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Artwork that will be commercially reproduced and that contains more than a single color must be printed on separate master plates, one for each color. This process is called color separation and most commonly uses cyan, yellow, magenta, and black (CMYK) inks. In Photoshop, you can adjust how the various plates are generated.

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To create the illusion of continuous tones when printed, images are broken down into a series of dots. When printing photos on a printing press, this process is called halftoning. Varying the sizes of the dots in a halftone screen creates the optical illusion of variations of gray or continuous color in the image.

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Note: Although inkjet printers also use dots to create the illusion of continuous tones, they use a different type of screen process that does not vary the size of the dots. Instead, inkjet printers use dots that have a uniform size and that are much tinier than the dots used by most printing presses.

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The simplest types of images, such as line art, use only one color in one level of gray. A more complex image, such as a photograph, has color tones that vary within the image. This type of image is known as a continuous-tone image.

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For most users, printing a file means that the Adobe Photoshop application sends the image to an inkjet printer to print a photograph. Photoshop can send your image to a variety of printing devices to be printed directly onto paper or to be converted to a positive or negative image on film. In the latter case, the film can be used to create a master plate for printing by a mechanical press.

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Whether you are printing an image on your desktop printer or sending it to a prepress facility, knowing a few basics about printing will make the print job go more smoothly and help ensure that the finished image appears as intended.

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# (Photoshop) Use the histogram to check the quality and tonal range of the image. For information on using the histogram, see Using a histogram to view the tonal range of an image (Photoshop).
# Adjust the color balance to remove unwanted color casts or to correct oversaturated or undersaturated colors.

You can choose from the following color adjustment methods:

(Photoshop) Auto Color command

Quickly corrects the color balance in an image. Although its name implies an automatic adjustment, you can fine tune how the Auto Color command behaves. For more information, see Using the Auto Color command (Photoshop).

(Photoshop) Match Color command

Matches the color from one photo to another photo, from one layer to another layer, and from a selection in an image to another selection in the same image or different image. This command also adjusts the luminance and color range and neutralizes color casts in an image. For more information, see Using the Match Color command (Photoshop).

(Photoshop) Color Balance command

Changes the overall mixture of colors in an image. For more information, see Using the Color Balance command (Photoshop).

Hue/Saturation command

Adjusts the hue, saturation, and lightness values of the entire image or of individual color components. For more information on the Hue/Saturation command, see Using the Hue/Saturation command.

(Photoshop) Replace Color command

Replaces specified colors in an image with new color values. For more information on the Replace Color command, see Using the Replace Color command (Photoshop).

(Photoshop) Selective Color command

Adjusts the amount of process colors in individual color components. For more information on the Selective Color command, see Using the Selective Color command (Photoshop).

(Photoshop) Channel Mixer command

Modifies a color channel and makes color adjustments not easily done with other color adjustment tools. For more information on the Channel Mixer command, see Mixing color channels (Photoshop).

Levels command

Adjusts color balance by setting the pixel distribution for individual color channels. For more information on the Levels command, see Using Levels to adjust color (Photoshop).

(Photoshop) Curves command

Provides up to 14 controls points for highlight, midtone, and shadow adjustments for individual channels. For more information on the Curves command, see Using the Curves dialog box (Photoshop).

Photo Filter command

Makes color adjustments by simulating the effects of photographing with a Kodak Wratten filter in front of a camera lens. For more information on the Photo Filter command, see Using the Photo Filter command (Photoshop).