Pentax K-5 Operating Manual page 6

Using the Flash
This chapter provides details on the built-in flash of 1_-5
and describes how to take pictures with the external flash.
Flash Characteristicsin Each Exposure
Mode .................................................................... 182
Distance and Aperture when Using the
Built-in Flash ....................................................... 185
Lens Compatibility with the Built-in Flash ....... 186
Using an External Flash (Optional) ................... 187