<p>I have K-10 and Sigma EF -500DG SUPER. For high speed sync, the lcd panel on the flash displays FP. As per Sigma manual any mode on the flash with FP indicator can be used for high speed sync. Similarly on the camera, too, any mode can be set. However, I am confused about the camera mode. In AV mode, the shutter is automatically set at 180. In TV mode, though higher shutter can be set there will be no control over aperture. The only way out appears to be manual mode-when shutter/aperture both can be set. But then proper exposure would be trial/error exercise. I would like to know- which mode and settings to use when the flash is in FP mode.</p>