Comes from their website: "To create HDR pictures, you need to start with at least two photos, each capturing a different range of brightness in a scene. The challenges lie in merging those pictures and keeping the parts that you care about in each. If you don't have a tripod - and who does with the iPhone - it's hard to keep the camera perfectly still between taking the pictures. For TrueHDR, we automatically match the details of the two photos and align them. We then use sophisticated techniques to figure out the best parts of each image, and selectively adjust and merge them to look good together. And in the end, you're going to be looking at the result on computer screens that can only display a limited range of tones, so our calculations optimize the image for display on your screen. "