Panasonic Lumix G X Vario 12-35mm f/2.8 Pro Digital Lens Hood (Petal Design) (58mm) + NW Microfiber Cleaning Cloth.

A lens hood will help block out light that is coming into the lens and causing flare by striking the outer lens elements (the glass pieces that make up the entire lens) at a less than optimal angle. This is light that never would have made it to the sensor and isn’t needed. Instead, it causes those discolored spots you might have seen, shaped like the lens aperture (typically a hexagon or octagon). While lens flare also occurs from light coming directly into the lens, flare from off-angle light can be prevented.