In an earlier post I described how one of the final steps of my workflow is to add what I refer to as structure lines to the image. The bottom half of the image below has structure lines but the top half does not. Moving the slider up and down will let you see the overall effect of having or not having these lines as part of the final image.

The featured image for this post shows what the structure lines for this image look like before being applied. To create the lines I made a copy of the original photograph (the version that does not have any of my brushwork or color enhancements), and applied an edge sensing filter to the copy. An edge sensing filter acts like a piece of tracing paper covering the image, where some invisible hand has gone through and traced over the edges that are present in the image. The invisible hand in this case is the edge sensing filter software and the settings I make when applying the filter determine what the software will interpret as an edge. Moving the slider up and down on the image below will show the effect of the filter on this image with the settings I selected.

After creating the structure lines, the next step is to apply them to the image.  I begin by opening the image file that contains all of my brushwork and color enhancements. Then, I make a copy of the image with the structure lines and paste it on top of the brushwork/enhanced image. My Layers tab will now appear as shown on the right. At first, all that I see is the structure lines. I need to do something that will make the white background of this new layer disappear, leaving behind the black structure lines.

To accomplish this I will change the blending mode of the layer with the structure lines. The blending mode controls how each layer interacts with the layers below it. The default mode of every new layer is set to Normal. Using the drop down menu, I change the blending mode to Multiply. Multiply mode causes the white portion of the layer to disappear, leaving behind my structure lines. In the image below, the top part shows what happens when the blending mode is set to Multiply, and the bottom part shows what the image looks like when the mode is still set to Normal. 

Usually I will lower the Opacity setting of the layer with structure lines to somewhere between 20% to 30%. This gives the lines a more subtle impact on the final image. I might also decide to completely hide some of the structure lines by applying a layer mask onto the layer with the structure lines. But layer masks will be the topic of another post.