The Xiaomi Mi 10 Youth is the most affordable, thinnest phone with a periscope zoom lens yet - the company posted a detailed explanation of periscopes and how the Youth edition managed to claim those titles. First of, you may have heard the term focal length used to describe the zooming capabilities of a lens. It comes from the distance between the lens and the image sensor, which is proportional to the distance from the lens to the object being photographed. But since modern phones are not much thicker than 10mm or so (even including the camera hump), focal length on traditional...