Sharpening has helped bring out the details in the image and made it look more, well, sharp. Now it pops! Yay!
What's going on here?
You can stop right now if all you want to know is how to add pop and aren't interested in being able to do even a lot better. But, For me the interesting part of this chapter is the theory behind it. Granted the technique is a super simple way of improving tons of shots, but understanding why it works opens the door to a greater understanding of how to use (and not misuse) LAB color corrections and of digital color correction in general. Human sight is a marvelously complex and highly evolved system. It self calibrates to emphasize differences in color and in shade. When we are in the middle of the forest surrounded by infinite subtle shades of green, our vision pulls these shades apart allowing us to see enormous variation. On the beach in the late afternoon, we can discern traces of the impending sunset and see the complexity of hue in the sand and sky. But the camera doesn't do this. It doesn't "know" when to do it. When we look at a picture, our vision does not self calibrate because the picture only occupies a small portion of our field of view and is surrounded by all kinds of competing cues. So the picture won't capture the same intensity and variety of color we saw when we took it. Even if it is a faithful rendering of the "true" colors of the scene, it does not capture what we saw.
The basic LAB enhancement can restore the picture so that it captures the vision of our memory. Steepening the A and B curves moves colors apart from each other. This kind of symmetrical curve steepening applies a constant multiplier to the colors. If it was X amount of green before, it will be X*N green after and similarly for magenta, blue, and yellow. The green gets greener in proportion to how green it was to begin with. The difference between blue and yellow is magnified as slight variations from neutral are pushed away from neutral toward in the direction of their tint. So the sky of my shot becomes more of a tapestry of different shades of blue. The grass and hills in the background all show greater color variation. Similarly for the other elements of this picture. It's mush more as I remember it.
Steepening the L curve over the areas of interest in the image similarly apes the way our vision works. The steeper the curve, the greater the detail, as Dan likes to say. I found no interesting detail darker than the shadows in the barn. So I pulled the right end of the L curve in almost to that point. I found no interesting detail lighter than that cloud, so I pulled the left end of the L curve in almost to that point. Then I made it a little steeper though the elements of the picture I really wanted the viewer to see.
This tutorial is pure Dan Margulis. The technique described here is taken from Chapter 1 of his book Photoshop LAB Color : The Canyon Conundrum and Other Adventures in the Most Powerful Color Space. Dan is the living grandmaster of digital color correction and enhancement. He has approached the topic as both a scientist and artist, has constantly innovated, and has written on the topic with enormous and increasing lucidity. Anyone who want to get good at photoshop to make both color and black and white images look better and more realistic can peruse no better path than to read his books and try to master some of his ideas and techniques. Unfortunately this can't be seen as a short or even a finite process. Dan challenges his readers to really understand color both in theory as well as in practice. The reward is true understanding, independent of any recipe which can be applied though a variety of tools as appropriate. Plus I find Dan's writing a gas to read. He writes well and has a wonderful dry sense of humor which makes the inevitable second reading a pleasure.
This tutorial started it's life as a summary of chapter 1 of Dan's LAB book. It was originally written as a part of a reading book organized as a forum for discussion and understanding of that book. That forum is very much still alive and much more information is available there.
Ask questions about this tutorial in this thread on Digital Grin!