I’ve seen some pretty poorly-corrected photos lately. I’m going to show you how to use the channel mixer tool to colour-correct your photos, since I find it gives the greatest level of control.

Here’s a my boyfriend holding up a bunch of fake Oscar trophies at an Oscars party we went to, because he’s awesome and also a lovable wiener:

You’ll notice that the photo’s quite yellow — and it shouldn’t be that yellow.

The thing about cameras is that although they pick up light and colour roughly the same as our eyes, they don’t have the internal colour-correction system that our brain provides. Just like how our eyes adjust for high and low levels of light, they also adjust for colour.

This is why your house might look dark and greenish the moment you step in after being out on a bright, sunny day, and it’s also why if you stare at a bright red spot for thirty seconds, then look at a blank wall, you’ll see a cyan “ghost image.” Your brain has been compensating for the intensity of the red by adding cyan.

Incandescent light is extremely yellow. It’s comfortable and warm in a house (this is why the new fluorescent eco-lights come in a tinted yellow variety), but looks terrible in a photograph. This is why proper colour adjustment is important — you want the photo to look the way it did to the photographer’s naked eye.

I’m going to open up this photo in photoshop, and create a channel mixer adjustment layer. This particular adjustment allows me to increase or decrease the levels of a particular colour within other colours.

I know that sounds confusing, so the way I remember it is, if I’ve got the red channel selected and I slide the blue slider to +12, I’m adding more red to the blue. All the blue parts of the image will have 12 added to the red value. If it’s a solid block of blue (0 red, 0 green, 255 blue) it will suddenly become (12 red, 0 green, 255 blue), and have a slight purplish hue.

Since this is yellow, incandescent light I’m dealing with, I’m going to open up the blue channel (blue is the opposite of yellow). If the light was too yellow, I’d have to adjust both the green and blue channel (green + blue = cyan, which is the opposite of red). If the light was too blue, I’d adjust the red and green channels, and so on and so forth.

I’m just going to nudge them. A teeny bit. Add 12 blue to both the red and green sliders.

Now, this is good — but it’s a little purple. What’s the opposite of purple (well, magenta, really)? Green! I’ll put…oh, maybe +7 in the blue slider, and 5 in the red slider. That looks about right.

Really, there’s no “proper value” to add; it all depends on the photo. Eventually you’ll get good at eyeballing it, but just make sure your monitor is calibrated properly. If you’re really, really unsure, you could compare the flesh tones to a flesh tone guide, or to professional photographs.

And remember, first and foremost, coloured light isn’t all bad. Sometimes, it’s better to exaggerate the colour of light or change it to another colour entirely. Some photos will look completely amazing with pink or blue or green light, and boring with white light. Use your judgment!

Personally, I think I should create a selective colour layer and tweak certain colours (yellow and cyan) so they’re a little more prominent. Here’s my final result:

Like this tutorial? Here’s some more.