The xBeam system is a bit bulky, but would you carry it around if it guaranteed shots with perfect focus? It operates by using two lasers in an "X" shape to detect when an object (well, the subject of the image) is exactly at the intersection of the beams. The mounted camera must be pre-focused on the intersection and fitted with a neutral density filter, as the shutter needs to be open for at least a tenth of a second once the object takes its place in the center of the image. When the controller detects that both beams are simultaneously interrupted, it shuts them off (so they don't end up in the image) triggers the camera's shutter, and then fires the flash. Since the flash is much brighter than the ambient light, the photo comes out well exposed even with the neutral density filter.