This series was taken over a 2.5 second period. The trout was very steady and graceful in the approach, it barely made a ripple as it broke the surface to take the fly. You can often tell what the trout are feeding on just by watching how they take the fly. If they splash a lot, they may be taking caddis. If they seem to roll out and into the water, they may be scooping up clumps of midges.
It is just as important to watch how they feed below the surface. Constant movement back and forth usually means active feeding. A trout lying very still in quiet water may be resting, and might be more difficult to catch.