Keep Your Ink Density Down For Optimal Results
For best results, you should keep your maximum ink density to 300 or less. You can check your ink density in photoshop by opening the “Info” window, open the “Panel Options” (three horizontal lines in the upper right hand corner of the window) and make your “Second Color Readout” Mode: Total Ink. Use the eyedropper tool to go to the darkest areas and check that the total ink does not exceed 300.
If your artwork is 100 cyan, 100 magenta, 20 yellow and 100 black, your ink density is 320. You will usually see high ink densities in heavy black areas. Use your “Selective Color” adjustment and choose “Black”. Reduce the amount of cyan, magenta and yellow while increasing the amount of black. This should give you a dark enough color while reducing the amount of ink in any one area.