My set up is this: Nikon D90 /Metz 50 Af1 Camera: Manual 1/60 f4 ISO 400 flash in commander mode (trigger only) flash shutter speed at 1/60th Flash: Manual Servo Problem: with the flash at 1/128th, triggered by the camera (also at 1/128), my exposure is "fine". Once I increase the power of the flash I get a dark (underexposed image). An incident light meter proves my flash out put is increasing. A shutter miscue has been suggested, but I'm stumped. I'm quite new to working with flash at this level, and it has me stumped as I work through Strobist's; Lighting 101. Has any one else run into this kind of 3rd party conflict? Any thoughts?