Digital Infrared Photography
Text and photographs by Billy Dodson - www.savannaimages.com.
The physics and optics associated with infrared photography are well documented and readily available to anyone with access to google. The link below is from Life Pixel, the company that converted two of my Nikon cameras to infrared. It offers a succinct tutorial on the varying wavelengths of light, and the internal filters that must be removed and replaced to achieve the infrared effect.
To summarize in a single albeit slightly convoluted paragraph:
Digital cameras are equipped with a ďhot mirrorĒ that relects most of the light in the infrared range, thereby preventing it from reaching the cameraís sensor. With the conversion to infrared, that mirror is removed and replaced with a filter that allows the IR light to reach the sensor. These filters come in varying degrees of strength that record a number of combinations of infrared and visible light. The effect achieved can be unique, striking and especially useful for photographing African wildlife and landscapes.
As the tutorials in the link indicate, it is possible to convert the cameras ďdo it yourselfĒ style, but this is not recommended for a couple of reasons. Modern day digital cameras are delicate instruments, and having a non-technician plow into the internals of one of them is a near certain recipe for disaster. Also, the removal of the hot mirror changes the focusing and metering characteristics of the camera... and it takes a skilled professional to tweak and calibrate them to exacting post-conversion specifications. A perfectly converted camera should autofocus almost as well as a non-converted camera, but learning the new metering characteristics will require some practice and mental adjustment on the part of the photographer.
Before converting to IR, itís important to consider the focal length of the lens to be used with the camera. Thatís because the newly made infrared camera will be calibrated to a specific lens to ensure accurate focusing and the best possible metering characteristics. For Nikons, Life Pixel defaults to the 18-70mm kit lens. Any other lens may be used, but the IR conversion company must attach the alternate lens to the camera in order to properly calibrate it. I found that the 18-70mm lens didnít give me the focal range I needed to do my work, so after much research I settled on the discontinued Nikon 18-135mm, which was purchased used from Ebay. That lens was sent to Life Pixel along with the D90 to ensure the most precise possible focusing adjustments.
So much for the mechanics of it all.
In the Field:
Itís important to consider the ultimate effect desired when using the IR camera in the field. I define landscape photography as any shot that says more about place than it does a specific animal... so, viewed from that context, I use the IR in East Africa primarily as a landscape tool. I most certainly photograph animals in my IR images, but I usually try to frame them within the greater context of their habitat to reap the full benefits of the infrared. Iíve found the sky to be one of the most critical elements in capturing a successful image. A deep blue sky with interesting cloud patterns seems to produce the highest contrast and most striking effect (see the photo at the top of this article). Conversely, a solid gray overcast offers the least hope for a successful sky. With work, however, something in between can lead to positive results. The photograph below was shot under 90% cloud cover, but because the clouds were not formed into a solid mass, the burn tool in photoshop could be used to make the image effective. The burn tool darkened the clouds and accentuated their borders. The result is a much more interesting shot.
When possible, itís best to incorporate grass and foliage in combination with blue sky. The image below was captured at the hippo pool at Ngorongoro Crater during the rainy season. The grass was a deep green color, ideal for IR, and the sky was a perfect combination of deep blue and puffy clouds. I couldnít resist snapping several IR shots here, even though the incomparable Nick Brandt owns this spot in my opinion.
The image below was shot late in the day at Tarangire. It incorporates long shadows, an enormous and growing thunderhead, and some lovely baobab trees. I donít often pick up the IR camera this close to sunset (beautiful light makes for beautiful color photography), but with digital, it costs nothing to experiment. And in this case, I believe the experiment was a success.
A guiding principle in composing an IR landscape image is to include as much beautiful sky as possible and minimize the clutter in the frame. But as weíve established, experimentation costs us nothing and rules are always and forever made to be broken. The below shot of a zebra at Ndutu is an example of a number of violations. Thereís not much sky here, there is an excessive amount of vegetation of varying types, and the zebra doesnít contrast very well with the background. This is not my best infrared photo by any stretch of the imagination, but I believe it is passable. The purpose of including it is to demonstrate the importance of throwing the guidelines to the wind from time to time and trying something completely different.
A few notes on metering and monitoring histograms in the field. Iíve found that my most successful IR results come by overexposing my photos from .7 to 1.0 stops. The default setting is +.7, because itís better to underexpose slightly than to overexpose. But the prudent photographer must watch the histogram carefully. If the general movement of the curve is to the right, the exposure must be reduced. Generally speaking, with more sky and less foliage in the viewfinder, +.7 to +1.0 is usually a safe range. In an area with heavy vegetation, for example the woodlands at Ngorongoro Crater, with minimal sky in the composition, the exposure must be reduced drastically. Possibly even to -.3 or -.7. Obviously, with a range this expansive, the IR photographer must be attentive to exposure compensation 100% of the time.
A well-calibrated IR camera should autofocus at all F stops. But the best results seem to come when the aperture is set at F8 or smaller. I usually set my D90 to F11 and stop down from there if the light is sufficient. But this approach, combined with the default overexposure, can take the shutter speed to unacceptably low levels. Like the histogram, shutter speed must be monitored carefully and aperture or ISO changes made when light conditions so dictate.
As always, the IR images are captured as RAW files. Those files often, almost always, have a pinkish cast that is easily removed with the saturation slider in Adobe Camera Raw. Exposure adjustments are required with almost every image and these are also best accomplished in ACR. Once thatís done, the image is opened in Photoshop.
My first action in PS is a careful review of the image to see if dodging or burning is required. The next step is a levels adjustment to improve contrast. Further adjustments, usually accomplished in layers, depend on the quality of the image and the desires of the photographer. I do a final review for excessive noise, which is removed with the Topaz Denoise software plug-in. The last act before closing the file is sharpening, which is accomplished with the Unsharp Mask tool in PS. Once Iím happy with the photo, and if I deem it marketable and printworthy, I name it and save it as a master file in my print folder.
The story doesnít necessarily end there. At some point, I may want to tweak the photo further... perhaps add some sepia toning or vignetting to enhance the power of the image. Nik Silver Efex is the software of choice for these tasks. Iíll save detailed discussion of Nik Silver Efex for a future article.
There are a number of ways to achieve the infrared photo effect. Some IR film can still be found, external filters for DLSRs are often employed for this purpose and software can be used to transition a normal color image to something near IR. But in my estimation, the most dramatic IR effect straight from the camera is best accomplished with a converted DSLR as described in the opening section of this piece. It is a fun, exciting and challenging technique that affords the willing photographer yet another opportunity to improve creativity and refine existing skills.
Take care, Billy.
All images with permission to publish on Safaritalk courtesy and © Billy Dodson.