A conversation with Marc Levoy unlocked one thing that has puzzled me for a while: why don’t we see cell phones with dual imaging system to offer different focal lengths, even if we only get a binary choice? Marc pointed out that form factor is the biggest problems. Cell phones already struggle to fit a moderate wide angle lens in their limited depth. The iPhone 6 even got a lot of criticism for its bulging lens. A telephoto would be naturally much deeper and wouldn’t fit directly. Folded optics has been attempted (e.g. Minolta Dimage, Apple patent, UCSD version, and course Light L16) but generates its own problems, mechanical amongst others. At least with traditional imagers and thin cell phones, we’re stuck with wide-ish angle. Unless you follow XKCD and use a side-facing camera.