It is about 0.2 - 3.0 m in distance from the edge of the lens that a flash work with the following conditions.
ISO Auto
Taking a picture with wide end of the zoom lens
* The default setting of the GR DIGITAL is Flash Off.
For the details on Flash modes, how to use the flash, and Using the hot shoe (for external flash,) please consult the Camera User Guide in page 44, 45, and 46.