Mission Implausible

Nikon D90 False-color Infrared Image

I love it when someone tells me I can’t do something. It makes me want to try all the more.


Well, they haven’t exactly told me I can’t do it, but some have eluded to the fact that the D90 is “not an infrared-sensitive camera”. In other words, it’s a “strong IR filter camera”, and that to capture infrared images on a D90, it first has be converted by removing the hot mirror filter over the sensor, and replacing it with a clear glass filter. The clear filter will pass IR, UV and visible light, so I will always have to use a filter of some sort; a threaded hot mirror for visible light and UV, or an R72 or 89a for IR. Sorry, not going to do that to a new camera with a six year warranty.

So, before I go investing in a used D50 body (with a much weaker hot mirror filter) for use as is or as an IR conversion, my mission is to see just what the D90 can capture in the infrared spectrum.

Time exposure is not really a problem in my mind. Landscape photography, in which IR excels, lends itself well to time exposure. Infinity or near-infinity focus means wider apertures, so the exposure times could be quite short compared to pinhole, another of my passions. Windy days and flowing streams will impart their own aesthetic to the image.

But the color is an issue. Don’t get me wrong, I love black and white infrared. But false-color infrared images really intrigue me. I feel I have to master the color before I can go on to the black and white. There’s a unique beauty to “false color” images which I aim to achieve with the D90.

The trick is starting out with the most neutral image possible, which involves careful white balancing. But the secret weapon is the L*a*b* color space. Only here can I control the color without affecting the exposure. Directly from the camera, the “latent” images are a pleasant sepia tone. But after further white balancing and L*a*b* processing, the colors appear. Each image is unique, and has the ability to produce many different variations, so the results are pleasantly unpredictable. I’ve built several actions which allow me to control each image through non-destructive layers.