One of Photoshop’s strengths (and, some would say, its weaknesses) is that there are usually various ways to achieve any given task. Black and white conversion is no exception, and in this post I’m going to show you a technique I often use to get quick, punchy black and white shots. It’s called the Calculations tool, and it works by taking two user-specified colour channels and blending them using a layer blending mode. It’s fast, simple, and gives good contrasty results.
Start by loading up the colour shot you want to convert. Then simply click Image > Calculations. You are presented with the following dialog box:
Here you can choose the two colour channels you want to blend, and the mode you want to blend them with. What you choose here depends on what results you want.
A good starting point is to set one channel to Red, another to Green, and the blend mode to Overlay. Boom, instant punchy black and white! You can change the channels selected to see what effect they have: experiment. The modes i use most are overlay, soft light and multiply. Overlay and soft light give very punchy results, with strong blacks and whites, while using multiply with both channels set to Red gives great dramatic dark skies. You can change the opacity of the blend underneath the blend mode dropdown, which alters the strength of the effect. Once you have decided on the settings you want, change the last dropdown from New Channel to New Document and click OK.
You now have a new black and white image. You will note, however, that the image mode is set to ‘Alpha’. Before you can edit the image in any useful way, you first need to convert this to RGB. To do this, click Image > Mode > RGB. You can now edit the image as you would any other.
You can, of course, perform the Calculations command multiple times on the same colour image using different settings. In the image below, I converted the colour original once using a Red/Green Overlay calculation to get the foreground, and then again with Red/Red Multiply to get the sky, and then blended the two shots using the technique detailed in this post.
Next time you want to convert a shot to black and white, give Calculations a try, and let us know how you get on.