Hot-Shoe Flashes: TTL, Guide Number and Wireless

Dedicated TTL or universal slave: matching the camera

A dedicated flash talks to the camera through the hot-shoe contacts, so exposure (TTL), flash sync and zoom happen automatically. Contacts and protocols differ between camera systems, so a dedicated flash for one system, listed by name or code such as E-TTL II, will not work fully on another. A universal digital slave flash fires with a light pulse from another flash and is manual only. Check the stated camera list and the wireless system it uses.

Guide number, bounce head and wireless control

Guide number measures power: GN60 reaches farther or works at smaller apertures than GN28, though it is larger and heavier. A head that tilts and swivels lets you bounce light off a ceiling or wall for softer results, which a fixed head cannot do. Radio wireless control, as in the radio-control models listed, lets you trigger off-camera flashes without line of sight, while optical triggers need a clear view. Check recycle time and the battery type, usually AA cells.

Questions about Hot-Shoe Flashes: TTL, Guide Number and Wireless

What does TTL mean on a flash?

TTL means through the lens: the camera fires a pre-flash, measures the reflected light and tells the flash how much power to use. It gives reliable exposure in changing scenes, while manual mode gives consistent results once you know the settings.

Can I use a flash from another maker on my camera?

Physically it may fit the hot shoe, but TTL and wireless functions need a compatible system. In manual mode a flash can often still fire. Avoid very old flashes with high trigger voltage, which can damage a modern camera.

Is the built-in flash enough?

For fill light at close range, yes. A hot-shoe flash is more powerful, can bounce light for softer shadows and avoids the flat look of direct flash. It also reaches farther at a given aperture and uses its own batteries, sparing the camera's.