Today's "trick" is pretty easy. I went to two different baseball games a week or so ago. One was a "vintage" game, played with rules from 1887 and the other was a game for the NECBL (New England Collegiate Baseball League).
I stood in about the same spot for a portion of each game, shooting a combination of batter, catcher and umpire. When I noticed the similarity between the shots of each game I knew I had to play.
Adobe Photoshop CS6's Auto Align Layers made the basic job easy. From Adobe Photoshop Lightroom 4, Photo/Edit in/Load As Layers in Photoshop was used to get the two images over to CS6. The next step was to select both Layers in the Layers Panel. (Choose one and Shift Click the other Layer.) Then it's a simple matter of using Edit/Auto-Align Layers to get everything squared up.
Once both Layers are aligned, put a Layer Mask on the uppermost Layer. Then grab the Quick Selection Tool (W). Click and hold while running the QST down the players of the top Layer. Clean up the Selections in any way you're comfortable. The most accurate method (IMHO) is using the Refine Selection dialog box. What I did was Save Selection for each player on the top Layer. Once the Selections are made, highlight the Layer Mask and add each selection to the Mask. Invert the Mask if necessary to have the players show through.
Match up the colors in various parts of the scene and you're done (if you want to be). I did one more step and took out all the fence poles and posts using Content Aware Fill. Just as a note: I've seen a lot of blogs and websites talk about the improvements in CS6. I haven't seen anyone comment on the improvement made to Content Aware Fill. In the CS5 version, if your selection was near something totally different from what you were trying to fill you'd end up with a strange fill. In CS6, you can bring the edge of the selection right up to something with some contrast and CS6 figures out that the "foreign object " should not be included in the Fill. Pretty amazing.