Photoshop’s Black & White and Channel Mixer commands are powerful methods for converting the color photos (that nearly all digital cameras are hard-wired to produce) into rich monochrome images. You can then take those images several steps further by colorizing them to produce extraordinary duotones and polychromes. In this tip, we’ll look at these commands, as well as other ways to create black-and-white and faux-color images in Photohshop.

Today’s tip comes from Chapter 18, “Black &White and Colorize,” part of Deke’s video course Photoshop CS5 One-on-One: Advanced on lynda.com.

The term “black & white image” actually means many things. Some are simple “grayscale” images while others are dramatic reinterpretations of the hues and tones in a color scene, all based purely on black, white, and neutral shades of gray. Beyond those neutral black & white images are various toned images that use color in different ways. These can be monochromatic (the same hue at differing saturation and luminance levels), duotone, or polychromatic images that we still tend to refer to as “black & white,” but they’re actually color images.

When it comes to creating black & white images, your camera’s built-in black & white conversion options pale in comparison to Photoshop’s array of methods. It’s no accident that I used the word conversion; your digital camera always starts out recording images in color, even if you use one of its black & white settings. If you’re shooting JPEG, the result is a grayscale image with no color information. But, if you’re shooting RAW, it still contains all of its color information—its develop settings have simply been preset to render a black & white image. Once you open a RAW image in Camera Raw or Lightroom, you could revise the black & white conversion settings, but you’ll have even more control if you simply shoot in color and convert in Photoshop.

Simple Conversions

One of the simplest methods of converting to black & white is to select Image > Mode > Grayscale from the menu bar.

If your file contains layers, you’ll see a dialog asking if you want to flatten your file. For this method of conversion, go ahead and flatten. We’ll discuss less destructive methods soon.

You’ll see a confirmation dialog asking if you want to discard the color information. If you say yes, the result is a file in grayscale mode with only one channel. This grayscale conversion works by blending the contents of the Red, Green, and Blue channels in specific proportions.

A second approach is to take advantage of the ways color is encoded into the image via the Red, Greeen, and Blue channels. Each channel will have a different appearance, and you can easily convert any channel into a grayscale image.

1. Switch to the Channels panel
2. Click on each channel to review its appearance.

One pitfall is the option to show channels in color. When this option is active, the Red, Green, and Blue channels are tinted in the Channels panel,  and so are the previews in the editing area. Select Edit > Preferences > Interface (Mac: Photoshop > Preferences > Interface) and un-check “Show Channels in Color” in the General section at the top of the dialog. Click OK to dismiss the dialog.

3. Select the channel you like best and select Image > Mode > Grayscale from the menu bar.
4. You’ll see a dialog confirming that you want to discard the other channels.  Click OK.

If you’re bored with the “Discard other channels” alerts, you can check “Don’t show again” before you click Yes to avoid seeing them in the future.

Multiple Black & White Versions within

In the Self-Made Mask tip, we looked at how you can use the color channels to make the image select itself. Photoshop’s RGB color channels encode color information in a particular way, such that each channel results in a different black & white image. All you have to do is coax them out. You can also take advantage of Photoshop’s Lab mode to produce yet another black & white version, as we’ll see shortly.

What’s Going on in the Color Channels

All of the colors we see can be produced by mixing different proportions of red, green, and blue light. The Red, Green, and Blue channels work on the principle of mixing those three spectral primaries, and it’s the way color is reproduced in any light-emitting color device, whether it’s a computer screen, a TV, or a projector.

In essence, the color channels work like specialized masks within Photoshop. Each pixel in a color channel corresponds to a pixel within the image, and controls the luminance level (the amount on a scale from to 255) of red, green, or blue light being mixed into that pixel. The luminance levels in each pixel of your image trace back to the intensity of the light that struck the corresponding pixels in your camera’s sensor when you pressed the shutter.

Just as with a mask, black conceals and white reveals in the color channels, so If a particular pixel is pure red, it will be white (255) in the Red channel and black () in the Blue and Green channels. Neutral colors have equal amounts of red, green, and blue, so a neutral 5% gray pixel will have values of 128 in each of the Red, Green, and Blue channels, and so on.

