This article is a simple introduction to Infrared Photography. For those of you who find it interesting I’ve placed some links to more detailed and extensive sources at the end of this.
What is Infrared Photography?
First, lets more clearly define what we’re talking about. What we refer to as light is electromagnetic radiation with wavelengths of 400 to 700 nanometers. At the 400 nm end of the spectrum, the light appears violet-blue to us, at the 700 nm end its deep red. Wavelengths longer than 700 nm are termed infrared. The infrared spectrum is divided up in different arbitrary regions depending on the field of science doing the dividing (astronomy, communications, weather, etc.) but for purposes of photography, what we term infrared is really the near infrared spectrum: 700 to 1400 nm wavelengths. (The type of infrared used for thermal imaging for military and industrial purposes is in the far infrared from 8,000 to 15,000 nm).
Infrared photography and videography came into fairly widespread use during World War I and probably reached its peak in the 1960’s as part of the ‘psychedelic’ look. Its been used in cinematography for years for a variety of effects. (The most common of which is ‘night scenes’ in old black and white B movies—you ever notice those ‘night time’ scenes where the sky is pitch black but the actors and scenery seem almost glowingly bright? The sky appears black in infrared.) In those days special IR sensitive film was used, along with a filter over the lens to block out visible light.
The sensors in digital cameras are just as (if not more) sensitive to IR light as they are to visible light, so the camera manufacturers place an infrared filter over the sensor to block out IR light, leaving the camera to only ‘see’ visible light. Some of these filters are less efficient than others so its been known for a while that certain cameras were more sensitive to infrared light (the Leica M8, for example, leaked infrared so badly it caused some false color problems). Certain video cameras used the IR sensitivity to help them in dark situations, the Sony “night shot” effect. You don’t see those cameras made anymore since some Japanese teenagers found that many women’s swimsuits were transparent in the Infrared spectrum and quickly marketed ‘peeping tom’ infrared filters for them. I don’t have any firsthand knowledge but I’m told those old videocams still sell for quite a premium on eBay.
Back to the subject. If you put a filter over the lens to block visible light you could take a picture in near infrared with most digital cameras. Because the infrared filter was still present in the camera, only ‘leaked’ infrared light got through to the sensor and exposure times were quite long, so the technique was mostly suitable for tripod-mounted landscape shots. Still, it allowed photographers to take infrared images without using very expensive and difficult to handle infrared film and became fairly popular.
In the last few years a number of companies such as Maxmax , Lifepixels, and Precision Camera have begun modifying digital SLRs by removing the infrared filter and/or replacing it with a visible light filter. These ‘IR modified’ SLRs now take pictures in the near infrared band rather than visible light. With a converted SLR the photographer can take infrared images just as they would visible light images. The camera will autofocus, autometer, and exposure times are normal, or even a bit shorter than with a standard SLR. A tripod is no longer needed.
So Who Shoots IR?
Landscape photographers are the people who use IR the most. The primary characteristics of an IR image, bright white foliage and dark skies with white clouds, provide a very different look and mood to a photograph.
IR photographs are usually converted to a black and white look, but in some cases are left in color (its a false color provided by the camera’s sensors and software) to give an unusual look.
For some much better examples of IR landscapes with false colors, visit Jeffrey Klassen’s Gallery
A more adventurous group uses infrared for artistic portraits, nudes, and wedding photography. Here is an IR wedding gallery (Scott Nelson). While not usually used for the primary shots, the dreamy IR look definitely provides something romantic and different. Wedding photographers I know who use the technique say that brides usually only pick one or two IR shots for their album, but are quite likely to pick an IR shot for a large print. Because the red and blue hues that make up most skin blemishes are not visible in infrared, an IR portrait or nude is noted for very smooth, porcelain skin. This, along with the softer focus IR shots usually have, can be very flattering to the model. Done poorly, it gives a very scary, ghostlike appearance.
IR portraiture is quite difficult to master, however, and definitely not for everyone. Remember that make up, hair dye, tattoos, etc. are all designed for what they look like in visible light, not infrared. Hair dye for example is usually colorless in infrared: the mother of the bride might be most upset when the IR photograph reveals her real hair color is white. Certain metallic based makeup can look like mirrors in IR, while other subtle shades of mascara may show up jet black. Oh, and cheap polyester tuxedos aren’t black in IR, they’re rather fluorescent purple – not attractive. Don’t ever attempt IR wedding or portrait photography without making a few quick test shots and having a non-IR backup plan.
What Do You Need to do IR Photography
Well, it can be done with nothing more than an IR filter over your lens, a sturdy tripod, and a fair amount of exposure time. But to really enjoy IR photography you’ll need an SLR converted to IR. Conversions differ by what type of replacement filter is used: a 665 nm filter allows IR and some color (normal) light to hit the sensor, giving a color IR camera (the colors are false, but often interesting). A 720 nm filter lets very little normal light through and all of the infrared light, giving an image suitable for black and white infrared images, or images with just a touch of false color. An 830 nm filter is truly for the infrared look only: skies are dark black and foliage bright white with very little false color. Most photographers who really get into shooting in IR have their previous camera body converted to IR when they upgrade to a new body. This can be done for a few hundred dollars. Or you can rent one of our IR converted bodies if you want to experiment with IR for a while, or if you only want to shoot IR occasionally.
Lens choice is important: the best lens for visible light isn’t necessarily the best lens for IR. Because its wavelength is longer than visible light, infrared doesn’t focus exactly the same. Zoom lenses generally struggle to focus IR light a bit more than primes, but in any case ultra sharp images aren’t the point of IR photography and sharpness isn’t that important. Usually shooting at f/5.6 to f/8 gives a sufficient depth of field to assure reasonably sharp images. Lens flare and infrared hot spots are more of a problem and some excellent lenses are horrid in IR because of these. We’ve listed some good lenses with each of our IR cameras. A much more detailed list of the strengths and weaknesses of various lenses for IR photography can be found at Diglloyd Guide to IR Photography There’s a small fee for this guideline, but if you’re really interested in IR its a superb resource.
Finally, IR photographs will require some postprocessing in Photoshop or a similar program (for this reason they are best shot in RAW so you can get the maximum benefit from postprocessing). Contrast boosting and converting to black and white or duotone images using the Channel Mixer or other techniques will yield the best possible photographs.