Who needs a Channel Mixer? Try Hue/Saturation adjustment layers instead

There are countless different ways of converting color images into black and white, but Photoshop’s Channel Mixer is one of the most popular because it can change the tonal relationships between colors, making some come out darker in the black and white conversion, and some lighter.

The problem with the Channel Mixer is that it’s not terribly intuitive from a photographer’s point of view, and its adjustments are crude. You can darken blues and lighten reds, for example, but these color ranges are pre-defined, and might not produce the optimum results for the photo you’re working on.

Photoshop has a more advanced black and white conversion tool that splits images up into a larger number of colors and will also maintain the overall image brightness as you adjust them. But the number of sliders does make it pretty complicated to use.

Original: Here’s the color photo we want to convert into black and white.

Step 1: Simply desaturating the image produces a rather lackluster result.

Step 2: But a clever combination of Hue/Saturation layers produces
a dramatic improvement.

So here’s an alternative approach that works with both Photoshop and Elements, and offers rather more control over the outcome. It might look complicated initially because it uses two separate adjustment layers, but the principle is actually quite straightforward once you remember that the two layers work just like the Channel Mixer but split the job into two parts.

There are some good reasons for doing it this way, especially if you’re using Elements. For one, the only alternative is the Convert to Black and White tool (it’s the Channel Mixer in disguise) and Elements doesn’t let you apply it as an adjustment layer.

You can use this Hue/Saturation layer technique to target colors much more accurately, but it doesn’t stop there. You can then use a third Hue/Saturation layer to boost the contrast or apply a toning effect.

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Alternative Channel Mixing Explained

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  Desaturating the Image

  Create a black and white photo conversion with a Hue/Saturation adjustment layer and drag the Saturation slider all the way down to zero. The results aren’t particularly good because the colors in the original aren’t very well separated, but that doesn’t matter…

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  Create Another Layer

  Create a Hue/Saturation layer below the first, and use this to modify the colors. This is taking the place of Photoshop’s Channel Mixer. To darken blue skies, for example, open the pop-up menu in the Hue/Saturation dialog and swap from Master (the default) to Blues...

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  Adjust the Lightness

  With the Blues selected, drag the Lightness value down to zero. You should see the sky in the picture darken, while the rest of the colors are unchanged. Note, the ‘top’ Hue/Saturation layer acts on the black and white conversion; colors change via the layer below.

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  Using the Eyedropper

  This adjustment will darken blues in general, but might not target the precise shade of blue in your picture. Select the Eyedropper tool in the Hue/Saturation dialog and click on an area of blue sky. The color range will be adjusted to match the color you’ve clicked on.

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  Adjust the Color Range

  At the bottom of the Hue/Saturation dialog sit markers indicating the color range that’s selected; you can click and drag between the markers to shift it. If you see noise in the sky, adjustments can reduce it, though the darkening will be reduced too. Experiment.

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  Making Reds Brighter

  You can use the trick to lighten other tones. To simulate the effect of a red filter, select Reds in the Hue/Saturation dialog, then push the Lightness slider to its maximum. Again, use the Eyedropper to click on an area of the picture to make the range more precise.

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  Increasing the Contrast

  The two Hue/Saturation layers work together to simulate the effect of the Channel Mixer, but you’ll often find that images need more contrast when they’re converted to black and white; for this, use a third Hue/Saturation layer. Set its Blend Mode to Soft Light.

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  Mask Contrast Increases

  There may be areas of the picture which have become too dark or too light. That’s easy to fix, though. First, select the adjustment layer’s mask, then choose a large, soft brush, set the color to black and paint over the areas you want to protect.

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  Quick Tip

  The contrast-increasing adjustment layer at the end of our walkthrough can also be used to tone the picture. Double-click the adjustment layer’s icon, check the Colorize box and choose the color tone by dragging the Hue slider.

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