Nikon D300s manual Built-in Flash, 170

The Built-in Flash

The built-in flash has a Guide Number (GN) 17/56 (m/ft., ISO 200, 20 °C/68 °F). It supports i-TTL balanced fill-flash for digital SLR, which uses monitor pre-flashes to adjust flash output for balanced lighting not only when natural lighting is inadequate but when filling in shadows and backlit subjects or adding a catch light to the subject’s eyes. The following types of i-TTL flash control are supported:

i-TTL balanced fill-flash for digital SLR: Flash emits series of nearly invisible preflashes (monitor preflashes) immediately before main flash. Preflashes reflected from objects in all areas of frame are picked up by 1,005-pixel RGB sensor and are analyzed in combination with range information from matrix metering system to adjust flash output for natural balance between main subject and ambient background lighting. If type G or D lens is used, distance information is included when calculating flash output. Precision of calculation can be increased for non-CPU lenses by providing lens data (focal length and maximum aperture; see 0 195). Not available when spot metering is used.

Standard i-TTL flash for digital SLR: Flash output adjusted to bring lighting in frame to standard level; brightness of background is not taken into account. Recommended for shots in which main subject is emphasized at expense of background details, or when exposure compensation is used. Standard i-TTL flash for digital SLR is activated automatically when spot metering is selected.

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DISO Sensitivity

i-TTL flash control can be used at ISO sensitivities between 200 and 3200. At values over 3200 or under 200, the desired results may not be achieved at some ranges or aperture settings.

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