Infrared Photography

Homemade lenses are not limited to the visible light domain. Infrared photography can also be used with homemade lenses. In fact, there are properties of homemade lenses and infrared photography that complement each other very well. For example, spherical aberration from simple uncorrected lenses tends to drastically reduce contrast. This is particularly true in landscape shots in which the light from the blue sky can wash out all the detail of the image. On the other hand, landscape images taken in the infrared part of the spectrum tend to have increased contract because the foliage is brightened due to its reflectivity to IR, and the sky is darkened due to less scattering of IR light. Therefore, when landscapes are shot in IR using homemade lenses, much of the loss in contrast and blue haze from the homemade lens is eliminated by the properties of IR photography. What remains is a soft, diffuse, and rather dreamy look.

I am not an expert on infrared photography. Far from it. I am just beginning to explore this very interesting area. Therefore I will not attempt to provide any in-depth tutorial on the topic. Fortunately, there is plenty of good information available on the web. For people who have not tried it, I will only add this: Digital infrared photography is not hard at all. In most cases all it takes is the purchase of an infrared filter such as the Hoya R72 or the Tiffen 87. Note that today's DSLRs all seem to have a sharp filter designed to stop IR from reaching the sensor. But just enough IR gets through to make IR photography possible with these cameras. Note that exposure times will need to be very long. 30 second exposures are common. I don't consider this a big problem as long as you use a tripod.

First Results

This image was taken using a two element 105 mm f/ 2.8 lens. The elements are mounted in old filter rings which made it easy to attach the two elements to each other and then to bellows for focusing. The filter rings had the additional advantage of being already threaded to accept an IR filter without any additional construction. In this case I added a Tiffen 87 filter. I used the channel mixer in photoshop to create the final monochrome image with a few final adjustments to the levels and curves.

False Color Infrared Imaging

Digital Infrared photography can be used to produce monochrome or color images. Color images will always be false color. There is no such thing as "red IR" or "green IR" or "blue IR".

However there are ways of manipulating the limited color information in digital IR photos to produce beautiful surreal images. Typically, an image produced with an R72 filter, which allows a small amount of visible red light to pass through, will be manipulated by either shifting the white balance or swapping the red and blue channels.

I decided to try a very different approach to false color infrared photography. By taking three photographs of exactly the same scene: one with no filter; one with an R72 filter (720 nm cutoff); and one with an 87 filter (795 nm cutoff), and then combining just the red channels of these images, I can produce a composite false color image in which the spectrum is blue shifted. Red light becomes blue. Light on the red/IR boundary becomes green. And infrared becomes red.

Applying this Infrared - Blue Shift technique to another scene shot with my homemade 2 element f/ 2.8 lens resulted in this image.