"I'm shooting infrared. My main output is RAW files, and any JPGs are just aides memoire. Between my raw processor and Photoshop I'm going to do some fancy channel mixing to either add false colour, or take it away entirely and generate a monochrome image. So I'm assuming my white balance doesn't matter. Is that right?"
Nope, and this explains why.
In normal visible spectrum photography, most of the time, white balance is seen as "getting the colours to look right". In an infrared image there are no true colours, but ironically checking or fixing the white balance is still a critical first step in developing the image.
If you've bought or had a camera converted to infrared it should have been set up with an appropriate custom white balance, and things should run smoothly, but it's relatively easy for things to go awry. You may add additional filters, throwing the white balance off, you might accidentally upset the settings, or you might receive a camera which has not be correctly set. In any of these cases you need to understand the objective for the white balance, and how to fix it.
Have a look at the rogue's gallery above. These were taken one after the other on my converted Panasonic GX7, and are shown as they open in Capture One. Clockwise from top left:
Not only are the bottom two a bit difficult to "parse" visually, but there's a more significant problem, which reveals itself from the histogram, which looks like this:
The "red" channel is overexposed, and the others have almost no information. If we try converting these images to black and white with the channel mixer, starting here, we find that the red slider is almost like a switch on the whole image, the yellow slider makes a small difference to the breaking waves, and the others might as well not exist.
This is the real importance of setting the white balance. It takes the available colour information (basically a bunch of reds) and re-aligns it with the visible colours, so that each frequency range can then be visualised, and manipulated by tools which work on a visible colour range. In the process, the information in any "overloaded" channels is spread out, and this will fix a lot of mild overexposure problems.
How do you rectify a problem image? Fortunately there are a few ways to fix these problems, even after shooting:
Applying the above to the bottom left image gets an image where the red, yellow, blue and cyan channels all affect distinct elements, and I can mix to an image with a decent overall histogram, dark rocks and sparkling highlights, as I wanted:
So don't ignore your infrared images' white balance, but if it all looks a bit weird, don't panic, either!
© Questa Computing Ltd. 2007-2011
Page last updated 06 July, 2017 09:04