#1. "RE: Which is Fill Flash equivalent on D70?" In response to Reply # 0
Generally, Fill-Flash is available when:
1. You are in Matrix Metering 2. You are using a D/G lens (which puts you in 3DMBFF) otherwise use a non-D lens (which puts you in MBFF). 3. You are in Front Curtain Synch - the flash symbol in the camera LED display should just show the box and the flash symbol (no red-eye, no REAR, no SLOW/REAR).
Shoot a few test shots if you're using the 18-70 kit lens with the hood on to determine the vignetting. The manual will probably tell you what usable focal lengths are with the built-in flash.
#2. "RE: Which is Fill Flash equivalent on D70?" In response to Reply # 0
assuming it's like all the other current nikon SLRs, the D70 measures the effect of the flash 'real-time' as it flashes. the camera just continues to dump flash into the picture until it determines that the correct exposure is achieved. in this way, the D70 does fill flash automatically. just pop up the flash when you want it. of the 5 choices you give up there, i suspect they'll all automatically fill flash except maybe the slow syncs.