Accessing Grayed-Out Filters In CMYK
One of the bad things about converting from RGB mode to CMYK mode (under the Image menu) is that many of Photoshop’s coolest filters can only be applied in RGB mode, and once you’re in CMYK mode, many of them are grayed out in the Filter menu, so they can’t be accessed. So what do you do if you really want to use one of those filters? (Whatever you do, don’t convert back to RGB mode, then back to CMYK. That’s image suicide.) Instead, try this tip: In the Channels palette, click on the Cyan channel. Go to the Filters menu and you’ll notice that all those grayed-out filters are now suddenly available. All you have to do now is apply the filter you want to each channel individually (once each on Cyan, Magenta, Yellow, and finally the Black channel), and the filter will appear as though you applied it to the entire image (in reality, you did—you just did it the more laborious way). One way to speed up this process is to create an action that will do it all for you with one click of the mouse.