The Blog of Patrick C. Cook

The photography blog of Patrick C. Cook.

Winter Wonderland

This scene looks like a winter wonderland, doesn't it?


Actually, it's a hot summer day in Massachusetts with lush trees and grasses all exploding with green colors of various shades and intensities. The primary reason why this image shows so much white color is because plants reflect near infrared, which a digital camera that has been converted for infrared is able to record. But there's a bit more to the story.

Plants reflect the green portion of the humanly visible spectrum of light, which is why the human eye perceives many plants as green. However, the plants are not actually green, rather they are reflecting green. Digital cameras converted for near-infrared have a filter placed in front of the camera's sensor that blocks the majority of the visible spectrum and allows only a portion of the near-infrared spectrum through the filter. In some conversions, the chosen filter allows some of the visible spectrum to also pass through the filter, as is the case of the camera I used to capture the above image.

In this case, because I used a converted camera with a 665nm (nano meter) near-infrared filter, I was able to process the image to bring out the blue in the sky because a 665nm filter allows a portion of the red visible spectrum to pass as shown to the left. (Note: The 850nm filter blocks all of the visible spectrum.) The image processing trick to obtain a blue sky from red is to use Photoshop's channel swap tool which allows you to swap red colors with blue colors, effectively changing the red in the image to blue. The end result is a blue sky in the image (which is much more appealing than a red sky).

I enjoy infrared photography because the final image is not only a product of field work, but also processing. In the field you mine for images in the near infrared spectrum, not quite knowing what you have in the field - you just never know what gems-in-the-rough you'll return from the field with, to be polished with amazing software tools available to us.


Why I Love Infrared

Since I jumped into digital infrared photography about a year ago, I find myself preferring to shoot infrared more often than color. There are several reasons why this personal preference has been developing for me, but I'll focus on one reason here. What I like about infrared photography is the challenge that stems from two factors; first is that in the field you can't be completely sure what image you've actually captured and second, the image is seldom ready for viewing until it has been processed at the computer.


The first challenge, not being able to know what you have in the field, is rooted in modern digital cameras having been designed for the visual spectrum of red, blue and green, i.e., designed to avoid the infrared spectrum. The result is that your camera's color LCD provides a poor simulation of the image. In addition, the camera's viewfinder will not show you what the sensor will capture, which where the color of the visual spectrum is filtered out. Thus, a typical DSLR, being intended and designed for color photography, is actually harder to use for infrared shooting even after having been converted for infrared. I might add that we see in the visual spectrum, so the red, blues and greens that we perceive will not be what we capture on the camera's sensor - that alone is disconcerting,

The second challenge is that an infrared image is often not usable as captured. The exception might be when the camera is converted to a straight infrared filter at 850nm, in which case the filter blocks all of the visible spectrum and the photographer doesn't have red, green and blue color components in the image to deal with. However, the 590nm, 665nm and 720nm filters each allow some portion of the visible spectrum to pass to the camera's sensor, leaving you with images with a color component (predominantly red). That, in turn, requires processing at the computer to handle the color portion of the image.

Overall, infrared photography is a welcome challenge in digital photography - you can't just point-and-shoot and expect usable images. You have to think through each image. You have to "think beyond color". And your photography effort almost always extends back to your digital darkroom to complete the process. I find infrared photography exhilarating because of its level of unpredictability as well as its artistic and technical challenges.