Photoshop's Luminosity Mask

ImageMy technique drops out the background white of drawings that are scanned and allows illustrators to work on the sketch in Normal mode. The advantage to this process is to do away with converting the scanned sketch into Multiply mode in order to color it. In Multiply mode the sketch loses integrity when paint fills "multiply" through the sketch from below and becomes mingled as a tint of the sketch color above. Furthermore, you have to convert the sketch back to normal mode to color it and all the white comes back obscuring the effect the color change has with the colors layered underneath.

 

Technique


My technique drops out the background white of drawings that are scanned and allows illustrators to work on the sketch in Normal mode. The advantage to this process is to do away with converting the scanned sketch into Multiply mode in order to color it. In Multiply mode the sketch loses integrity when paint fills "multiply" through the sketch from below and becomes mingled as a tint of the sketch color above. Furthermore, you have to convert the sketch back to normal mode to color it and all the white comes back obscuring the effect the color change has with the colors layered underneath.

First scan your sketch and perform all the rituals of cleaning it so that the cleanest possible sketch is attained with desired contrast. Personally, I sketch in dark, bold thick and thin outlines with a Faber-Castell® 4B graphite pencil. These scan almost as black as ink lines and therefore I no-longer use pen & ink as an illustration medium. Image

 

Here is the trick: go to the bottom of your channels palette and click on that dotted circle icon on the left. This creates a luminosity mask. What that means is that all the white has been selected in your scan. Invert this selection. Now you have selected every shade of grey in your sketch. Only the sketch is captured this way and this isolates it in its entirety from the white of the background. Now, create another layer and your selection will apply to it instead of the source layer. Fill the selection with black and discard the background layer. Your sketch should remain in a transparent layer. It may look too light, but create another layer under it and fill it with white and you get the same image with which you started. Image

 

Recording the steps as an action


If this seems complicated, you can abbreviate the series of routines I just described by recording them as an action in Photoshop. I perform the whole process by simply hitting my F1 key, which I have assigned as a keyboard shortcut for the action. If you're unsure, follow these steps:

  1. Open an image to which you want to apply this technique;
  2. Pull down Window from the Menu and select Action, or hit Option>F9 (Mac);
  3. Click on the "Create new action" icon next to the trash icon at the bottom of the palette;
  4. Name the action;
  5. Assign a Function Key to start the action;
  6. Click the Record button;
  7. Now, go through each step I outlined above to achieve the effect of dropping out the white background;
  8. When done with the routines, click on the square button at the bottom of the Actions palette and the action is created. From now on when you need that scanned file converted, just hit the key command(s) you assigned for this technique.

 

From this point you can convert the file to color and as long as you lock the sketch layer you can color the sketch and nothing else any way you choose. The color stays completely loyal because it is an opaque color to the extent that its shade obscures layers underneath. Color fills can now show through from behind where the white once was in exactly the same way cell vinyl acrylics were once layered on acetate in Disney cell animations. I put modeling, highlights, and added scanned instruments on a layer on top of the sketch layer. Any effect can be applied to these layers and that should give illustrators a more intuitive way of visualizing and working with their Photoshop files. Image

 

Biography

Carl Clingman is a Wisconsin native. He received his B.S. from the University of Wisconsin-Madison and earned an Associate degree in Commercial Art. Carl has a Master of Arts from the Johns Hopkins University School of Medicine.

After graduate school, Carl worked for two years in Chicago at the Anatomical Chart Company as an Associate Art Director before moving to Texas to work for ten years as a staff medical illustrator at Baylor College of Medicine. After Baylor, Carl worked as a Medical Illustrator/Senior Graphic Designer at University of Texas-Houston Medical School.

Carl moved back to the north central Midwest to accept his lifelong dream job as a medical Illustrator for the Mayo Clinic in Rochester, Minnesota.