Infrared (IR) Photography – Part 2: Post Processing
Last month my eTip was on getting started with Infrared (IR) photography (see http://www.photocheatsheets.com/eTips.aspx?et=102). This month's eTip is on how to Post Process infrared images.
Infrared images are very different than visible-light images, and some JPEG images need to be post-processed. The filters that alllow infrared light to pass will create an image that has a red/purple cast to it. It will look horrible - until post-processed.
It's not hard - just different.
I will be using Photoshop for post-processing - other programs will be similar.
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Discounts!
In order to shoot infrared, you need a camera capable of seeing infrared. Any digital camera can see IR, but the sensors in our cameras have been modified by the manufacturer to block out infrared. So, a simple conversion is needed. We have partnered with KolariVision to provide discounted conversions and accessories. Use the code PhotoBert in the cart for a $10 discount. Click here for more info.
You can also purchase a camera that's already been converted - it's the easiest way to get into IR photography! (Don't forget to use the code PhotoBert in the cart for a $10 discount!)
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White Balance
When shooting JPEG images, it's critical to get the white balance right. Some cameras are capable of setting a custom white balance correctly, but some aren't. If you have one of the cameras that can't, you'll need to do some post-processing to get the white balance correct.
You'll always have to correct the white balance with RAW images.
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What does a RAW (or JPEG where the white balance wasn't set properly) Infrared image look like straight out of the camera?
In a word - Bad! The image to the right is a RAW image straight out of the camera. The JPEG image looked the same, as a custom white balance wasn't set. Both have a red cast over the entire image. This is because the infrared filter - either covering the sensor or in front of the lens - has a red-tint and only lets infrared light pass through.
Note: Some cameras can provide a correct infrared white balance for pure JPEG IR images (850nm) where a custom white balance was set. if your camera can do this, then post-processing may not be needed. Other cameras will require post-processing.
It takes just two adjustments to correct this.
First, the white balance needs to be adjusted. This will make it look (almost) like a grayscale image.
Second, a channel swap needs to take place, swapping the red and blue channels. This is easier than it sounds, and, if using Photoshop, you can download a free set of "actions" to do this in a single mouse-click. (see https://kolarivision.com/post-infrared-photo-editing/false-color-action-suite-for-photoshop/?ref=54)
OK, let's get started. |  |
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Step One
The first step is to correct the white balance. Most post-processing programs don't have the white balance adjustment range to correct the white balance for an infrared image, so you need to do it in 2 steps.
First, in Adobe Camera Raw (ACR), set the color temp and tint all the way to the left, as in the image to the right. This is the maximum white balance adjustment that ACR is capable of. Then open the image in Photoshop.
We'll complete the adjustment in the next step.
| (Click for a larger image)
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Step Two
You'll need to go back into ACR. In Photoshop, you do this by going to the Filter menu and selecting Camera RAW Filter. Once back in ACR, use the white-balance dropper to click on a white area (grass or foliage usually works best). This should set the white balance properly. (see the image to the right)
Note: there's another way to get the white balance correct, and that is to use a custom profile in Photoshop. I'm not going to get into that right now, but if you Google adobe profile editor infrared, you'll find a number of sites that describe how this is done. | (Click for a larger image)
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Step Three
This step is only required for false-color images - those shot between 550nm and 720nm - it's not required for pure IR images (850nm).
Next, you need to do a "channel swap" between the red and blue channels. This requires a few steps, but can be easily automated with a free action from Kolarivision.
(see https://kolarivision.com/post-infrared-photo-editing/false-color-action-suite-for-photoshop/)
To do the channel swap manually in Photoshop, select from the menu:
Image | Adjustments | Channel Mixer
Then select the RED Output Channel and set the Red value to 0 (from 100) and the Blue value to 100 (from 0).
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Then select the BLUE Output Channel and set the Red value to 100 (from 0) and the Blue value to 0 (from 1000).
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This should correct the colors in your image. You can then tweak whatever settings you feel are necessary (levels, brighness, contrast, etc.).
We went from a red-cast to a beautiful false-color image.
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Summary
Post Processing is required for most images. If you're accustomed to post-processing your images, you'll find this pretty simple - just a couple of extra steps. |
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