Hot Spot in Cricket: How Infrared Imaging Detects Edges

Hot Spot is an infrared imaging system used in cricket broadcasts and, occasionally, in the Decision Review System to determine whether a ball has made contact with the bat or pad. When the ball brushes the bat, friction generates heat on both surfaces; infrared cameras capture this heat signature as a bright spot. It is particularly useful for thin edges — the kind that do not produce an audible click — on caught-behind or caught at slip decisions.

How Hot Spot Works

Two high-speed infrared cameras are positioned at each end of the ground, one on either side of the wicket. They continuously image the bat, pad and ball in the infrared spectrum. When a review is taken, the footage is slowed down and the exact moment of contact is examined. A faint white mark on the bat edge confirms contact; a mark on the pad confirms pad-hit rather than bat-hit. The process takes seconds and is displayed on the broadcast feed.

Limitations of Hot Spot

Hot Spot is not infallible. Contact between ball and bat generates heat, but so does ball-on-pad and ball-on-ground contact. In cool weather, heat signatures dissipate quickly and very thin edges may not register. Modern bats with polymer or fibre-glass coatings can also reduce heat transfer. Cases of balls apparently not hitting the bat but still showing a mark — and edges producing no mark — have raised questions about the system's reliability in all conditions.

Hot Spot vs UltraEdge

UltraEdge (a real-time Snickometer based on the Hawk-Eye system) has largely replaced Hot Spot in many DRS implementations. UltraEdge shows an audio waveform of bat-ball contact that is highly sensitive to sound spikes; it works in all weather conditions and does not require specialised infrared cameras. When both systems are available, they are used together: an audio spike combined with a Hot Spot mark provides strong confirmation.