A + B = C (or AB, I don't know, I was never good at math.)
I have a tripod, but I don't always have all the time in the world to setup and (depending on the location) clear the crowds out of my way. In order to get the shot I want I've been using this method of taking 2 photos (1 taken by you and the other taken by your partner in crime) and combining them in Photoshop. Here is how I do it:
Out in the field (Aka wherever you are with your camera!)
1. Positioning: Position your friend in the spot you want them and take the shot. Before either of you move, mark your spot with a stick or purse- anything really. Mark their spot as well.
2. Switch spots: Your friend should now be behind the camera standing in the exact same spot that you'd been. You should stand either a step to the right or left of where your friend had been standing.
Easy right? If you're using a digital camera you can scroll through the shots to make sure your shots line up well enough. They don't need to be perfect.
On your Computer in Photoshop:
3. Open both photos in Photoshop:
4. Copy/Paste/Opacity: Copy Image B and Paste it onto Image A. Reduce the opacity of Image B to 50% so you can see hints of both images.
5. Move Image B: Using the "Move Tool," move Image B to exactly where you want it- to a spot that makes sense. Don't worry that the background might not match up perfectly.
6. Select/Inverse/Delete: Using the selection tool ("rectangular marquee tool") tool, make a little square around the person in Image B. Now go to "select" > "Inverse" and then press "delete." This will delete the entire Image B except for the person and a little space around them.
7. Erase: First, bring the "opacity" of Image B back up to 100%. Select the "Eraser tool" and reduce the "size" so that it's small enough, like a real pencil eraser or smaller. Reduce the "hardness" to around 70%. Zoom in so you have a good view of your workspace. Proceed to erase the extra background so that you're left with the person. Don't worry about making exact lines, since the person in image A and in B were photographed in the same place, the background colors will likely mesh well even if the 2 backgrounds don't match completely.
8. Flatten: When you're happy with your erasing job, flatten the image into 1 image. "Layer" > " Flatten image." That's it!
Now you can edit your image like you normally would if you like. I hope this was helpful! If you have any questions please feel free to ask either in the comments or through e-mail (firstname.lastname@example.org)
Some other examples:
Let me know if you try it out! I'd love to see!