Use the Curves Tool/Palette In Cleaning an Image in Photoshop

How to Use the Curves Tool/Palette In Cleaning an Image in Photoshop?
Use the Curves Tool and the Info Palette to Clean Up an Image
Let’s experiment with checking and changing the colors in this image
using the Curves tool and the Info palette.

1. Open the image.psd file that you created. Position the Info palette near the image. Click on the Eyedropper tool in the toolbox. Verify that all channels are selected in the Channels
palette.

Figure 1.1

3. Use the Eyedropper to check the white in the thickest part of the border and see if it’s really white; all of the numbers in the Info palette should read 0 percent for the CMYK percentages. See Figure 1.1.

4. Using the Eyedropper, hover over the center of the fish’s eye where it is black. Notice the percentages in the Info palette. Mixing the four colors of ink will create this shade of black. (If you wanted to, you could create a black spot color channel.)

5. Using the Eyedropper and watching the numbers in the Info palette, move the Eyedropper over an area of yellow in the image. Choose an area in the fish’s bottom fin around the black dots in that area. Look at the numbers in the Info palette and notice some of the yellow parts of the fin have cyan in them. Because Photoshop has been known to really exaggerate cyans when creating a separation, and if you find this to be true now, you should lower those numbers a bit. In a pure yellow, you should theoretically remove all the cyan.

6. To change the cyan, choose Image>Adjustments>Curves. Choose Cyan in the Channel drop-down list. The changes you make now will only affect the Cyan channel. Because the other channels are visible in the Channels palette though, you can see the effect of your actions
on the entire image.

7. In the Curves dialog box in the bottom left of the grid, pull down the line a little, as shown in Figure 23-6. This will reduce the cyan in the image.

8. Use the Info palette to see if you’ve removed the cyan and gotten the percentages down to 0 percent for (most of) the yellow part of the image. Use the Info palette to look at the before and after numbers for the cyan in the yellow. See Figure 1.2

Figire 1.2

9. When you’ve reduced the cyan and verified that the image still looks as it should, click OK in the Curves palette. 

You can perform the same operations on the magenta, yellow, and black channels if you feel it’s necessary. You’ll have to experiment, print, and experiment some more before you really understand the limits of your

inks, screens, equipment, and, yes, even Photoshop.

Posted in: Photoshop