Nikon D3s Body Only User Manual - Page 224

FV Lock This feature is used to lock flash output, allowing photographs to be recomposed without changing the flash level and ensuring that flash output is appropriate to the subject even when the subject is not positioned in the center of the frame. Flash output is adjusted automatically for any changes in ISO sensitivity and aperture. FV lock is available with CLS compatible flash units only. To use FV lock: 1 Assign FV lock to the Fn button. Select [FV lock] for Custom Setting f4 ([Assign FUNC. button] > [FUNC. button press], pg. 333). 2 Attach a CLS-compatible flash unit. Mount an SB-900, SB-800, SB-600, SB-400, or SU-800 on the camera accessory shoe. l 3 Set the flash unit to TTL or AA mode. Turn the flash unit on and set the flash mode to TTL or AA. See the Speedlight instruction manual for details. 198