Adobe Photoshop CS4 - Manual (Page 120)

113 USING PHOTOSHOP CS4
Color fundamentals
Last updated 1/10/2010
Images are flattened when converted to Multichannel, Bitmap, or Indexed Color mode, because these modes do not
support layers.
Add a conditional mode change to an action
You can specify conditions for a mode change so that the conversion can occur during an action, which is a series of
commands applied sequentially to a single file or a batch of files. When a mode change is part of an action, an error
can occur if the file being opened is not in the source mode specified in the action. For example, suppose one step in
an action is to convert an image with a source mode of RGB to a target mode of CMYK. Applying this action to an
image in Grayscale mode, or any other source mode besides RGB, results in an error.
When you record an action, you can use the Conditional Mode Change command to specify one or more modes for
the source mode and a mode for the target mode.
1 Start recording an action.
2 Choose File > Automate > Conditional Mode Change.
3 In the Conditional Mode Change dialog box, select one or more modes for the source mode. Use the All or None
buttons to select all possible modes or no mode.
4 Choose a target mode from the Mode pop-up menu.
5 Click OK. The conditional mode change appears as a new step in the Actions panel.
More Help topics
“ Automating with actions ” on page 620
Convert a color photo to Grayscale mode
1 Open the photo you want to convert to black-and-white.
2 Choose Image > Mode > Grayscale.
3 Click Discard. Photoshop converts the colors in the image to black, white, and shades of gray.
Note: The technique above minimizes file size but discards color information and can convert adjacent colors to the exact
same shade of gray. Using a Black & White adjustment layer increases file size but retains color information, letting you
map colors to shades of gray. (See “
Convert a color image to black and white ” on page 175.)
Convert an image to Bitmap mode
Converting an image to Bitmap mode reduces the image to two colors, greatly simplifying the color information in the
image and reducing its file size.
When converting a color image to Bitmap mode, first convert it to Grayscale mode. This removes the hue and
saturation information from the pixels and leaves just the brightness values. However, because only a few editing
options are available for Bitmap mode images, it’s usually best to edit the image in Grayscale mode and then convert
it to Bitmap mode.
Note: Images in Bitmap mode are 1 bit per channel. You must convert a 16- or 32-bits-per-channel image to 8-bit
Grayscale mode before converting it to Bitmap mode.
1 Do one of the following:
• If the image is in color, choose Image > Mode > Grayscale. Then choose Image > Mode > Bitmap.
• If the image is grayscale, choose Image > Mode > Bitmap.