There's been a new feature and functionality on the web that I've noticed recently that I believe is both as good looking as it is functional. It's an image effect where what appears to be a single image has a vertical line dividing it that can be moved or slid from one side to another that reveals another image. In the implementations I've seen online as shown below, it frequently is used to show the differences between a "before" and an "after" photo of some sort.
In the example below that I saw on the BuzzFeed website, the functionality was used to show a "Then" and "Now" photo of the various cast members of the fantastic movie, The Princess Bride. What really makes this functionality stand-out in the example below is that the two photos that were used were sized and cropped appropriately so that the transition from one photo to the other appeared almost seamless. Facial features didn't shift or mis-align as you moved your mouse cursor from one side to the other.
In the example shown below, the functionality was used in an ad on Pandora, one of my favorite web site applications for listening to music while I'm working. In the usage on the Dodge ad you were able to slide the image to go from the old Dodge Challenger to the new Dodge Challenger with the slide of your mouse. Again, a very nice usage and effect. However, with the example shown below, you can see how the two images weren't quite sized and aligned quite as well so there was somewhat of a less-than-smooth disconnect between the two photos as you played with the slider.
Either way. This is a nice effect online. I'd like to see how it's done and maybe use it in the future somehow. I could have definitely used it in my previous post about the before & after photo of the original Cracker Barrel store in Lebanon, TN.