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Adobe Photoshop Help
Working with Color
Using Help
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To convert between 8 bits per channel and 16 bits per channel:
1
To convert to a 16-bit-per-channel image, first flatten the image. (See
“Flattening all
layers” on page 295
.)
2
Choose Image > Mode > 16 Bits/Channel or 8 Bits/Channel.
Converting between color modes (Photoshop)
When you choose a different color mode for an image, you permanently change the color
values in the image. For example, when you convert an RGB image to CMYK mode, RGB
color values outside the CMYK gamut (defined by the CMYK working space setting in the
Color Settings dialog box) are adjusted to fall within gamut. Consequently, before
converting images, it’s best to do the following:
•
Do as much editing as possible in the image’s original mode (usually RGB from most
scanners, or CMYK from traditional drum scanners or if imported from a Scitex system).
•
Save a backup copy before converting. Be sure to save a copy of your image that
includes all layers in order to edit the original version of the image after the conversion.
•
Flatten the file before converting it. The interaction of colors between layer blending
modes will change when the mode changes.
To convert an image to another mode:
Choose Image > Mode and the mode you want from the submenu. Modes not available
for the active image appear dimmed in the menu.
Images are flattened when converted to Multichannel, Bitmap, or Indexed Color mode,
because these modes do not support layers.
Converting between Grayscale and Bitmap modes
(Photoshop)
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. To convert an image to Bitmap
mode, you must first convert it to Grayscale mode. This removes the hue and saturation
information from the pixels and leaves just the brightness values. However, because few
editing options are available for Bitmap-mode images, it’s usually best to edit the image in
Grayscale mode and then convert it.
Keep in mind that a Bitmap-mode image edited in Grayscale mode may not look the same
when converted back to Bitmap mode. For example, consider a pixel that is black in
Bitmap mode and then edited to a shade of gray in Grayscale mode. If the gray value of
the pixel is light enough, it will become white when converted back to Bitmap mode.
