If you intend to obtain IR photos without using an expensive filter, then this tutorial is the right one for you!

Infra and ultra

Light can be defined as an electromagnetic wave whose different wavelengths determine its colour.
Infrared light has a much shorter wavelength than ultraviolet light. In simpler terms, infrared light is light which cannot be seen by the naked eye situated below the red end of the spectrum [hence the infra prefix].
Ultraviolet light is situated above the violet end of the spectrum [hence the ultra prefix]. It is often used in solar parlours in order to get a good tan. For more info, check out the Infrared article.

The tutorial
This tutorial will focus on the Photoshop part of obtaining an infrared photo. The photo-filter way of obtaining it will be discussed in another tutorial.

Step I - The base image

The base image is that of a walnut tree. Using plants is a good way of illustrating IR as they reflect it.

Step II - Mixing the channels

Once you have your photo, duplicate the background layer.

Next, go to the Image>Adjustments>Channel Mixer menu. This allows us to work on the RGB channels in order to obtain our infrared effect. Note that you should tick the monochrome box so that the image is turned into grayscale.
Now that you know how to operate, it's time to set the sliders to more appropriate levels. Set the Red slider to 100%, Green slider to 200% and Blue slider to -200%. Once this is done, the green will be highlighted whereas the blue and red will be darkened.
By the way, make sure that the Total remains to 100%. Otherwise, the image will have a posterized look [the intensity of the colours will make the image look like an old 256-color photo].

The final image?

Yup, this is it. Note how the green leaves have turned into white leaves. This reflects the intensity of IR radiation.

Step III - Colour IR

This optional step involves the colorization of an IR photo. To do this, you must make two additional copies of the IR photo and apply two different effects.

On the first layer, apply the Screen effect and on the second layer apply the Linear Burn effect. The order of the layers should be the following: first the Screen layer, then the Linear Burn layer.

The [other] final image

The colour IR image is blue around the leaves, where the sky is.

See Also:

• Infrared
• Filters
• Photo Filters