Here is the starting image. Notice that the body of the car is in direct sunlight, while portions of the engine are in shadow. Parts of the body in direct light (the sticker in the upper right for example) are over exposed and washed out, while some of the engine details are hidden in shadow.

dodgeburn

This is how the image looks in Photoshop. Notice that the only layer in this file is the Background layer.

start

We'll start off by adding a new layer. We want Photoshop to present us with the New Layer dialog when we create this layer so hold down the Alt (mac: Option) key while you click on the New Layer button in the Layers palette.

layerbutton

In the New Layer dialog provide a name for the layer, change the Mode to "Overlay" and check "Fill with Overlay-neutral color (50% gray)".

layerdialog

Now in the Layers palette we have a new "Dodge & Burn" layer that has its blending mode set to Overlay and is filled with medium gray.

Because the entire layer is filled with 50% gray it has no effect on the image. However, any areas of this layer that are lighter than 50% gray will lighten the underlying images and areas darker than 50% gray will darken the underlying images. Let's put this to use and lighten up some of the engine details that are in shadow.

dodgeburnlayer

In the Tool palette, select the brush tool. At the same time press the D key to set the foreground and background colors to black and white, respectively.

brushdefaultcolor

Now that the foreground and background colors are black and white we can quickly swap foreground and background by pressing the X key. Here I have pressed X once to set the foreground color to white.

swappedcolors

In the option bar for the brush tool I have selected a medium sized, fairly soft edged brush. I have also set a opacity of 100% and a flow of 10%. Setting opacity and flow this way means that I can slowly build up the lightening effect in areas that need it.

brushoptions

Here is the area of engine that is in shadow.

predodge

Here I have started lightening by painting with the brush, using a foreground color of white, on my Dodge & Burn layer. Notice how the hoses and clamps are starting to show more detail.

dodge

Here is the Dodge & Burn layer by itself. Notice that it is non-uniform. There was no need for me to be surgically precise with my painting. The combination of the soft edged brush and the low flow value means that I can be pretty rough will still achieving good results.

dodgelayer

Now lets work on a little darkening (burning in darkroom speak). Notice how this decal is little washed out and some of the details are pretty faint?

preburn

Once again, I use the brush to paint onto the Dodge & Burn layer. I'm using the same settings as before, but now I've switched the foreground color to black.

Now the border and text of the decal stand out!

burnt

And here is the portion of the Dodge & Burn layer above the decal.

Again, notice that I wasn't terribly precise with my painting.

burnlayer

And here is the image with the Dodging and Burning applied.

done

One more note: If you do something you don't like to your dodge & burn layer you can always undo what you've done by painting the area in question back to 50% gray. To get 50% gray as the foreground color, just click the foreground color swatch in the tool palette to open the Color Picker. In the color picker simply set the saturation "S" value to 0%, and the brightness "B" value to 50%.

colorpicker