Converting to Black & White using the Channel Mixer in Photoshop

May 20, 2009 by Jennifer Farley    3 Comments    Posted under: Blog

There are many ways to convert an image to black and white in Photoshop. In the past I’ve written about the Desaturation Adjustment Layer and also converting using Calculations (not as hard and mathematical as it might sound!). Today, I’m taking a look at a method which will produce really nice, dynamic black and white photographs. The method in question uses an adjustment layer and the channel mixer, and it’s really easy.

The Channel Mixer adjustment layer first appeared in Photoshop 5, so unless you have a VERY old version of Photoshop you will be able to convert your images with this technique.

1. Open your colour image in Photoshop.

2. Click on the Create New Adjustment Layer icon at the bottom of the Layers palette.

3. From the pop-up menu choose Channel Mixer. The Channel Mixer dialog box opens and you’ll see lots of sliders to play with!

4. Check the Monochrome box at the bottom left corner and your image will immediately be converted to black and white.

By default, when you hit the monochrome checkbox, the Red channel is set to 40%, the Green to 40% and Blue Channel is set to 20%. Most of the time, the conversion will not be the stunning black and white you want it to be, so this where we use those sliders to make our own adjustments.

In theory, many Photoshop instructors reckon that the percentage values on the sliders should add up to 100%, but the fact is, every image is different and if the numbers don’t add up on the sliders but the print looks great, what difference does it make.

6. To give the image some extra contrast, a formula that works well (devised by Photoshop master Scott Kelby) is to set the Red channel to about 75%, set the Green and Blue channels to 0% and consider this your starting point. Now drag the Green and Blue sliders to the right. You’ll see a dramatic change in the image as you drag to the right and will create a lot of extra contrast. If the highlights on the image start to look very blown out (i.e. very white), then drag the Green and Blue sliders back to the left.

The other slider to look at here is the Constant slider. This adjusts the overall brightness. In this example, I darkened the whole image down by dragging the Constant slider to the left, to a value of 5%.

When you’re happy with how your image looks click OK. You can see the values I used for this photograph below.

The best thing about working with an adjustment layer is that you’re not changing or harming ANY pixels in your image. A new layer is created and the adjustments are applied through a mask.

If you want to go back and change your black and white conversion, simply double-click on the Channel Mixer thumbnail (3 circles) on the adjustment layer and the dialog box will open again.

And that’s it! Here’s my before and after images;

Got anything to say? Go ahead and leave a comment!