110Taking Photographs—Flash PhotographyD-TTL Flash ControlD-TTL flash control is available when an optional SB-series 80DX, 28DX, or50DX Speedlight is mounted on the camera accessory shoe. D-TTL flash con-trol is not available with other optional Speedlights. The type of flash controldepends on the lens attached:DescriptionLens3D Multi-Sensor Balanced Fill-Flash for Digital SLR: Speedlightemits a series of nearly invis i ble preflashes (moni tor prefl ash es) im-mediately before main flash. Preflash es reflected from objects in allareas of frame are picked up by five-segment TTL flash control sensorand ana lyzed in combination with information from matrix meteringsystem to adjust flash output for natural balance between main subjectand ambient background lighting. Not available when spot meter ingis used.Type G or DCPU lensMulti-Sensor Balanced Fill-Flash for Digital SLR: As above, exceptthat distance information is not included in regu lat ing flash output.Precision of calculation can be increased for non-CPU lenses by provid-ing lens data (focal length and maximum aperture; 124–127). Notavailable when spot metering is used.OtherlensesStandard TTL Flash for Digital SLR: Flash output is adjusted to en-sure that main subject is cor rectly exposed, without taking the back-ground into account. Rec om mend ed for shots in which main subjectis empha sized at the expense of background details, or when exposurecompensa tion is used. Standard TTL fl ash for digital SLR is activatedautomatically when spot metering is selected.All types
