Why Does Duotoning Work?

I’ve never been big on duotone – it seemed like a gimmick. But recently I had an insight into its real power.

Here’s what I used to think: “sepia” is just a one-click way to add fake nostalgia to a photo. Teal-and-gold is a millennial fashion photography cliche. It’s all been done to death, like selective color.

But here’s a photo I did recently, with the intent of black-and-white:

Black and white photograph of a tall dead tree.

I was happy with it – and I’d spent time getting it, making a couple of trips into a marshy area where an expanding wetland had drowned a lot of trees. I liked the way this dead giant reached crazily into the sky, warning of doom – or maybe offering wisdom like one of Tolkien’s Ents. It was December and the low, dim sun set off the looming tree. But the tree, being backlit, didn’t seem to quite step forward in the photo. I’d selectively brightened it and dialed up its contrast somewhat; but you can only push that so far before it looks overprocessed.

But when I fiddled with the “Split Toning” and added a bit of sepia to the hightlights, I was surprised at how the photo came to life:

Photgraph with sepia toning - a dutone.

Why did that work? To my eye, mostly because the sky behind the tree “felt” brighter, as did the highlights in the bark. But they aren’t really brighter, and that was my insight: duotone adds a color gradient from dark to light, that parallels and subjectively reinforces the luminance gradient. You feel like the photo is brighter and has more contrast. But the luminance histogram hasn’t changed; you’re just feeling the effect of color. Put another way, you’ve reinforced the luminance gradient with a color gradient.

The effect is even stronger if you also add blue in the shadows, as in this version:

Photograph processed as a duotone.

I like the first version; blues feel artificial in this organic subject.

I’ve used the “split toning” tools in Lightroom and Capture One. And there’s a way to do it in Photoshop Elements with gradients, masks, transparency, luminance – way too complicated. But Exposure X6 has the best tool by far:

In a nutshell, you choose shadow and highlight colors, set their strengths, and use the sliders to control how far “up” or “down” you want the colors to extend, from the respective ends of the histogram “in” towards the center. That’s the cool part – with some fiddling, you can set the transition to coincide with the point in your photo’s histogram where you want highlights to start being accented. There’s no formula, you just experiment until the emphasis lands on the areas of the photo where you feel it belongs.

When applied like this – with intention – duotone can really add something positive.

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