This tip, using Smart Objects, is just awesome; and I owe thanks to Theresa Jackson of The Photo Arts Group for sharing it with me.  As soon as she explained it, I understood immediately the power and implications of this technique, and kicked myself for not having thought of it before.  I'm sure others have been doing this for years, but I've never personally seen it published anywhere.  Besides being useful as a dodge and burn technique, and for creating natural looking high dynamic range images, it can be used for countless other effects while maintaining very high quality, and avoiding much of the noise and artifacts often seen when stretching the boundaries of other editing tools.  Another great example is mixing color balance which I'll give an example of later. For this to work properly, you must record your image in RAW and open it in ACR (Adobe Camera Raw). At this point we could do some editing, but the beauty of using Smart Objects is we can return to ACR as often as we like. At the bottom of the ACR screen, there is some text in blue. In my example it reads: Adobe RGB (1998)/ 16 bit; 3872 by 2592 (10.0MP); 240 ppi, (and is no longer in blue).  Click on this text and the Workflow Options dialog opens (shown at left).  Be sure to check the box: Open in Photoshop as Smart Objects.  Then click Open Object.  

The image is brought into Photoshop as a Smart Object which can be edited multiple times.  Here is what makes it so powerful.  From the menu, select Layers, Smart Objects, and then New Smart Object via Copy.  Now you have two identical smart object layers in your Layers Pallet. As you can see in the image at the left, this image was taken of a beach from within a grass hut.  The result is an overly bright beach and sky and an underexposed interior.  A very common problem in home interior photography. We will be making adjustments to both layers and using layer masks to hide and reveal what we wish.  In my example, I'm going to under expose the bottom layer to bring back the highlight details and over expose the top layer to reveal the shadow details. By double clicking the bottom layer, we reopen ACR.  From there we can use the Exposure, Recovery and Brightness sliders to adjust where we like the highlights.  When satisfied, click Done to return to Photoshop.  Now, double click the top layer to open it in ACR.  Using Exposure, Fill Light, and Brightness sliders (there are other ACR tools that can be used here as well) to reveal the shadow detail.  Click Done to return to Photoshop when satisfied. Next, add a layer mask and fill it with black to hide everything.  Using a soft brush with the foreground color set to white, paint over all of the dark areas to reveal the detail we just made to that smart object layer.  How careful you need to be in your masking depends on the image and other factors.  Make your brush smaller as you paint in detailed areas where critical areas meet, but you should already know how to do this if you been using Photoshop for very long. Here is the final result.  Essentially a high dynamic range image from a single exposure without some of the un-natural HDR look, all under your personal control and vision.  This technique isn't always the best one for every situation, but it is a powerful tool at your disposal when needed.   Here is another great use for this technique.  I recently got back from a trip to Lower Antelope Canyon. This was my third trip to Antelope Canyon and I was hoping to get some shots that included deep purples and blues that I've seen in some pictures from this canyon.  Although the sandstone canyon is very red in color, the purples and blues can only be captured  in the deep shadows, while still being able to record the reds and oranges and even yellows where the brighter light is found.  To do this it is best to be there in early morning or late afternoon.  The popular light shaft images are best captured near noon when the sun is directly overhead and entering the surface crack of the canyon.  It was 10 AM by the time I had gotten there and the deep shadows were disappearing, so I was having difficulty in capturing the deep purples and blues that I wanted. 

Here is where this ACR Smart Object technique comes in.  Using the steps outlined above I created two smart object layers in my Photoshop Palette.  Using the first layer, I open ACR and change the White Balance Temperature and Tint to the desired effect I'm looking for.  In my case, the Tungsten preset produced a great starting point. From there, I created a black layer mask on the second layer. Then, using a soft brush with a foreground color of white, I paint in the shadow area to reveal the blues and purples of the layer below it. 

Although I really liked the original Before image, I was able to accomplish what I was after using Adobe Camera Raw and Smart Objects.  If you decide the effect is a little too strong, you can always lower the Opacity of the second layer to blend back in some of the original color.