OPTICS GEEK

Digital infrared photography made easy

Infrared cameras capture color information by masking individual pixels with colored filters. These red, green and blue filters are meant to mimic our human visual sensors, but they also have an unfortunate characteristic: they are transparent to near infrared radiation. If this infrared light were allowed to strike the pixels, color purity would be tainted. To counter this, commercial camera manufacturers put in an additional filter that passes only the light that we can normally see. This allows digital cameras to produce excellent color purity, but the infrared light is absorbed and bounced away from the sensor.

In actuality, most digital cameras have some level of sensitivity to infrared light. If you aim your camera at your television’s remote control, you can see the infrared LED flashing when you press the button. You can, in fact, take infrared photos with these cameras, using a special filter that passes only, or most only infrared radiation. Unfortunately, this cripples the sensitivity of your camera since you are using only a very small amount of the light available to the camera.

An InfraReady camera with an infrared pass filter is 400 times more sensitive to infrared radiation than an unconverted camera.


You can, of course, take photos with an unconverted camera, but you are going to have frightening long exposures to get any good results. This takes you well out of the realm of hand-held photography, and does not allow for creative filtering. If you use anything but an infrared filter, you will swamp the sensor with visible radiation without achieving an infrared exposure.

Example of handheld InfraReady compared to stock A480:

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InfraReady with infrared pass filter. 1/50th of a second exposure.
Canon A480 with infrared pass filter, and its unaltered infrared blocking filter, 1-second exposure.

The InfraReady Camera


The InfraReady camera is special because it has the masking filter removed, and replaced with a piece of optical glass manufactured to maintain the optical prescription of the camera lens in order to maintain proper focusing and image quality. This glass is tightly controlled in its thickness, flatness, parallelism, surface quality, and it is anti-reflection coated to greatly reduce internal reflections in the visible and near-infrared spectrum.

The end result is a camera that is balanced in the infrared and visible spectrum. The InfraReady opens the way to achieving very creative results because you still get the ability to capture color. In the above example, using a normal camera with an infrared filter, you only allow infrared light in. This creates a monochromatic image, with very little to no creativity to be had in the world of color: you are limited to composition and shade only. The infraReady, along with colored filters, gives you much greater control. For example, a blue filter can allow blue and infrared radiation to strike the sensor, bringing out the blues in the sky, while still allowing some of the infrared alien light to strike the sensor.
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Above, an InfraReady with a green filter (left) compared to a Canon A480 with a green filter and the stock infrared blocking filter still in place (right).
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Here an InfraReady with a blue filter (left) compared to a Canon A480 with a blue filter only (right), and the stock infrared blocking filter in place.

What is infrared photography?


Human vision encompasses a very small portion of the electromagnetic spectrum. There is blue at one end, green in the middle, and red at the opposite end. There is a world of information beyond this range, but our human eyes simply cannot perceive it. Without some artificial means, this world is invisible to us.

Some compare light, which is thought to be oscillating, to be like the strings of a guitar. We talk about this light by the distance between peaks of this vibration. Violet light has a wavelength of 420 nanometers (nm), green 530nm and red 700nm. The advent of digital cameras can open this world to us. The sensors in today’s digital cameras actually have good sensitivity to light out to about 1000nm, or what we call the near infrared spectrum. But for technical reasons, digital cameras block this light from ever reaching the sensor.

This normally invisible light illuminates a world that is alien to us. Foliage and bark take on a surreal appearance, water turns opaque, skin takes on a soft and luminous, almost frail appearance. Without special equipment, like the InfraReady camera, you will never be able to witness this strange world.