Lab Color

The nature of RGB color is that the R, G, and B values for a specific color will be different for each device or color space, and some devices will be unable to produce certain colors. For that reason, RGB color is described as being device-dependent. Enter Lab color.

The Lab color model maps out all human-perceivable colors in a three dimensional coordinate system that is device independent. It’s the color model that’s at work under the hood of Photohshop, and it’s what allows Photoshop to manage color and convert between color spaces. In the Lab model, colors are expressed in terms of Lightness (L), tint (a), and color temperature (b). You’ll see hints of the Lab color model at work in various Photoshop features. For example, the Temperature and Tint sliders in Camera Raw and the Color and Luminosity blending modes are all based upon the Lab model.

Creating a Black & White Image from the Lightness Channel

While the a and b channels don’t yield very useful black & white images, the Lightness channel produces a high-quality black & white image. To extract a black & white image from the Lightness channel, we’ll convert image to Lab Mode and convert the Lightness channel to grayscale. The process is analogous to converting the R, G, or B channels to grayscale as above.

1. Select Image > Mode > Lab Color from the menu bar.
2. Activate the Channels panel and click on the Lightness channel to select it.
3. Click the eyeballs to turn off the a and b channels, so you can see the black and white version.
4. Select Image > Mode > Grayscale from the menu bar.  If prompted, click Yes to discard the other channels.

Black & White Images with the Channel Mixer

The conversion methods shown so far all convert your image to black & white from a single channel or according to a preset mixture of channel information. You can use the Channel Mixer’s Monochrome option to combine channels to create a richer image. The command works best in RGB-mode images. It is somewhat useful in CMYK mode, and useless in Lab mode.

Before invoking the Channel Mixer command, it’s a good idea to activate your Channels panel and click on each channel to review its strengths and weaknesses. In general, the Red channel has the brightest skin tones and the Green channel has the best luminance info and cleanest details. The Green channel tends to look most like a “conventional” black & white image. The Blue channel tends to be where the “gunk” hangs out. You’re likely to see the most luminance noise there, along with freckles, blemishes, and mottled skin. However, this isn’t always the case, so you want to look at each of the channels to determine which channels to emphasize or deemphasize.

Rather than applying it as a direct (destructive) adjustment to your image (via the Image > Adjustment menu), it’s best to apply the Channel Mixer as an adjustments layer. You can add the adjustment layer via the icon buttons on the Adjustment panel or via the black and white circle icon at the bottom of the Layers panel. If your Adjustments panel is showing controls instead of icons, click the left-facing arrow at the bottom left corner of the panel to return to the icons.

Once the Channel Mixer controls apper in the Adjustments panel, click the Monochrome box to begin the conversion. The Channel Mixer will default to the same mix that it uses to create a grayscale image with the Image > Mode > Grayscale command: 4% R + 4% G+ 2% B. From there, you can adjust the settings by any of these methods:

• Scrub the cursor (drag toward the left or right) in the label area above the slider to change its settings
• Drag the pointer on the slider
• Click in the value box and type a value
• Click in the value box and use the Up or Down arrow keys to change the value in increments of 1. Hold the shift key down and tap the arrow keys to change the value in increments of 1.

You can enter positive or negative values into the boxes. You just want the grand total to add up to 1%, more or less. 1% R - 5% G+ 5% B is perfectly valid. A total that is slightly over (~13%) isn’t terrible, but under by more than 5-1% tends to produce murky results.

The main pitfall of the Channel Mixer is that it can clip highlights. For that reason, it’s best to keep an eye on your Histogram panel as you adjust the settings. The appearance of the histogram is more important than the total percentage. If there is a gap at the top of your highlights, you can let the total go above 1% to brighten the image.

Don’t use the Constant setting in the Channel Mixer panel. If you want to tweak the histogram, you can add a Brightness/Contrast layer. Make sure the Use Legacy option is turned off. Most of the time, the contrast setting alone will get the job done, but it’s OK to increase brightness.

Another approach to enhance the Channel Mixer result is to duplicate the background layer and apply a Shadows/Hightlights adjustment to it. With the Channel Mixer layer turned on and the duplicate layer beneath it, you can see the resulting black & white image as you adjust the Shadows/Highlights controls. Later, we’ll look at the Black & White adjustment later, which can also be used with Shadows/Highlights in this way.

