Now, about today's image. Basically it's a shot of a knot in a piece of sawn barn board. It's a plain old flat chunk of wood. The depth from the high spot to the lowest spot is probably no more than a sixteenth of an inch, but notice how it appears to come forward in the image and drop off on a completely different plane. All images taken in a RAW space are pretty much flat. A little interest can be added using Adobe Photoshop Lightroom's (LR) Highlights, Shadows and Contrast sliders, but it is kind of limited. Back in the days of film and darkrooms people made print after print Dodging and Burning small areas to either bring the area forward of push it back in the print. We "should be" doing the same thing today, but we don't have to blow several sheets of expensive photographic paper to see our progress. To find out how to using LR's Adjustment Brush to Dodge and Burn, hit the "Read More"
The Adjustment Brush can be used as a hammer or as a feather. The former is great for changing the look of a sky, or darkening (or lightening) a large portion of an image. The latter for sculpting pieces of an image. If you flip back a few post you'll see images with very well defined shadows and highlights. I use the technique we're discussing today on things like clothing to emphasize the folds of the fabric a lot. In today's image the "folds of the clothes" relate to the texture of the wood.
The big deal with getting depth and dimension is putting light next to a shadow. The lighter area appears to come forward and the shadow area seems to recede. In today's image the natural contours of the wood were followed. The darks were made darker and the lights made lighter.
In past posts I've talked about how to do this same thing using two Curves Adjustment Layers in Adobe Photoshop (PS). There you take a fine (I use about ten pixels), relatively hard (about 95%) Brush and draw in lines everywhere I need (or want) a shadow. First exaggerate the curves (bring up the right quarter of the lights and down the left quarter of the darks. Then you make the Adjustment Layer Mask Black and paint the lines with white. You won't get white, but will see a shade of the tone you lay down the line on. Darker areas will show up dark and lighter areas not as dark. Once you define all your lines you'd blur the Mask until the physical line disappears and become shades. (Usually between a ten and twenty pixel blur)
But, unless you're doing (or have done) something more that required going to PS, why bother. The same effect can be achieved in LR. Make the Adjustment Brush a reasonable size for the areas you'll be working on. It doesn't have to be close or anything because LR will pickup on the color you put the cursor on and not bother the surrounding colors. I've used a Brush about ten times the size of the line I wanted to darken (or lighten) and LR has tracked only the line. Let the Brush have a reasonable feather (but this, again, can be changed afterwards) and "paint" away. You need to drop one Pin for the Highlights and one for the Shadows. In the dropdown for the Adjustment Brush, set one to Burn (darken) and one to Dodge. Adjust as needed.
So, add depth and dimension to your images to make the viewer's eye follow the path you want them to take through your image. Make them "read" your image they way you intended.