Directional number (at ISO 100) of external flashes
Catalogue
The directional number (GN) is a key indicator of external flash performance. It expresses the maximum flash range in meters at ISO 100 and full power capacity. A higher directional number means a greater flash range and therefore the ability to illuminate more distant objects. For example, a flash with a directional number of 60 at ISO 100 will illuminate a subject at a distance of 60 metres at ISO 100. The directional number is important for judging whether the flash can adequately illuminate a scene, especially when shooting in large spaces or when soft light diffusion is needed when using diffusers or reflective surfaces.
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