light spectrum, so images produced with them would look black to the naked eye. To use them, you’ll need a tripod, and you will have to focus and compose your picture before putting the filter on the lens. The #18A filter produced a subtle color image with low contrast and required a six-stop correction in exposure (check this against the chart above). The color images produced by the #18A filter in this sequence are perhaps more interesting than those produced in black and white, but every subject and exposure produces new and fascinating results.

True Infrared Filters
For the most dramatic effects in black and white, you’ll need to use the #82A or the #87 opaque filters, which allow very little visible light into the image. The images below were taken on a sunny day at mid-afternoon with a #87 filter. The results with the filters are typical of the surrealistic effects that infrared purists would call “true” infrared. In the color image, you will notice very little red, as most of the visible light has been filtered out, leaving only the infrared spectrum. The black and white images are stunning examples of pure infrared light.

Simulating Infrared
Infrared filters alone will produce fascinating results, but Photoshop can help to simulate or even further exaggerate the effects of the filters.

In the following series, you first see a normal color photo of a lighthouse at the St. Michael’s Museum in Maryland. I then put a Tiffen Red #25A translucent filter on the lens to achieve the second picture. The third photo was converted to black and white through the “Image – Mode – Black and White” tool in Photoshop. (You can also select “Image – Adjust – Channel Mixer” to quickly change the image to black and white.)

As you can see from the image above, changing an image to black and white in Photoshop is no different from using a black-and-white camera setting. In the sepia image below, I first applied the “Diffuse Glow” Photoshop filter to the whole image to enhance the clouds and blur the whites. After that, I brought the image into “Duotone” mode and applied an exaggerated “Sepia #4” tone to the image. It has the diffuse whites common to infrared but lacks the deep tones in the sky.

There are several techniques to simulate infrared filters in Photoshop. The “Channel Mixer” tool can produce an effect similar to color infrared images, but it’s even easier to simulate infrared effects in black-and-white—all you need is the “Diffuse Glow” tool and extra contrast. There are also certain programs like Adobe Lightroom that have built-in tools to create an infrared-like filter on an image. Despite the convenience of editing at home, using infrared filters can be a far more rewarding, spontaneous experience. Finally, be aware that certain cameras are more sensitive to infrared light others, and experiment with your camera.

 Useful Links

The Mansurovs

Infrared Photographs on BuzzFeed

Andy Finney

RIT’s Infrared Tutorial

Simulate Infrared in Photoshop