Multiple Mix Scenarios

There’s no one best way to mix channels in a given image, so your best strategy is to try different scenarios and compare them. You can duplicate a Channel Mixer layer, turn off the original, and change the settings of the copy, or turn off the current mixer layer and start a new one from scratch. Whenever you reactivate a Channel Mixer layer, you can double-click its thumbnail in the Layers panel to bring up its controls in the Adjustments panel.

Once you’ve created two or more Channel Mixer layers, it can become tedious to switch between the different versions for comparison. You can use the Layer Comps feature to easily compare versions:

1. Switch on one of your Channel Mixer layers with its eyeball icon.
2. Activate the Layer Comps panel. (Window > Layer Comps)
3. Click the upturned page icon (Add New Layer Comp) at the bottom of the panel
4. Enter a descriptive name and be sure Visibility is checked (the default setting). You don’t have to record position or appearance for most scenarios.
5. Click OK
6. Click the eyeball to turn off the previous Channel Mixer layer and click another to turn it on.
7. Repeat steps 3-5 above for the new layer.
8. Repeat steps 6 and 7 as many times as necessary to record all of your Channel Mixer variations.
9. To view a particular scenario, click the box to the left of its layer comp

In case you were wondering, the Layer Comp’s Position option records the horizontal and vertical location of a pixel layer’s contents and Appearance records the layer styles (e.g. Drop Shadow or Blend If settings).

The Black & White Adjustment

The Black & White layer one of the preeminent color adjustments in all of Photoshop. It’s direct and easy to use. Once you understand how it maps color ranges to tones, its results are predictable. It works in a very different way than Channel Mixer, and that’s why it doesn’t make the Channel Mixer approach obsolete. Which one to use depends on your creative intent: while the Black & White adjustment is great for “straight” conversions, the Channel Mixer allows for much more extreme effects.

The sliders in the Black & White adjustment divide the hues on the color wheel into 6-degree color ranges. Moving the sliders maps the corresponding range of colors in the image to a particular shade of gray, making them lighter or darker as needed. To determine which moves are likely to produce the best results, you can use the eyeball icon to toggle the adjustment off and on. Skin tends to respond to the red and yellow sliders, while skies respond to cyans or blues. As far as Photoshop is concerned, the colors of foliage and grass are more on the yellow side than green, so you’re likely to get the best results adjusting the yellow slider.

Some of the options in the preset menu at the top of the panel can be useful as a starting point. The Blue, Red, and Yellow Filter settings work much like those filters would work on a camera with black and white film. Once you’ve selected a preset, you can further adjust the sliders to refine the result.

If you have large areas of color in your image, you may be successful using the targeted adjustment feature. Click the finger icon in the panel and drag horizontally in the image to use it. The feature samples the color in the image to decide which slider to move, but errors in sampling often mean that you’re not adjusting the color you really want. The Auto button also doesn’t work very well.

A popular technique is to allow some color to show through in a black and white image. You can achieve this easily by blacking out the area of the layer mask of the where you want the color to show through. Use any selection method (e.g. Quick Select) to create a selection around the item you want to reveal in color and do any of the following:

• If the layer does not have a mask, hold down the Alt (Mac: Option) key and click the Add Layer Mask icon at the bottom of the Layers Panel.
• If the layer has a mask, click the layer mask thumbnail to select it and choose Edit > Fill to bring up the Fill dialog, then set the Contents menu to Black and click OK.
• Optional: Use the Feather control in the Masks panel to smooth the edges of the mask.

Best of Both Worlds: Combining Channel Mixer with Black and White

You can mix both methods by stacking Channel Mixer and Black & White layers, then masking the bottom adjustment so that the color shows through to the upper adjustment. The layer on the bottom is the main effect, so if most of the Channel Mixer result is what you want, it goes on the bottom. You use the mask cut through the effect where it’s not working and allow the layer above to adjust it. The top layer does nothing where it sees black and white.

