In this tutorial we go step by step through the processing of infrared images from an unconverted digital camera.
Once you have shot infrared images with your digital camera you will need to do some processing to make them useable. In this article we will go step by step through the process, showing the options you have as you go.
The processing of digital infrared images is one that offers huge and almost infinite creative options. While this tutorial is illustrated by screenshots from Adobe Photoshop CS4, all these techniques can be done in CS3 and most can be done in earlier versions of Photoshop and in other programs, like Paint Shop Pro. So if you use one of these you will be able to do these processes, just the details of the exact commands will vary.
As we saw in the previous article, Shooting Infrared Photography Step By Step, your images will look very strange straight from the camera. You have two different directions you can take: produce a monochrome image or go for a false color image. We will examine these separately.
If you have chosen a single channel to expose for when you were shooting, the first approach option is to do a monochrome conversion from just your chosen channel.
Open your image in Photoshop, if necessary doing any adjustments you want in Adobe Camera RAW. Remember that you may be able to claw back any burned out highlights or blocked up shadows with the exposure, recovery and blacks sliders.
It is better to setup ACR to pass a 16-bit image to Photoshop as this will give you more headroom to make adjustments without adversely affecting tonal graduation.
Now open up the channel palette and select just the channel you wish to use.
If you use Image -> Mode-> Monochrome Photoshop will convert your image to monochrome using just the one channel.
You will probably find your image is a bit flat. So the first step is to adjust the black and white points. Use Levels to do this. You can set the black and white points to whatever you want. So you can maintain full control over the highlights and shadows and just how they look. Note that I position the dialog so I can still see the histogram panel while I make the adjustments to ensure I am not going to introduce clipping.
At this point you can take the image anyway you like, such as by applying curves to increase contrast where you want it or doing local adjustment using dodge and burn or other approaches.
Approach 1a – Simulate Halation
Many people like the glowing highlights look that came about with Kodak Highspeed Infrared Emulsion because of its lack on an anti-halation coating. You can simulate this with the following approach.
Duplicate the image layer by dragging it to the New Layer icon.
Apply a pretty heavy Gaussian Blur filter to this duplicate layer.
Now change the blending mode of the top, blurred, layer to Lighten or to another mode that works for you. Lighten will simply apply the glow to the highlights without blurring the shadows.
You can then use opacity to control the degree of the effect.
Another alternative is to add a Layer Mask to this blur layer.
Then paint into the layer mask where you want to hide or reduce the effect.
You can choose to combine the channels rather than select just one to do the BW conversion.
Open your image up in Photoshop and do an individual channels level adjustment by either selecting one channel at a time in the Channels palette and then Levels.
Do Image -> Adjustments -> Black & White
Now you can mix the channels together and see the result in the main image window.
Using a single image we can create false color.
Open the image up in Photoshop.
Do an individual Levels on each channel. You can do this by selecting each channel one at a time in the Channels palette or by using the facility of the Le
vels dialog to work on individual color channels.
This gives you an image with subtle color
At this point you can leave it like this or further develop the image. One way to develop further is to increase the color saturation or vibrancy to make the subtle color more obvious.
You can perform channel swaps to shift the color. Say you want to swap red and blue channels. You can click on the red channel. Do a Select All and then copy to the clipboard.
Click on the New Channel icon in the Channels palette and paste the red channel in there.
Then copy the Blue channel and paste it in the Red.
Then copy the temporary channel (what was the Red) into the Blue and delete the Alpha 1 temporary channel.
Further adjustments can be made to individual channels, such as here where by lightening the red channel I add more obvious red to the image.
There are, of course, many other ways to add false color in Photoshop, such as by using the channel mixer.
An innovative solution to creating false color images, that look somewhat like the old Infrared Ektachrome false color film IR images did, requires that you take two images. One image should be a normal, visible light image without your infrared filter and the second is an infrared image. Life is much easier if these are both shot on tripod and in alignment, so care should be taken when you attach the IR filter.
The approach is to open both images in Photoshop and swap channels from the infrared image into the color one. To create the classic Ektachrome effect it is generally the red or green IR channel that you move into the red channel of the color image, to turn the foliage red. But other possibilities also exist for other effects.
Now because of the channel swapping between the two images you need to be careful of either camera or subject movement between the two shots, so you would wish to do this as quickly as possible. With landscapes, days of high wind can be a problem, as can other causes of movement, such as cars, people, etc.
The specific sequence of steps is shown below:
Select the images you will use in Bridge, Photoshop or some other program.
Now you will have your two images open in Photoshop.
Select the individual channel in the IR image that you want to use. In this case I am using the green channel. Do a Select All and then copy it to the clipboard.
Select the channel you want this put into, usually red, and do a Paste.
Now examine just the colored image to see if there is any misalignment.
If there is a misalignment select just the red channel (but make sure the other channels are visible by clicking on the eye next to each channel) and use the move tool to move the red layer into alignment. This is often more easily done at 100% and focusing on a distant part of the scene that does not move.
And this is the result.
Other results are possible depending on the actual IR channel you choose. Here I have used a red channel. You can see the interesting color effects you get when things like leaves move.
Here are a couple of other examples
Remember you are not limited to RGB. Here we have the color image in LAB mode and I paste the IR image into the L channel.
And here into the a channel.
I hope you have found this article useful and will get you going on working with a subject that is my passion, digital infrared photography.