This method makes separating dark or dirty colours easier, using a combination of the Spot and Hue filters in the Spot Window.

The Hue filter cannot easily handle dark or dirty colours because they have a certain amount of black in them. Since black is not a hue, the Hue filter has trouble creating an accurate representation of the tones for the selected colour. Therefore, a mid-tone may look stronger than the selected colour in the separation.

The Hue Separation Method gives a more specific separation than the Spot method and quickly removes unwanted colours. However, the Spot separation produces more accurate tone levels than the Hue method. The following method takes the best from both the Spot and Hue separations, to quickly and easily produce smooth tonal layers.

1. Go to Separate Menu > Spot.
2. Change the mode (in the top left hand corner) to Hue. Then tick the box next to the option Tonal.
3. Use the Pipette Tool to select a dark or dirty colour from the design using the Pipette Tool, and then click ‘New’ and ‘Preview’.
4. Adjust the Hue, Boost and Offset slider bars until you are happy with the range of colours left in the separation.
   • Hue - this slider is used to change the delta hue, so it removes the unwanted colours but keeps the tones you want included. The further this slider is pushed to the right, the more specific the colour range is to the selected colour.
   • Boost - this slider is used to boost the chosen tones. This is similar to pushing the gamma curve upwards. For best results, use the boost slider first to enhance the tone range and then apply any gamma needed. This avoids unwanted step tones.
   • Offset - this slider is used to alter the type of colour being picked up in the separation. If you are trying to separate a red colour in a design, some pink and orange may get picked up with it. If you only want the pink hues to be included, it is possible to separate the pinky-reds, without the orangey-reds, by offsetting the colour towards pink.
     
5. Create a Spot filter in the same colour as the Hue filter by changing the mode to Spot and dragging the colour chip from under the Gamma Window into filter list.
6. Change the filter order by dragging the Spot filter above the Hue filter in the window. The snapshot below shows the Hue filter is now sat below the Spot filter.
   
7. Click on the Hue filter and invert its gamma by ^ (control key) clicking on the Gamma Window and selecting Invert from the contextual menu.
   
8. Make the Hue filter a minus (change the ‘+’ symbol to a ‘-’ symbol). This will take this filter away from the Spot filter.
   
9. Use the Boost slider bar to strengthen the tones on the Hue filter and adjust the Gamma if you need to.
   
10. Fix the Preview layer when you are happy with the results by clicking the Fix button on the left hand side of the Spot Window.
11. The new separated 8 bit layer will be added to your Layers Palette and can now be recoloured if necessary. You can also use the Gamma Window (Edit Menu) to make further adjustments to the tonal movement on the layer if necessary.

Learn more about Spot Separations here.