Photoshop FAQs


How to convert an image to another color mode:

You can change an image from its original mode (source mode) to a different mode (target mode). 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. As a result, some image data may be lost and can’t be recovered if you convert the image from CMYK back to RGB.

Before converting images, it’s best to do the following:

Do as much editing as possible in the original image mode (usually RGB for images from most scanners or digital cameras, or CMYK for images from traditional drum scanners or imported from a Scitex system).

Save a backup copy before converting. Be sure to save a copy of your image that includes all layers so that you can edit the original version of the image after the conversion.

Flatten the file before converting it. The interaction of colors between layer blending modes changes when the mode changes.

Note: In most cases, you’ll want to flatten a file before converting it. However, it isn't required and, in some cases, it isn’t desirable (for example, when the file has vector text layers).

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.

Correcting Colors in CMYK and RGB

Although you can perform all color and tonal corrections in RGB mode and most adjustments in CMYK mode, choose a mode carefully. Avoid multiple conversions between modes, because color values are rounded and lost with each conversion. Don’t convert RGB images to CMYK mode if they are meant for on-screen display. For CMYK images that are separated and printed, do not make color corrections in RGB mode.
If you must convert your image from one mode to another, perform most of your tonal and color corrections in RGB mode. You can then use CMYK mode for fine-tuning. The advantages of working in RGB mode are:

RGB has fewer channels. As a result, your computer uses less memory.

RGB has a wider range of colors than CMYK, and more colors are likely to be preserved after adjustments.

You can soft proof colors to see an on-screen preview of how your document’s colors will look when reproduced on a particular output device. See About soft-proofing colors.

You can edit an image in RGB mode in one window and view the same image in CMYK colors in another window. Choose Window > Arrange > New Window For (Filename) to open a second window. Select the Working CMYK option for Proof Setup, then choose the Proof Color command to turn on the CMYK preview in one of the windows.


How to convert a color photo to Grayscale mode

Open the photo you want to convert to black-and-white.

Choose Image > Mode > Grayscale.

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.