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      In this case, I painted only the window panes, leaving the wood crosspieces 
      unmasked. Actually, I also used the Invert button (third from left of the 
      top row of Mask controls) and a smaller Threshold setting to clean up the 
      crosspieces in the window. Note that when using the Paint tool the mask 
      color appears immediately . . . you don’t need to click an “Apply” 
      button (in fact, there is no Apply button, but a larger window appears with 
      Radius, Transparency, Softness, Tracking and Threshold controls). And to 
      really get a precise mask, you can switch between the Paint tool and any 
      of the geometric drawing tools as much as you like, even changing the Add 
      button to a Subtract button if you need to trim away mask areas. When the 
      mask is the way you want it you need to click OK to create the mask image 
      window (or, as mentioned above, you can directly use the mask just created 
      . . . but it’s wise to save your masks until you are sure you don’t 
      need them again).  
      
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