Converting to Black & White using the Channel Mixer

When converting pictures to Black & White in Photoshop many people, including me in the past, would just select image->mode->grayscale, job done. The result was usually a bit lacking in contrast but a tweak with a curve layer would soon fix that.

Then I came across a better way of doing things with far more control using 'channels'. There is a bit more work involved but the difference in the result can be huge.

I have chosen the picture on the left, not because I foresee a massive demand for black & white pictures of spaghetti, but because the colors are similar to those you would find in skin tones. And what do we photograph more than anything else? People.

Below left is the result of just changing the mode to grayscale, as you can see it's a bit washed out and lacking in detail compared to the picture on the right that has been created using the channel mixer.

If you are not familiar with channels you'll find the channels palette under the 'window' menu. There are three channels, one each for red, green and blue, and an RGB view, which is the one we normally see. Think of these channels as the three layers on a color film, each represents the amount of it's color (red, blue and green) in the final image. Another way to look at it is that it represents a black & white image taken through a filter so that only it's color reached the film.

As a general rule of thumb, we want black & white images to be a bit more contrasty than their color equivalents. The image above left is probably an accurate conversion from the color but the one on the right is more satisfying.

Below are the three channels and the composite of this image. The first step in this procedure is to open the channels palette and have a look at each of the channels in turn. You can see that the red channel is almost over exposed on the spaghetti and would not make a very satisfactory b&w image. The spaghetti in the green channel is not a million miles from the image we got from changing the mode, and the blue channel contains a lot of detail but is a bit too dark and contrasty on it's own. Look at the fork in each of the three images and you can se that, because it is a neutral color, it appears to be more or less the same in all three channels.

When you first open it the red channel will be at 100% and the other two will be at 0%, and the image will still be in color The first thing to do is tick the monochrome box at the bottom to see your image in b&w.

Then adjust the sliders until your image is the way you want it. The permutations are endless as you can see but you need to aim for a total from all three channels of more or less 100%.

If you go over 100% the image will be a bit brighter and less than 100% will darken the image a little.