Converting Color to B&W in Photoshop

When you’re taking pictures you may see, in your mind’s eye anyway, the scene as a stunning black and white image. You know that is how it will be printed, so how do you make the picture?

Some cameras will have a setting/button/mode etc., that instructs the camera to produce black and white images, and what you will get is a 16-bit grayscale image. For many applications that will be fine. But if you start with a distinct personal vision of the image, you will often find the result to be disappointing, and almost impossible to change.

Besides the fact that you probably don’t know where the stupid setting is in the first place, and you don’t want to spend time finding out, the in-camera B&W image is produced in the camera’s computer using an algorithm – usually it’s a simple desaturation. Desaturation consists of interpreting each of three colors in the sensor image as a grayscale, and combining them according to some averaging technique. The output is a single channel grayscale image; two-thirds of the image data your camera captured in the first place is gone and cannot be recovered. Worse, it is unlikely that the image looks like what you imagined in the first place. You can do much better in Photoshop.

By capturing the image in color and processing in Photoshop, you can control the tonality of an image in many different ways to achieve results more in line with what you’d imagined in the first place.

I can think of several ways you can convert a color image to b&w in Photoshop. Each method offers different controls, and creates a distinct style of output.

Lets start with the simplest.

Desaturation

Your camera uses some variant of desaturation to produce monochrome output. You can do that in Photoshop as well. Image → Adjustments → Desaturate will do it. Here is the resulting image.

As you can see, the converted image is somewhat muddy; looking at you could not tell that the season was fall and the Cottonwoods a clear yellow. Also, the light-colored soils don’t show up that way and the sky is a bit anemic. We can do better.

Channel Mixer

The Channel Mixer is one of the oldest processes in Photoshop that you can use to do this conversion. Its default conversion process is pretty good and you can control what percentage each of the red/green/blue channels contribute to the finished conversion. It also has several presets that produce good images. I have used the red preset many times in the past.

In the default conversion, the result is somewhat better. Noticeably, the yellow trees in the creek are rendered in a slightly lighter tone and look a little more realistic. Also, the sky is a bit more lively.

Although a great deal of control is possible with the channel mixer, it has one major drawback – it requires you to think and work in the additive RGB color space. Very few people find this to be a very comfortable way to work. For example, in RGB, Yellow is an equal mixture of Red and Green. To control the brightness of yellow objects you must manipulate the Red and Green channels together, and in lockstep. Not very intuitive.

Black and White Adjustment Layer

The Black and White Adjustment tool does not appear in your Adjustments Palette as you might expect but is implemented as a special type of Layer. Use Layer → New Adjustment Layer → Black and White to invoke it. This adjustment layer is a marked improvement over the Channel Mixer layer. It allows you to adjust the brightness of 6 different colors (as opposed to the three colors available in the channel mixer), and has 12 different presets. If you like you can choose a preset that looks close to what you had in mind and then tweak the tones to your liking. Also, the default conversion is slightly better than the Channel Mixer’s.

If the adjustment icon does not appear on your copy of photoshop use the
Windows → Adjustments command to bring up the palette.


Here is the default conversion.

In this conversion different tones are acceptably separated.

Because this tool allows you to adjust the brightness of colors as you see them it is much easier for photographers to use. In the following image I used the B&W Layer Adjustment: I increased the relative brightness of Yellow to bring out the trees, and I decreased Blue to make the sky more dramatic.

As you can see, the trees now stand out like they did in the color image, and the sky is much more dramatic. (I’ve exaggerated the changes to make them more visible on your screen.)

Gradient Mask

The Gradient Mask might seem like an odd way to convert images to black and white. It is usually used to add color to black and white images. But it works and does an excellent job at that. To use it click the Black and White icon in your Adjustments palette.

Choose the Foreground-to-Background gradient if it appears in the presets, or simply define the gradient yourself. You should have a gradient bar that starts black and fades to white on the right.

Adding the gradient to a color image instantly converts it to black & white.

As you can see, this conversion is very good, right out of the box. It’s only drawback is that once done, it’s done. You can change the gradient in the gradient editor, but doing so requires that you think in computer software terms rather than human ones.

Black and White Adjustment Plus Gradient Map

By combining a Black and White Adjustment layer with the Gradient Mask adjustment, you can have the best of both worlds. Do the Black and White Adjustment first. Then add the Black and White Gradient Mask layer above it. Here are the default results.

In this result, the contrast is improved without reducing mid-tone separation. By using these two adjustments together you gain a huge amount of control over the final product, control that is both easy to use and powerful.

I used these two tools together for the final image. Starting from the default, I made three small changes: (1) I brightened yellow a bit to bring out the fall color of the trees. (2) I darkened the blues slightly to make the sky more dramatic. (3) Finally I moved the mid-point of the gradient slightly to the dark side to brighten the image a bit. Here is the result.

Now this is what I had in mind when I started! The result, as you can see, is a huge improvement over simply desaturating the image, and takes very little effort to implement.

I hope you find this a useful addition to your bag-o-tricks for Photoshop editing.

 

About aneyefortexas

Retired writer/teacher/photographer, now photographing the Chihuahuan Desert at the Big Bend Ranch State Park, Texas.
This entry was posted in Photography, Photoshop and tagged , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s