A method and an apparatus are described for determining parameters of a contact between bodies occurring within an activity. A digital camera directed towards a target area during the activity captures image frames including infra red image data. Structure for comparing image data for multiple temporally spaced frames with image data of a reference datum records any localized infra red emission appearing in at least one incident frame. The image data for at least one of the incident frames is analyzed to determine at least one parameter of the contact, and the image data for the incident frame is recorded. Visual display means displays the incident frames including the image data in the IR spectrum to enable visual inspection of the activity in the target area at the time of the incident frame and that gave rise to the contact producing the infra red emission.