1. Add a Channel Mixer layer to your color image, adjust the settings and turn off its visibility with the eyeball icon.
2. Add a Black & White layer above the Channel Mixer layer, and adjust the settings for a satisfactory result.
3. Click the eyeball icon on the underlying Channel Mixer layer to activate it.
4. If the Channel Mixer (underlying) layer does not have a mask, click the Add Layer Mask icon at the bottom of the Layers panel.
5. Bracket marks should appear around the corners of the layer mask icon to indicate that it’s selected.  You can click the layer mask thumbnail to be sure that it’s activated.
6. Tap B to activate the Brush tool, and adjust size as needed.
7. Your foreground and background colors should be black and white.  You can tap D to switch to the default (white foreground, black background)  and X to swap foreground and background colors.
8. Paint in the image area to apply black to the mask where you want to hide the Color Mixer effect,  allowing the Black & White conversion to show instead.

Colorized Images

Adding hints of color to the neutral tones of a black & white image can add visual impact or even emotional overtones. Applying a warm or cool hue creates a monochrome effect. Another strategy is to apply complementary colors to the highlights and shadows respectively to create a duotone effect that can enhance the feeling of depth and richness. A third technique is to use a gradient map to assign different hues to different luminance levels.

The Tint Option in the Black & White Layer

When you click the Tint checkbox in a black & white layer, it has the effect of combining the luminance values of the black & white image with the Hue and Saturation values of the selected color to colorize each pixel in the image. It does the same as adding a solid color layer with the same hue and sataturation settings and then changing the blending mode to Color. That, by the way, is how you can achieve that effect with Channel Mixer, since it doesn’t have a colorize option.

The default Tint color is a yellowish, over-the-top sepia effect. To change the color, do the following:

1. Click the colored square next to the Tint checkbox; A color picker dialog will appear.
2. Optional: Change the Hue value.
3. Optional: Change the Saturation value

Gradient Map: The Best Way to Infuse Color Into a Black & White Image

The Tint option is limited, because it applies the same hue and saturation value to every pixel in the image, regardless of its luminance level. The Gradient Map command allows you to apply different hue and saturation values to different luminance ranges. To apply the effect with a preset map, do the following:

1. add a Gradient Map layer via the Adjustments panel or by selecting from the menu at the bottom of the Layers panel.

2. In the Adjustments panel, click the blue button with the triangle at the right edge of the gradient to show the loaded gradients.
3. Click a gradient, such as Copper, to apply it.
4. Optional: Change the blend mode to Color. (Leaving the blend mode set to normal allows you to remap luminance via the color stops in the gradient.)

By the way, the gradients that ship with Photoshop aren’t very helpful for application with the Gradient Map feature. In the video course, Deke supplies 14 useful gradients and shows how to load them.

Adjusting the Gradient Map Effect

You can build gradients from scratch or edit existing ones easily. Adjusting the gradients allows you to affect both the color and the luminance of various parts of your image. Click the gradient strip in the Adjustments panel to open the Gradient Editor dialog. As with the Channel Mixer before, it’s a good idea to keep an eye on the Histogram to make sure you don’t clip highlights.

• Click the area beneath the gradient to add a color stop.
• Drag a color stop downward to tear it off and remove it.
• Drag color stops to the right to darken the image or to the left to lighten.
• To increase contrast, drag stops toward the center, i.e. drag the stops on the left side toward the right, and the stops on the right side toward the left.
• Double-click a color stop to bring up the color picker dialog. Use the H, S, and B values to adjust the color of the stop.
• Think of brightness as a percentage (i.e. = black and 1 = white) instead of the usual -255 value levels you’re used to.
• Increasing saturation values darken the color, and reducing saturation lightens the color.

To save your modified gradient, enter a name for the the gradient first, then click the New button. If you click New first, your new gradient will be named Custom.

To delete an unwanted gradient, Alt-click (Mac: Option-click) on it. If you click a gradient to load it before deleting it from the list, you can enter a new name and click New to save it again.

The other way to modulate the effect of the Gradient Map effect is to adjust the blending mode or opacity of the layer.

• The Color blending mode applies only the hue and saturation of the gradient map, preserving the luminance of the underlying grayscale image.
• Overlay and Soft Light modes are especially useful for adding contrast
• Use Opacity with any of the modes to constrain how strongly they are applied.

So there you have it. “Black & white” turns out to mean a world of options, none of which have to be boring or cold and gray. Just convert a channel or use a preset conversion when you need something quick and dirty, or take your time with the Black & White or Channel Mixer command, masking, and Gradient Map to create a breathtaking magnum opus. Happy editing!