Although infrared cameras capture little or no visible light, you still produce a color image in your camera. You can get creative with these colors depending on the type of conversion you have and your software. One favorite technique is the “blue-sky” effect. In this post, I’ll explore a couple of ways you can create this effect with different software packages.
Unless you have a 830nm (Deep Black IR) conversion, chances are that your images will have red to orange-looking skies, like this:
In order to make the sky look blue, we need to radically shift the color hues in the image. Unfortunately, most RAW editors (including ACR/Lightroom and Aperture) do not permit a global hue adjustment of the magnitude required to shift red to blue and vice-versa. One exception to this is Nikon’s Capture NX2, which can be used with good results on Nikon NEF images (more on this later).
Method #1: RGB Channel-Swapping
The first way to create the “blue-sky” look is to do something called RGB Channel-swapping. This technique changes the red channel to blue, and the blue channel to red. You can then adjust hues to taste.To do this, you’ll need a version of Adobe Photoshop. After you open your image, go to Image–> Adjustments –> Channel Mixer. In the channel pull-down menu, start by selecting the Red channel. Set the values as follows:
- Red: 0%
- Green: 0%
- Blue: 100%
Then select the Blue output channel and make the following adjustments:
- Red: 100%
- Green: 0%
- Blue: 0%
Once you’ve done this adjustment, you can save the values as a preset to quickly apply later on other images. After swapping the channels, you may need to perform a hue/saturation adjustment to get the colors to your liking.
Advanced Method: Lab Channel Swapping
If you have Photoshop, you can also do a red-blue channel swap using Lab color mode. This sometimes produces a nicer result than RGB channel-swapping. Blues tend to be slightly less intense. To perform this adjustment, you’ll need to first change your image from RGB mode to Lab color mode. Choose Image–> Mode –> Lab Color. If you have layers in your image, you may be prompted to flatten them. Don’t. Next, open the Curves tool. The two color channels are called “a” and “b.” All you need to do here is invert the linear curves for both the a and b channels, like so:
Once you’ve made this adjustment, you can go back to RGB color mode by choosing Image –> Mode –> RGB Color. Again, don’t flatten any layers if prompted to do so.
What if you don’t have Photoshop?
If you don’t have an editor that allows for channel mixing, then an alternative adjustment is to perform a 180° Hue Shift. While not as powerful as channel-swapping, you can get results that are pretty close in most cases. You can perform a 180° hue shift with Photoshop Elements, Viveza 2, and Nikon’s Capture NX2. All of these applications work with TIFF and JPEG images. In the case of Capture NX2, you can work directly on Nikon NEF (RAW) files.
Open your image, and choose Enhance –> Adjust Color –> Adjust Hue/Saturation. Set the Hue slider to 180°. Then adjust saturation to your liking.
Nik Software Viveza 2
Nik Software’s Viveza 2 (Part of the Nik Collection by Google) has several interesting features, the most interesting of course is local adjustments via Control Points. However, you can also use Viveza 2 to perform global hue and saturation adjustments. You can also use Viveza 2 directly from Lightroom or Aperture if you don’t have Photoshop. Launch Viveza 2 and then set the global Hue Slider to 180°. From there, you can adjust saturation and other parameters to fine-tune your image.
Nikon’s Capture NX2
If you shoot with a Nikon camera and capture NEF images, you can use Capture NX2 directly on your RAW files. You can also use Capture NX2 on TIFF/JPEG images exported from Lightroom or Aperture if you wish. To perform the hue adjustment, you’ll need to add a LCH Editor Adjustment Step. Then, choose “Hue” from the drop-down menu in the LCH Editor window. Set the Hue range to 180° and then drag the slider (triangle) up or down to get the effect.
At the end of the day, you can find lots of ways to be creative with your infrared images. The blue-sky effect works well when you want to have an image that combines realistic elements with surreal ones. There is no single correct method for creating this effect. Sometimes, you’ll find certain images work better with one technique than others. Keep exploring and enjoy the ride!