Why Are Some Filters and Effects Grayed Out?

If you attempt to access a filter or an effect and it's unavailable (grayed out), there could be several reasons. The bottom half of the Filter menu (from Artistic down) only works on rasterized objects or placed raster images. Moreover, many of the filters only work in RGB mode. Similarly, many Effect menu commands will only work if the document is in RGB mode. As you may know from a previous tip, you cannot switch from CMYK mode to RGB, apply an Effect menu command, and then switch back to CMYK because the effect will be lost.