Ask UEFL - Judging a Fly Ball as Fair or Foul (Video)

In the wake of umpire Paul Nauert's fair-to-foul call in Pittsburgh, Jim asked about a rules interpretation in the MLB Umpire Manual concerning the definition of a fair ball. Due to Replay Review and the parallax angle effect, clarity was needed for video that could deceptively indicate a fair ball when the spherical baseball may or may not have actually touched fair territory (e.g., the foul line) when the ball first fell to the ground. No rule was changed in the making of this interpretation.

3D video illustrates the fair/foul parallax issue.

The new MLBUM interp states, "When in contact with the ground, a ball must be in contact with fair territory and not merely over fair territory in order to be adjudged to be fair," whereas the Definition of Terms (which hasn't changed) states, "A FAIR BALL is a batted ball that...first falls on fair territory on or beyond first base or third base."

Important: This analysis refers to a batted ball, in flight, that first touches the ground at or past first or third base. In the case of a bounding ball (e.g., a ground ball) that passes first or third base after first touching the ground in front of the base, any part of the ball that breaks any part of the "fair territory" plane extending upward from the foul territory-facing side of the base, at the point where the ball passes the front edge of the base, is a fair ball. This also applies to batted balls leaving the playing field in flight (any portion of the ball that breaks the fair territory plane as the ball leaves the field signifies a fair ball. This plane is usually signified by the existence of a metal foul pole).

Because Replay Review is all about camera angles and video playback, the interpretation cited above clarifies for the Replay Official that the camera angle alone should not be used to approximate where the ball landed: the Replay Official must obtain clear and convincing evidence to suggest that the ball actually made physical contact with the ground in fair territory (e.g., the chalk or painted white line) in order to confirm or overturn a fair/foul in the outfield-type review.

Hockey's parallax effect also affects baseball.

In other words, an aerial or angular view that merely suggests that the ball was over the line at the time of ground contact is not sufficient due to the possibility that the ball failed to make physical contact with the portion of the ground that is in fair territory.

In relation to the important disclaimer above, an overhead or top-down angle would be sufficient for a bounding ball or batted ball leaving the playing field in flight (fair/foul HR review) because both of those fair/foul judgments are made in relation to the ball's location when it passes a plane or boundary: no physical contact required (e.g., a potential HR hit over the height of the foul pole...a top-down look would indicate whether it was fair or foul, without requiring any physical contact with the pole itself).

This is similar to the parallax angle effect we previously discussed that can make a pitched ball appear to be a strike from one angle, but not another, or how a check swing can look different from two competing camera angles.
Related Post: Deceptive Angle - Woodring's Parallax Check Swing (6/6/18).

The following video thus illustrates the parallax effect for fair and foul balls in the outfield:

Alternate Link: Fair or Foul - Umpire's Parallax Angle for a Ball Over the Line (UEFL).