Marc Carmen on Instagram: "The Spherometer. Not only is it fun to say, but it is an essential tool in my shop. Basically, it’s a tripod with a dial indicator acting as a fourth, central leg. I use it to measure the curvature of a lens between each grinding stage. This meticulous measurement is vital to ensure that after each grinding step, the convex lens’s curvature matches perfectly with the concave grinding or polishing tool I’ll be using next. Here I’m taking a blank from curve generation>ro