Converting to Mono (Black and White)

This tutorial uses PhotoShop CS2

As the old saying goes There's more than one way to skin a cat and there's more than one way to convert a colour image to monochrome. Which method you choose is up to you, they all produce different effects, some you will like, others you won.

Before digital imagery it was possible to produce different effects with Black and White by using colour filters. Orange and red filters would darken blue skies and render clouds more dramatically than they appeared to the human eye. Processing techniques could increase contrast and even the effective speed of the film. There are a few cameras on the market that will take the image in Black and White, However, with computer technology, there is really no need, it can all be done after the image has been captured.

Although one can simply de-saturate the image, the techniques are a little more sophisticated if you want to produce professional looking images. Converting a digital colour image to monochrome works on a similar principle as using colour filters on the front of the camera, it is the element of control over how different colours are treated that separates one technique from another. In this tutorial first tutorial I will explore the Lightness Channel.

Lightness Channel conversion

When converting to monochrome we are more concerned with the luminance of the image rather than its colour. Luminance is just a posh way of describing the distribution of the image brightness. Obviously we are no longer relying on the colour to produce impact, we are now only dealing with light and dark and the distribution and level of shadows and highlights, and of course the gray tones between each. So let's open an image in PhotoShop and get on with it.

As we do not need to work with a large image you can use this one as it is by right clicking and saving it on your own computer. You can of course use your own image. Go to the channels palette, if you can’t see it go to window and click on channels. What you see in the channels palette is the Red, Green and Blue channels, along with the RGB (all colours) at the top. Now go to the top menu, click on Image – Mode – Lab Colour.

You will not see any changes in the image at this stage, but the channels have changed, as you should see in the channels palette. The luminosity has been separated from the colour. The part of the image we will be dealing with is the lightness channel. If you click on that layer in the palette you will see the monochrome image. At this stage only the lightness channel should be highlighted in the palette and your image should appear as Black and White.

.

Now go to image – mode and chose grayscale. When asked to discard other channels click OK

You should just have the gray channel left. Click back to the layers palette. We now need to duplicate the layer. Hold down Ctrl and press the J key. This will create a layer above the Background layer.

Making sure the duplicated layer is highlighted. Right click on the layer and chose blending options. Change the blend mode to multiply. This will darken the image considerably, don’t worry about that because we are going to change it.

Now we can alter the luminosity of the image and create you finished image. Still with that layer highlighted, reduce the opacity until you are happy with the quality of the image. I have reduced mine to 30% but it is a matter of taste and judgment.

The two images below show the result from just converting to grayscale and the lightness method, which gives more control over the tonal range.

Conversion using Grayscale mode

Conversion using Lightness Channel