One thing I've loved about Lightroom since I began using it is the ability to select two images and "Edit them in photoshop as layers" which opens a whole bag of options in terms of creativity and editing.
One example of said creativity is the ability to quickly and easily change colors on parts of an image without having to know a whole lot about Photoshop. For this post, I'll do background changes in about 5 min.
DISCLAIMER: You need to have LR and PS to do things exactly as I do them here. And LR needs to have the new Radial gradient tool.
1. First I start off with this image. Whilst good for the purpose it was made, I wanted to see how I could spice up the image a bit. After doing the basic corrections that are done on all images I ended up with the image on the right as the starting point:
I decided I wanted to change the background to a more fun color. I settled on purple.
1. What I did first was right-click on the above image (#1) in LR and create a "Virtual copy" which makes an exact copy of the image.
2. Then, on the Virtual Copy, I simply changed the "Tint" slider which is found in your Develop Module. It's found under the "Temp".
I slid it around until the background looked nice. Didn't care about how it affected rest of image.
3. Then, I had image #1 and image #2 in Lightroom. I selected them both by holding Ctrl and clicking on them both.
4. Then I right-click on one of them and chose the "Edit" option and then pick "Edit in Photoshop as Layers".
So now you have one image open in PS with the two images as layers. I always place the colorized one on top.
5. Then I select the top layer (image #2), right-click on it and make it a "Smart Object" by choosing "Convert to Smart Object" as seen HERE.
6. Then I got to "Layer" and "Reveal All". HERE is a screen shot of what you should see.
7. Then click on the white box next to the layer on the right to select it.
8. Then you chose the Brush tool. Pick a soft edge brush. Then chose black as the color (see the easy white/black boxes in this screen shot.) and start painting over the subject.
You'll see that the subjects natural color from the layer below starts coming through. Do that until you have the subject fully showing and the background left purple. This might take some time to be done properly. You can easily switch the brush color to paint back over areas you messed up to bring back the purple. That's the beauty of Smart Objects.
When done, save the image. It should show up in LR looking like the above. It's now Image #3
9. Then go back to LR. You should now have the image with the purple background in LR as it should auto update that library.
10. Create another Virtual Copy of that.
11. Next use the new radial gradient tool to create a bright spot like the one to the right. My intent is to create a spot as if I had a flash on the background. I don't care how it looks on her face because we're not going to use that. TIP: You may have to reverse the gradient to get it to work.
12. Then, again, Ctrl-click on this new image as well as the one before with the purple background and "Edit in PS as layers".
13. Place this image #4 below Image #3. Use the same "Convert to smart Object" technique but this time painting where you want to reveal the "spotlight background" from Image #3.
14. Once you're satisfied with your "painting" which should have revealed the brightened purple background behind her head, save it and it should appear in Lightroom looking like the image to the right (Image #5)
15. Then you can do some more fine tuning if needed.
It's by no means perfect. Using proper lighting and preparing to achieve this look BEFORE taking the photo is most important, but this method at least gives you some flexibility in changing an image that fit it's initial purpose into something different and perhaps a bit more dynamic. And best, it's not difficult for those of us who are PS challenged.
DISCLAIMER #2: I believe this technique works best on images such as this where there is a shallow DoF where it's not so important to do perfect edging technique With a sharp edged image this would probably take longer.