Pattern Dither
● Diffusion Dither
Figure 2-7 shows the effect each method creates.
6. Click OK to convert your image to Bitmap mode.
FIGURE 2-6: Type a resolution for your output and choose the conversion method from the Use drop-down list.
FIGURE 2-7: An original RGB image converted to bitmap by using 50 % Threshold, Pattern Dither, and Diffusion Dither.
Converting to Grayscale mode
Grayscale images have black-and-white pixels and any one of an additional 254 levels of gray. By converting an RGB image to grayscale, you can make a color image look like a black-and-white photo.
The following two sections explain better ways to create a grayscale image.
Desaturating a layer
You don’t have to give up your color data when you convert to grayscale. As an alternative to using the menu command for converting images to grayscale, follow these steps:
1. Open an RGB image in Elements in Expert mode.
2. Duplicate a layer.
The default Panel Bin contains the Layers panel. In this panel, click the icon in the upper-right corner. From the pop-up menu, choose Duplicate Layer. (A layer is like a clear sheet of acetate that you can draw on, only its digital. For information on working with layers, see Chapter 8.) In this example, we duplicated the layer, adjusted the duplicate layer, and duplicated again to create a third layer.
3. Choose Enhance ⇒ Adjust Color ⇒ Adjust Hue/Saturation to open the Hue/Saturation dialog box, as shown in Figure 2-8.
Alternatively, you can press Ctrl+U (⌘ +U on the Mac).
4. Drag the Saturation slider to the far left to desaturate the image on the selected layer and then click OK.
All color disappears, but the brightness values of all the pixels remain unaffected. (For more information on using the Hue/Saturation dialog box and the other Adjust Color commands, see Chapter 10.)
5. Turn off the color layer by clicking the eye icon in the Layers panel.
In the Layers panel, you see three layers, as shown in Figure 2-9. The top layer in RGB color is hidden from view (notice the diagonal line through the eye icon). The second layer is grayscale. You don’t need to turn off the color layer to print the file in grayscale, but turning it off can help you remember which layer you used the last time you printed or exported the file.
FIGURE 2-8: Open the Hue/Saturation dialog box and move the Saturation slider to the far left to eliminate color.
FIGURE 2-9: The Layers panel shows the grayscale and color layers. You can turn layers on or off by clicking the eye icon.
Following the preceding steps provides you with a file that contains both RGB and grayscale information. If you want to print the color layer, you can turn off the grayscale layer. If you need to exchange files with graphic designers, you can send the layered file, and then the design professional can use both the color image and the grayscale image.
The other advantage of converting RGB color to grayscale by using the Hue/Saturation dialog box is that you don’t disturb any changes in the brightness values of the pixels. Moving the Saturation slider to desaturate the image affects only the color. The luminance (lightness or darkness of any given color) and hue (color) values remain the same.
Choosing the Convert to Black and White command
A menu command exists for converting color images to black and white. Choose Enhance ⇒ Convert to Black and White in either Expert or Quick mode to get to the Convert to Black and White dialog box, as shown in Figure 2-10.
FIGURE 2-10: The Convert to Black and White dialog box.
This dialog box contains these controls for adjusting brightness and contrast in images that you convert to grayscale:
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