Some things go in cycles, and infrared photography is one of those things. It’s kind of a quirky way of recording an image — you record only the infrared part of the spectrum reflected from your subject.
A bit of history: Once upon a time we all shot film. Infrared film came in a number of different varieties. The primary distinction was color or black & white and if you see IR images now, you are probably looking mostly at black & white. The black & white infrared film had the eerie characteristic of haloing or blooming around the highlights, making the image look not only somewhat negative but also gauzy or even ghostly.
Fast forward to digital. The way people started out doing digital infrared was to use something like an R72 or an 87 filter — a deep red that cut all the light except the infrared. It has an immense filter factor, so exposures have to be extremely long.
Infrared Sensor Filters
At this point, enter a company called LifePixel. They are based in Washington State (USA) and will convert your digital camera to shoot only infrared. I mean only infrared. They do this by replacing the highpass filter that normally goes over the sensor with one that only allows the infrared part of the spectrum to pass. Sound familiar? But the beauty of this solution is that exposures are of normal duration — i.e., if you were shooting f/8 at 125th of a second with your normal DSLR, then it would be pretty much the same with the converted one. This reduces the need for extraordinarily long exposures.
Color Infrared
Here is an example of an image shot in raw on a converted Canon 20D with no post-processing:
You may notice somewhat brown skies along with the signature white trees and ghostly look associated with infrared. The image is pretty much monochromatic. However, the cut filter does allow the sensor to detect a bit of color and since it is recording in RGB, it doesn’t look quite like a black & white infrared. There are two directions to go with this. The first is to do some smart juggling in Photoshop:
For this image, I did a bit of levels adjustment to bring up the whites and darken the blacks, added an S-curve to enhance contrast, then the important part: Used the Channel Mixer to mix red to 100% blue and blue to 100% red. Green is left alone. This makes the sky blue and gives the appearance of a color infrared. You can read a bit more here.
Black & White Infrared
I’m not crazy about the weird color infrared look, preferring, instead, the stark black & white look. Here’s the same image done as a black & white.
For this image, I simply took the image from the first version, popped it into Nik Silver Efex Pro, made a few adjustments, and voila!
Conditions for Infrared
Infrared light does not reflect off everything, so don’t think you’re going to make all kinds of keen night shots and so on… You have to test and try and feel out what looks best in infrared. One thing you will see right away is that foliage is wicked cool in infrared. It’s so easy, you’ll find yourself developing a magnetic attraction to all things green even if you are allergic to plants. Other subjects that are absolutely amazing in infrared are structured cloudy skies. That is, thunderstorm style clouds where there are darker and lighter areas of cloud. Just plain overcast won’t be as much fun.
Finally, cityscapes can be eerie in the best possible way in infrared, but as with many infrared subjects, your mileage may vary. These are particularly sensitive to the direction of the light so some experimentation is necessary to get some usable shots.
Summary
Infrared is a really fun technique and one that really cannot be duplicated in post-processing. It’s the result of a particular part of the spectrum falling on the sensor — this part of the spectrum is absent once a digital image is captured on a normal camera.
However, converting a camera to infrared means you are sacrificing a camera. One use only, which is why I mentioned that these images were made on a 20D — obviously, this was an older camera and one that could be sacrificed at the altar of infrared.
One additional change that should be made is that of focus. This is important to understand. Different bandwidths of light are focused by the lens at different locations. Because infrared has a wavelength longer than that of visible light, lenses are not optimized to focus it at exactly the sensor plane. As a result, you either need to modify your lens to focus appropriately, or you need to take this into account yourself by refocusing manually. Because you cannot perceive infrared light with your eyes, you absolutely cannot focus for infrared by eye. LifePixel performs this modification to lenses, which makes it an obvious choice as opposed to using an IR filter.