Cross-type AF Point
A phase-detection point sensitive to detail running in both horizontal and vertical directions.
Measured in
count
In depth
A single-axis point can only measure contrast running perpendicular to its sensor line, so it fails on a subject whose only detail runs the same way — a horizontal line above a horizontal sensor strip. Cross-type points pair two perpendicular arrays and so work on any edge orientation. Their count and distribution across the frame was a headline specification of DSLR autofocus modules.
Examples in practice
A horizontal-only point struggles on a level horizon, while a cross-type point in the same position locks immediately.