Tips and tricks to keep in mind when converting your images to black and white

When most people think about black and white photos, the first subject that comes to mind is people. Portraits can benefit greatly from the mood provided by grayscale images, but one can only agree that black and white landscapes can be at least as magical as colorful ones when looking at some of the photos made by, for instance, Ansel Adams.

At the moment of pressing the shutter, though, it is always a good idea to shoot in color and only turn your images into black and white during post-processing. The obvious reason for this is that, once you are at home, having the color image you can always decide to keep it that way if, for any reason, you don’t like the way your image looks in black and white.

The other reason is that converting an image to black and white can involve much more than simply reducing the saturation of all colors at once.

Take for instance the following image of the skyline of Atlanta, USA.

There are two straightforward ways to convert an image to black and white in Photoshop. The first one is to bring the saturation to a minimum by means of a ‘Hue/Saturation’ adjustment layer. The image below shows the result of this process.

In general, we already have our grayscale image. We could already start to make the final adjustments to make our image look the way we want but, as you will see next, we are missing invaluable information that can help us make local enhancements while making the conversion.

Now let’s remove the ‘Hue/Saturation’ layer and create a ‘Black and White’ one instead. As you can see in the following image, the newly created adjustment layers (inside the red rectangle) contains several sliders, each corresponding to a different color (Reds, Yellows, Greens, Cyans, Blues and Magentas).

What these sliders will allow us to do is control the luminosity of the areas with the matching colors in the original image. This provides an incredibly easy way to enhance the contrast of the image on a local scale without having to undergo complex selection processes. For the following image, I increased the value of the ‘Greens’ and ‘Yellows’ sliders to enhance the trees and the field (including the yellow letters) and decreased that of the ‘Cyans’ and ‘Blues’ to darken the sky in order to produce more contrast.

This last point is a very important one to keep in mind when editing grayscale images. The fact that you are not including colors in your photo anymore means that your image can have a rather flat look and this has to be counteracted by carefully adjusting the contrast. Actually, pushing the contrast much farther than you would normally due when dealing with a color image will normally produce much better results.

However, increasing the contrast tends to produce dark images and that is why it is a good idea to always make contrast adjustments together with brightness adjustments. For this, simply create a ‘Brightness/Contrast’ layer and alternatively move both sliders until you are happy with the result.

Since we are pushing both the brightness and contrast to relatively high values, you can see that some parts of the image will get degraded. The bright areas will tend to look overexposed due to the increased brightness and the dark areas will look noisy due to the increased contrast. Don’t worry about that right now. Simply focus on the regions with intermediate brightness (the trees and houses in our image).

Now you can simply mask the areas that got degraded by painting with a black ‘Brush Tool’ over the layer mask that is created along with the adjustment layer. This will depend on the particular image you are working with, but I find that an opacity of about 20 to 30 % tends to work well and gives you more control than using a larger value.

Another advantage of keeping the color information while capturing your images is that you can also play with selective color, which is nothing more than converting your image to black and white while keeping specific colors in specific regions.

For instance, let’s turn our image into black and white and keep the yellow tones of the letters in the stadium and the roof of the skyscraper on the left. To do this, we take our color image and create a ‘Hue/Saturation’ adjustment layer, where we completely desaturate all the colors but the one we want to keep.

Next, we create another ‘Hue/Saturation’ layer and bring the saturation to a minimum while on the ‘Master’ channel. This will of course create a completely black and white image. To recover the yellow in the areas we want, we simply mask out the adjustment layer by painting with a black brush with a 100 % opacity. Since all the surrounding areas were already converted to black and white with the previous adjustment layer, we don’t even need to be precise when using the brush tool.

And that’s it. With a few steps, you can keep the color you want in any area of your image while converting the rest of the image to grayscale. The truth is that some people love and some people hate selective color and, from my experience, it can work out pretty well in some cases creating interesting images and it can also produce some ugly results when over-used, but in any case it makes sense to try it and you might be gladly surprised with the final results!