Going to show you what white balance multipliers are for, in any software…
First, let’s look at a normal raw development. Showing you this in rawproc, my hack software, because the processing pipeline is laid out for you to see and I can arbitrarily turn on/off any operation:
Rather normal color and tone, no? Okay, take a look at the upper left pane, this is where the toolchain is listed and managed. These operations are applied to the raw data in order from top to bottom. Note that the last tool, the tone curve is checked, that’s the tool whose results are displayed in the main pane. The selected tool, the one with the white background, has its parameters displayed in the bottom left pane. I’ve selected white balance for this because I’m now going to turn it off by unchecking the box in the top left of the parameters pane:
Same processing, just without white balance. THAT is what you’re correcting with those multipliers. Note the histograms of the two screenshots; the first one’s right-hand peaks are pretty well aligned, and the second one’s are not. This works for most but not all images: adjusting the white balance multipliers so those peaks line up is one way to get a decent white balance.
I picked my Nikon D7000 for this illustration, because the effect is quite apparent. Each camera has their own characteristic spectral response, and it’s that “un-evenness” that needs correction. Here’s a plot of the D7000 spectral response:
Note that the so-called “red” channel is deficient in energy relative to the others; that’s why the white balance RGB multiplers for this image, 2.097656,1.000000,1.316406, has such a heavy hand in the first number.
You asked…