Color Correcting Images in the RGB Color Space

Color Correcting Images in the RGB Color Space

What is the best tool to use when color correcting images in Photoshop? There are many tools that can be used to make color adjustments to images, and most are capable of giving good results. However, the real issue is not the tool being used to correct color, but utilizing the most appropriate color space for correcting color images.

Many designers and prepress professionals will convert images to CMYK first, and then try to color correct images. This is not the best choice as you will always get better results when you color correct images in the RGB color space before converting them to CMYK. There are two major reasons for this:

  1. When images are converted from RGB to CMYK, you lose color information—a lot of it. As a result, you (and Photoshop) have fewer colors to work with, or average, when attempting to make color changes to an image. The RGB color space contains millions of colors (theoretically), while the CMYK color space only contains thousands.
  2. When images are converted from RGB to CMYK, you’re creating the black separation. When the black separation is created, the cyan, magenta, and yellow is reduced within the image, and replaced with black ink. Depending upon how much cyan, magenta, and yellow was eliminated in the separation, it can be very difficult—or even impossible—to make color adjustments to an image.

So, given all of the disadvantages, why do people choose to correct color in CMYK? First, because when images are converted to CMYK, you can see what colors are being lost, and then color correct and adjust those colors being affected. Second, many convert to CMYK because it just makes sense from a color correction standpoint. If you need to reduce the cyan in an image, you might use the Curves tool, select the cyan channel, and bend the curve down. Or if you needed to add yellow, bend the yellow curve up, and so on.

But what if you’re working in the RGB color space and want to reduce the amount of magenta in an image? Which channel do you use? All you have to remember is RGB and CMY, in that order. Cyan can be adjusted in the red channel, magenta in the green channel, and yellow in the blue channel.


Finally, if you want to see an on-screen preview of what the image is going to look like when it’s converted to CMYK while you’re working in the RGB color space, simply select View>Proof Colors. This gives you the best of both worlds: The image remains in the RGB color space giving you the full gamut of colors for correction while a preview of what the image will look like when it’s converted to CMYK is shown in Photoshop.


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