Flashing

Flashing is a term used in several distinct contexts, generally involving a brief emission of light or a protective layer designed to keep moisture out. The precise meaning depends on the field, with common uses in construction, lighting and photography, and computing and electronics.

In building, flashing refers to thin sheets of metal (such as aluminum or copper) or flexible membranes installed at joints where components meet, including roof valleys, around chimneys and vents, and along wall-to-roof transitions. The purpose is to direct water away from seams and prevent penetration, helping to maintain the structure’s integrity. Flashing must be continuous and properly sealed to work effectively; poor installation or deterioration can lead to leaks and damage.

In lighting and photography, a flash is a device that emits a brief burst of bright light to illuminate a subject. Built-in camera flashes provide quick illumination, while external flashes or studio strobes offer greater power and control. Modern cameras use TTL (through‑the‑lens) metering for automatic exposure, though photographers may also set manual power and distance. The flash must synchronize with the shutter to avoid under- or overexposure.

In electronics and computing, “flashing” can mean writing new firmware to a device’s flash memory, a nonvolatile storage medium used in many digital devices. Firmware flashing is common during updates but can render a device inoperable if interrupted. Flash memory is also used in USB drives, SD cards, and solid-state drives. In signaling, a flasher circuit produces blinking lights, such as turn signals and hazard lights.